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467 Cards in this Set

  • Front
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Causative agent of nausea, vomiting (onset < 6 hr) after eating cold cuts, or potato salad, or mayonnaise, or custards?
Staphylococcus aureus
Rapid-onset food poisoning is mediated by what component of staphylococcus?
Enterotoxin
Tx of staphylococcal food poisoning?
Rehydration
Microbial cause of nausea and vomiting, +/- diarrhea (onset < 6 hr) after eating reheated rice?
Bacillus cereus
Bacterial spores are resistant to heat due to what component?
dipicolinic acid core
Microbial cause of nausea, vomiting, watery diarrhea w/ rapid (onset >6 hr) after eating reheated meat or gravy?
Clostridium perfringens
Most likely cause of persistent dyspepsia in a pt not receiving NSAIDs is
Helicobacter pylori
Increased risk of gastric adenocarcinoma and MALT lymphoma
H. pylori colonization
Indications to treat H. pylori-associated PUD
Presence of organism
Standard first-line abx for PUD due to H. pylori is
PPI + clarith + amox
Cause of acute onset of diarrhea with rice-water stools, vomiting, dehydration during travel to South America
Vibrio cholerae
Pathophysiology of cholera is due to what mechanism?
A-B toxin causes ↑ cAMP
Cholera pathogen is isolated from stool by culture on selective medium called
thiosulfate-citrate-buffered sucrose (TCBS) agar
The comma-shaped cholera organisms are microscopically similar to
Campylobacter
Tx of cholera involves
Rehydration (tet in severity)
Secretory diarrhea, fever and vomiting during travel are caused by
Enterotoxic E. coli
Secretory diarrhea w/ fatty, foul-smelling stools in campers, hikers; also day-care outbreaks is caused by
Giardia lamblia
Following ingestion of 15-25 cysts, excysted trophozoites adhere at brush border of enterocytes and contribute to malabsorption. TOW?
Giardiasis
Dx of giardiasis is confirmed by
Stool antigen (+)
Giardiasis is specifically treated with
Metronidazole
Protracted, secretory diarrhea w/ large fluid loss in AIDS is caused by (clue: acid-fast organisms)
Cryptosporidium >> Cyclospora > Isospora
Frank bloody diarrhea, after eating undercooked meats or drinking fruits drinks, is caused by prepared foods or water, contaminated w/
E. coli O157:H7
Pathogenesis of hemorrhagic enterocolitis caused by E. coli involves
Shiga toxin (a cytotoxin)
Complication of hemorrhagic enterocolitis in children
hemolytic uremic syndrome
Profuse diarrhea, fever, vomiting, and dehydration in infants is caused by
Rotavirus
Mechanism of rotaviral diarrhea involves
Villus destruction
Infantile watery diarrhea and fever are caused by
Adenovirus 40,41
Outbreak of nausea, vomiting, fever in adults is caused by
Norovirus
Cause of nausea/vomiting, abdominal cramps, diarrhea +/- bloody 12-48h after eating eggs or poultry or peanut butter?
Non-typhoidal Salmonella
Abx treatment in acute gastroenteritis due to Salmonella spp. is not warranted to avoid
carrier (in bile ducts) state
Abx used only to treat septic phase of salmonella gastroenteritis is
ciprofloxacin
Cause of fevers (>103°), headaches; macular rash on torso (“rose spots”) abdominal pain and little diarrhea later; PE: bradycardia; hepatosplenomegaly (+/-) in a pt with hx of travel (to tropics)?
Salmonella typhi
Cause of diarrhea w/ occult blood, abdominal cramping and fever, 2d after ingestion of poultry-contaminated salad
Campylobacter jejuni
Abx to treat campylobacter enteritis with high fevers in
pregnancy, and HIV is
Erythromycin
Cause of dysentery-like illness with fever + abdominal cramps, tenesmus + blood & mucus in children?
Shigella sonnei
Dysentery due to invasive Shigella spp. in elderly is treated with
Ciprofloxacin
Cause of dysentery-like illness (+/- pseudoappendicitis or pseudo-crohn syndrome) in the northern region after eating cheese
Yersinia enterocolitica
Cause of dysentery-like illness in a patient w/ hx of broad-spectrum abx use
Clostridium difficile
Clostridium difficile-associated diarrhea (CDAD) is mediated by toxins
A (enterotoxin) + B (cytotoxin).
Lab confirmation of CDAD does not require stool Cx, but is based on
EIA for stool toxins A or B
Besides rehydration and cessation of inciting meds, CDAD is treated with
Metronidazole (mild) or oral vancomycin (severe/relapse)
Health-care associated (nosocomial) spread of Clostridium difficile diarrhea and protracted outbreak is due to
Fecal-oral and/or contact w/ environmental spores
Hx of abdominal pain, tenesmus, stools with mucus + blood in a patient, who recently traveled to tropics; CBC: eosinophilia. TOW?
Amebic dysentery
Stool microscopy to confirm amebic dysentery should reveal characteristic trophozoites of Entamoeba histolytica w/
endocytosed RBCs

(distinction from luminal
ameba)
Rx of amebic dysentery involves
Metronidazole + iodoquinol
Abscesses in liver or peritonitis in travelers w/ or w/o hx of amebic dysentery is confirmed by
Serology for E. histolytica
A boar hunter develops dysentery after eating meat at campsite; O & P test should reveal a ciliate parasite, known as
Balantidium coli
Most likely cause of chronic abdominal pain, diarrhea; intestinal obstruction; cholangitis; liver abscess, in children
Ascaris lumbricides
Ova & Parasite test using microscopy for oval eggs (with a thick coarse shell) in stool confirms
ascariasis
A child has stomach ache, distended abdomen, poor appetite. “Pearl-colored earthworm”-like organisms in the stool. Major immune response against this infection?
IgE
DOC of ascariasis is
Mebendazole
Vomiting, cramping, diarrhea, epigastric pain, weight loss in an immigrant from developing country is caused by
Strongyloides stercoralis
DOC of strongyloidosis is
Ivermectin
Pt w/ AIDS (low CD4+ counts) develops pulmonary infiltrates (+ eosinophilia) and/or gram negative sepsis. TOW?
Invasive strongyloidosis
Weakness, fatigue, lightheadedness, dyspnea, pruritis; pallor; iron-deficiency anemia; eosinophilia (hx of outdoor activity). TOW?
Hookworm (Necator americanas) infection
Fever, periorbital edema, subconjunctival hemorrhages, muscle weakness, and rash, after eating undercooked pork (Lab: eosinophilia., .CPK, .LDH &). TOW?
Trichinellosis
Abdominal pain, bloating, altered appetite after ingestion of sushi. CBC: megaloblastic anemia; leukocytosis/eosinophilia. TOW?
Diphyllobothriasis (fish tapeworm)
Dx of tape worm infection is confirmed by
Proglottids in stool
Tape worm infections are treated with broad-spectrum agent
Praziquantel
Cause of fever, lymphadenopathy, hepatosplenomegaly in an immigrant from Africa or Orient; pt recalls wading in stagnant water. RUQ ultrasound (+); CBC: eosinophilia.
Schistosoma mansoni (Africa)
S. japonicum (Far East)
Microscopy of stool in chronic stage of schistosomiasis reveals
Large eggs with lateral spine.
Chronic stage of schistosomiasis is treated with
Praziquantel
Patient with acute jaundice is HAV IgM (+); household contact should receive for prophylaxis
Inactivated HAV vaccine
Patient with jaundice for < 1 week has HBsAg (+), Anti-HBc IgM (+). TOW?
Acute HBV infection
Multiple sex partners, IDU, infants born to infected mothers are risk groups for which hepatitis virus
HBV
This is an enveloped, double stranded DNA virus w/ ss-break; transmitted by infective body fluids. TOW?
HBV
This asymptomatic man has hep serology profile of HBsAg (-), Anti-HBs (+), Anti-HBc IgG (+), Anti-HBc IgM (-). TOW?
Resolved hepatitis B
This man has jaundice and is HBsAg (+) > 6 months, Anti-HBs (-), HBeAg (+), Anti-HBc IgG (+), HBV DNA > 20,000 IU/ml. TOW?
Chronic active hepatitis B
This man has jaundice and is HBsAg (+) > 6 months, HBeAg (+) and evidence of necroinflammation. He should receive
Peg-IFNa 2a + lamivudine
(or cidofovir)
This man has no jaundice, but HBsAg (+) >6 months, Anti-HBs (-), Anti-HBc IgG (+), HBeAg (-), persistently normal ALT. TOW?
Inactive HBsAg carrier
This man, at the time of annual physical exam, reveals Anti-HBs (+) and other markers are (-). TOW?
HBV immunized
Virologic confirmation of chronic jaundice in a HBV-immunized pt w/ IDU or hemodialysis is based on
HCV RNA > HCV IgG
More chronicity of HCV (than HBV) is due to immune-evasive quasispecies generated during replication (in blood) of
error-prone HCV RNA virus
Fulminant hepatitis in a patient, who has multiple sexual partners and is HBsAg (+); HBcIgM (-), can be fatal due to what?
HDV superinfection
Cause of acute onset of jaundice, nausea, right-upper quadrant pain, hepatomegaly in pregnant women in India
HEV
Fever, arthralgia, carditis, polyarthritis, chorea, erythema
marginatum; elevated WBCs or ESR/CRP. Clinical Dx is
confirmed by
Rising ASO titer
Type II hypersensitivity due to molecular mimicry in a
immunological sequel of streptococcal pharyngitis causes
Acute rheumatic fever (ARF)
ARF is diagnosed and treated with
Anti-streptolysin O (ASO) titer and benzathine penG.
A man with IDU has flu-like symptoms; 1-3 minor peripheral signs: conjunctival hemorrhage, Janeway lesions, Osler nodes, Roth spots, plus vegetation in tricuspid valve. Blood Cx (BCx) should yield
S. aureus
A pt w/ hx of extraction of impacted tooth 3 weeks ago now has subacute (native, mitral-valve) endocardits. BCx should yield
Viridans streptococci.
A pt w/ hx of St. Jude bypass 2 months ago has now subacute bacterial endocarditis. BCx should yield
Staphylococcus epidermidis
A pt with AIDS and recent hx of UTI has now subacute, native mitral-valve endocarditis. BCx should yield
Enterococcus faecalis (or faecium)
DOC of acute endocarditis in patient with IDU due to sensitive S. aureus (MSSA).
Nafcillin +gentamicin
DOC of acute endocarditis in patient with IDU due to resistant S. aureus (MRSA).
Vancomycin + rifampin
DOC of subacute, native mitral-valve endocarditits due to viridans streptococci.
PenG +/- gentamicin
DOC of subacute, prosthetic-valve endocarditis due to
Staphylococcus epidermidis
Vancomycin + gentamicin
DOC of subacute, native mitral-valve endocardits due to
Enterococcus faecalis (or faecium)
High-dose ampicillin + gentamicin
Patient with enterococcal bacteremia fails to respond to
vancomycin. MOR of the organism
D-Ala-D-Ala is changed to D-Ala-D-lac
Hx of catheter-related endocarditis, involving prosthetic or native valves. BCx (+) for budding yeast. Pt does not respond to AmphoB or fluconazole; should receive
Caspofungin
Patient with colon cancer has bacteremia due to
Streptococcus bovis
Cause of febrile, malaise, arthralgia, dyspnea, edema, palpitations. ST/T wave change, heart block, dysrhythmias; CXR: cardiomegaly
Coxsackievirus > echovirus > Trypanosoma cruzi (Chagas)
Cause of runny nose, red throat, and nasal pus
Rhinoviruses
Rhinoviruses and enteroviruses belong to picornavirus family, but the rhinoviruses differ from enteroviruses on
Growth at 22oC/noninvasive
Rhinovirus receptor in the nasal passages and upper
tracheobronchial tree is
ICAM-1
Rhinovirus, influenza, parainfluenza, coronavirus, RSV,
metapneumovirus, and adenovirus all cause
Upper-respiratory infections
(URIs)
Sinusitis, otitis, laryngitis, exacerbations of bronchitis and asthma are mostly secondary to
Viral URIs
In HEENT, Streptococcus pneumoniae, non-typable Haemophilus influenzae, Moraxella catarrhalis all cause
Acute otitis media (AOM) & sinusitis
AOM and sinusitis are empirically treated with amoxicillin + clavulanate. Why use clavulanate?
Haemophilus and Moraxella are ß-lactamase producers
Cause of pharyngeal pain, dysphagia, fever; red throat + purulent exudate that responds to penicillin
Streptococcus pyogenes (aka: Group-A ß-hemolytic
Streptococcus = GABHS)
GABHS is differentiated from GBBHS by what?
Bacitracin sensitivity
Common mode of acquisition of URI due to Streptococcus pyogenes?
Infective droplets
Major virulence factor with anti-phagocytic function of
Streptococcus pyogenes
M-protein fibrils
Damage in posterior pharynx and tonsils due to
Streptococcus pyogenes is associated with what host response?
Pyogenic inflammation
DOC of acute bacterial pharyngitis in a pt w/ Pen allergy
Erythromycin > clindamycin
Pyogenic complication of streptococcal pharyngitis
Tonsillar abscess
Toxigenic complication of streptococcal pharyngitis
Scarlet fever >> TSS (rare)
Immunologic complication of streptococcal pharyngitis
Acute rheumatic fever (ARF)
Cause of fever, red throat + purulent exudate -
pseudomembrane with lymphadenopathy, in a pt w/ questionable immunization
Corynebacterium diphtheriae
Gram/special stain of Corynebacterium diphtheriae should reveal
Gram(+) rods in palisade arrangements/metachromatic
granules
Virulence genotype of Corynebacterium diphtheriae is
acquired by
Transduction (phage mediated transfer of exotoxin gene)
Isolate on tellurite agar culture of throat swab for a cause of diphtheria is confirmed by
Immunodiffusion (ELEK) assay for toxin
Mechanism of action of exotoxin of Corynebacterium
diphtheriae
ADP ribosylation of EF-2
(inhibits protein synthesis)
Damage to pharynx and cardiac myosites due to
Corynebacterium diphtheriae is mediated by
Cytotoxicity of A-B toxin
Virologic Dx of URI symptoms, fever; red throat + purulent exudate; hepato-splenomegaly, lymphadenopathy, in a teenager, is confirmed by
heterophile antibody (+)
Host cells preferentially infected by EBV are
B cells
EBV is biologically similar to what class of viruses?
herpes viruses
Host immune system controls the EBV infection, mediated by
CD8+ T lymphocytes
Rash occurs following which antibiotic(s) to treat infectious mononucleosis?
amoxicillin
Burkitt's lymphoma in some African population is a B-cell
tumor due to oncogenesis by
EBV
Nasopharyngeal carcinoma, a B-cell tumor that is common in the Oriental population that consumes preserved fish, is due to oncogenesis by
EBV
Heterophile-negative infectious mononucleosis syndrome is due to ?
CMV
Gram-positive bacteria that cause acute otitis media (AOM)
Streptococcus pneumoniae
Gram-negative diplococci bacteria that cause AOM
Moraxellar catarrhalis
Gram-negative coccobacilli bacteria that cause AOM
Haemophilus influenzae
> 7 days of nasal obstruction, rhinorrhea; purulent nasal
drainage + frontal pain/tenderness is treated with
Amoxicillin & Clavulanate
DOC for acute mastoiditis in a young child is amoxicillin & clavulanate; why?
Same etiology as AOM
Cause of “seal-like barking” cough + episodic aphonia w/
symptoms of URI in a child
parainfluenza virus
Gram-stain-nonreactive organism that causes redness;
purulent discharge at lid margin/eye corners, in a newborn
Chlamydia trachomatis
Most common cause of redness; tenderess; hyperpurulent d/c; eye stuck shut in AM, lid edema. Gram stain (+)
Staphylococcus aureus
Cause of pharyngitis, conjunctivitis, fever with rhinitis, and cervical adenitis in a child.
Adenovirus
Cause of burning, gritty feeling in eyes; diffuse conjunctival injection & profuse tearing + preauricular LN.
Adenovirus
Cause of foreign body sensation, lacrimation, photophobia, conjunctival hyperemia, and ulceration
HSV-2>>1
Cause of severe pain and skin lesions in dermatomal pattern involving the ophthalmic division of the trigeminal nerve.
VZV
Cause of painful, swollen, red eyes, with conjunctival
hemorrhaging and excessive tearing in an outbreak
Enterovirus
Cause of chorioretinitis in AIDS, but CMV antigen (-)
Toxoplasma gondii
Cause of painful keratitis, chronic corneal ulcers in contact lens users, unresponsive to abx.
Acanthamoeba spp.
In an infant w/ ?immunization, 2 wks of paroxysmal
coughs, inspiratory "whoop" + post-tussive emesis. TOW?
Bordetella pertussis
Pertussis toxin inhibits chemotaxis via downregulation of
C3a/C5a receptor, resulting in?
lymphocytic leukocytosis in CBC
Three major virulence factors of “whooping cough”
pathogen?
ADP-ribosylating toxin; tracheal cytotoxin; hemolysin
Cause of fever + drooling, stridor, dyspnea in a child w/
?immunization (pt appears septic)
Haemophilus influenzae b
Major virulence factor of Haemophilus influenzae
associated with pneumonia and meningitis
Capsular polysaccharide (antiphagocytic and anti-C3b)
Since, absent spleen places host at increased risk for
invasive H. influenzae infection, pre-exposure prophylaxis prior to elective splenectomy is ?
Hib immunization
Cause of acute exacerbation (cough, purulent sputum) in pt with chronic bronchitis (COPD); CXR: R/O pneumonia; Lab: sputum reveals Gram-negative coccobacilli.
Haemophilus influenzae (non capsular types)
Tx of AECB, caused by an organism that needs NAD +
hematin for growth; ß-lactamase (+), is
Ceftriaxone (severe) > Amoxicillin-clavulanate (mild)
Most common cause of lower-respiratory infections in
neonates (babies < 4 wk)?
Streptococcus agalactiae
(aka: group B streptococcus)
Complicated illness in a newborn of a GBS-colonized
mother is
Sepsis or meningitis
A mother colonized (recto-vaginally) w/ GBS is at risk for
preterm baby or premature membrane rupture. She should receive
Ampicillin
An elderly comes up with an abrupt-onset fever, myalgia,
headache, malaise, dry cough, sore throat and rhinitis, in winter. Illness could have been prevented w/ ?
annual influenza vaccine
Annual influenza vaccine protects at-risk subpopulation w/ 60% immune protection, and is composed of what 3 viruses?
A:H1N1 + A:H3N2 + B
Secondary spread of influenza occurs in a crowded setting (within 6 feet of infected person) via
respiratory droplets
Annual vaccine to prevent influenza is needed due to
antigenic drift. This occurs due to what genetic mechanism?
Mutation
Occasionally serious pandemic of influenza occurs due to antigenic shift. This occurs due to what genetic mechanism?
Reassortment of 8 genomic
segments
DOC of pts with influenza <48 hours is
Oseltamivir
Bacterial superinfection, causing pneumonia, after influenza occurs in elderly (in LTCF) due to what?
S. pneumoniae > S. aureus
A seriously ill young adult w/ necrotizing pneumonia,
poorly responding to vancomycin, should get
Linezolid
Cause of febrile illness + bronchiolitis in an infant; BAL
viral culture (+).
Respiratory syncytial virus
(RSV)
RSV causes seasonal, nosocomial pneumonia outbreaks in the pediatric units via
Contact spread
Pathophysiology of asthmatic Sx + Sn in bronchioles in
high-risk infants due to RSV involves
type III hypersensitivity
Inhaled anti-viral drug used in the sickest infants with
bronchiolitis is
Ribavirin
Insidious onset of fever, dry cough, malaise and sore throat in young adults. CBC: anemia; CXR: diffuse infiltrates. TOW?
Mycoplasma pneumoniae
Dx of “walking pneumonia” in older children and young
adults, while waiting for serology, is supported by
cold agglutinin (IgM Ab against RBCs) titer =1:32
ß-lactam abx is ineffective for Tx of mycoplasma
pneumonia because
Wall-less bacteria
A male child with mycoplasma pneumonia now has
systemic rash, covering 10% of his body. TOW?
erythema multiforme (SJS)
Cause of upper respiratory Sx, slow onset of cough
(laryngitis) >2wks + CXR: patchy infiltrate, viral serology (+)
Chlamydophila pneumoniae
The most common cause of community-acquired
pneumonia (CAP) is
Streptococcus pneumoniae
Cause of rapid onset of high fever, cough, & sputum,
dyspnea; tachypnea in an elderly; CXR: lobar infiltrate; CBC: pronounced neutrophilic leukocytosis with left shift, is
Streptococcus pneumoniae
Gram-positive diplococci from sputum from a patient with lobar pneumonia yield a-hemolytic colonies and are confirmed by
Capsular swelling (Quelling rxn)
a-hemolytic colonies of Streptococcus pneumoniae is
differentiated from viridans streptococci definitively confirmed by
Optochin sensitivity
Population w/ .incidence of pneumococcal pneumonia is
AIDS
incidence of colonization of what organism is seen in very young and elderly, crowding, following viral URI (.PAF
receptors), fall/winter season?
Streptococcus pneumoniae
Streptococcus pneumoniae is transmitted P2P by
Respiratory droplets
Nasopharyngeal mucosal colonization is facilitated by
IgA protease
Streptococcus pneumoniae reaches lungs after
nasopharyngeal colonization via
aspiration
Major virulence factor, facilitating invasion and
dissemination of Streptococcus pneumoniae is
Polysaccharide capsule
Pneumococcal cell wall peptidoglycans, teichoic acid elicit
Inflammation
Lung cell injury in pneumococcal pneumonia is caused by
virulence factor?
Pneumolysin (a-hemolysin)
Multiple myeloma, C3 deficiency, asplenia - Hg SS, COPD,
diabetes, alcoholism, smokers are risk factors for mortality due to
pneumococcal pneumonia
Hematologic marker for poor prognosis of pneumococcal
pneumonia is
Leukopenia
Emipiric DOC of CAP in pts at risk or w/ comorbidity is
Azithromycin (or
levofloxacin) + ceftriaxone
Pneumonia due to highly penicillin-resistant Streptococcus
pneumoniae (Pen MIC >8) should receive
moxifloxacin or vancomycin
Mechanism of penicillin resistance in Streptococcus
pneumoniae is
PBP alteration by mutation
Pt w/ agammaglobulinemia or asplenia or sick-cell anemia
or decreased C3 should be vaccinated with
Pneumococcal polysaccharide
vaccine (PPSV: 23-valent)
Hx: a patient w/ serious CAD now on a ventilator, acquires
bronchopneumonia >72 hrs after hospitalization. TOW?
Pseudomonas aeruginosa
(VAP)
Cause of necrotizing pneumonia >72 hrs after
hospitalization of complicated viral illness
Staphylococcus aureus
(assume MRSA)
Patients that are aspiration prone have hx of
dysphagia, decreased
consciousness
Hx of a patient w/ seizure illness has fever, cough evolving
over 2-4 wks; CXR infiltrate (+).TOW?
Aspiration pneumonia
Community-acquired respiratory pathogens that cause
aspiration pneumonia
Streptococcus pneumoniae >
Anaerobes
Hospital-acquired respiratory pathogens that cause
aspiration pneumonia
Gram-negative bacilli > S.
aureus +/- anaerobes
Clinical Dx of sudden dyspnea +/- cyanosis, fever,
wheezing, often ARDS-like picture is
acid-related pneumonia
Bacterial etiology and Tx of aspiration pneumonia are
determined by
Gram stain (polymicrobic)
and culture of sputum
Empiric DOC of necrotizing pneumonia in a patient with
seizure illness
clindamycin + levofloxacin
Targeted Abx for anaerobic aspiration pneumonia is
clindamycin
Pneumonia in homeless/alcoholics; Gram-positive
diplococci in sputum Gram smear. TOW?
Streptococcus pneumoniae
Pneumonia in homeless/alcoholics; Gram-negative rods in
sputum smear. TOW?
Klebsiella pneumoniae
Cause of pulmonary embolism in a pt with IVDU
Staphylococcus aureus
Common cause of pneumonia in pts with CF
Pseudomonas aeruginosa
Sputum of a patient with hospital-acquired pneumonia
yields a Gram-negative rod that is oxidase (+). TOW?
Pseudomonas aeruginosa
Common cause of external otitis due to hot tub use is
Pseudomonas aeruginosa
A patient with diabetes has osteomyelitis after penetrating
foot injury. TOW?
Pseudomonas aeruginosa
The most widely used anti-pseudomonal penicillin
The most widely used anti-pseudomonal penicillin
The most widely used anti-pseudomonal aminoglycoside
Tobramicin > gentamicin
This pt >50 years, smoking hx, CMI. has pneumonia;
diarrhea, renal failure. Urine antigen (+) for pathogen. Pt responds
to azithromycin. TOW?
Legionella penumophila
Penicillin is ineffective against Legionnaire’s dz because
Intracellular organism
Individuals with defective CMI response has poor prognosis
of Legionnaire’s dz because
Intracellular organism
Asymptomatic patient with PPD (+)
Latent tuberculosis infection
(LTBI)
Cough > 2 wks, fever, night sweats, weight loss,
hemoptysis, SOB; CXR: upper lobe infiltrate. TOW?
Active Mycobacterium
tuberculosis infection
Oral drug regimen of choice for treatment of active TB
(aka: 1st line drugs) is
INH+RIF+PZA+EMB (oral)
+ Vit B6
Pyridoxine is added to 4-drug therapy for TB to prevent
neuropathy (due to INH)
Pt w/ TB fails to respond to 4-drug regimen w/ INH+RIF
resistance because
Multiply drug-resistant
(MDR) TB
Pt w/ MDR-TB fails to respond to INH +RIF+FQ+an
injectable drug (amikacin, capreomycin, or kanamycin) because
Extremely-drug resistant
(XDR) TB
Cause of TB-like Dz that does not respond to 1o TB Tx
regimen, in a pt. w/ AIDS
Mycobacterium avium –
intracellulare (aka: MAC)
Cause of chronic pneumonia in a patient with cancer,
receiving cytotoxic chemotherapy; lung-CT: halo/crescent sign (+)?
Aspergillus fumigatus
Hx of chronic pneumonia w/ lung bpsy histopathology (+)
for hyphae 2-4µm wide, septate, acute- angle branching. TOW?
Aspergillus fumigatus
Cause of TB-like LRI in a pt with outdoor activity (Giemsa
stain of bronchoscopy specimen: (+) for 2-5 µm yeasts) is
Histoplasma capsulatum
Pt with AIDS has blood culture (+) for histoplasmosis.
DOC has effects on
Ergosterol in fungal cell
membrane
TB-like Dz w/ ulcerative skin lesions. lung bpsy
histopathology (+) for large yeast w/ broad-based bud. DOC?
Intraconazole
Hx of acute onset of cough, fever, infiltrate in a black male
with CMI.; histopathology of lung (+) for a large sac of
endospores. DOC?
Fluconazole (indefinite)
Pt w/ aspiration pneumonia with cervico-facial lesion
should respond to
Penicillin G
Granular specimen from draining fistulae from a pt with
LRI on anaerobic culture should yield
Actinomyces israelii
Pt with AIDS or organ transplant has indolent pneumonia,
w/ or w/o CNS abscess or granuloma. TOW?
Nocardiosis
Organism w/ characterization of Gram-positive branching,
beaded, filamentous rod, weakly acid fast is
Nocardia asteroids
Hx of non-productive cough, fever and dyspnea evolving
over 2-4 wks. CXR (+): bilateral interstitial infiltrates, hypoxemia;
.LDH, CD4 count <200/mm3 in a MSM. TOW?
Pneumocystis pneumonia
DOC of pneumocystis pneumonia (PCP)
TMP-SMX
Pt has urinary urgency, frequency, dysuria; lab: pyuria (+)
or nitrite (+). TOW?
Cystitis due to E. coli
Significant UTI is confirmed by semiquantitative MSU
culture based on the threshold of
> 1,000 cfu/mL
Mode of acquisition of uropathogen is
Endogenous
Microbial (structure) factor favoring bacterial persistence
/colonization and UTI is
bacterial binding via fimbriae
Factor favoring bacterial persistence/colonization and UTI
despite high osmolarity and urea concentrations and low pH is
high bacterial growth rates
Host factor favoring bacterial persistence/colonization and
UTI is
Urinary stasis
Host factor favoring bacterial persistence/colonization and
UTI despite frequent voiding and high urinary flow is
Absence of bactericidal
effects of secreted proteins
Pyogenic inflammation in complicated UTI due to Gram-
negative bacteria is due to
Lipopolysaccharide (LPS)
Empiric DOC to treat community-acquired UTI in adults is
ciprofloxacin
The abx class that inhibits DNA gyrase or topoisomerase IV
and blocks with bacterial DNA replication is
Fluoroquinolones
DOC to treat UTI in pregnant women is
Nitrofurantoin
Gram-positive bacteria that cause uncomplicated UTI in
sexually active, young women are
Staphylococcus saprophyticus
Differentiation of Staphylococcus saprophyticus from S.
epidermidis (both coagulase negative) is based on
novobiocin resistance
In elderly or pt with risks of urinary stasis, fever, chills,
flank pain, and CVA tenderness; Lab: pyuria, casts, nitrite+. TOW?
Pyelonephritis due to E. coli
Pt hospitalized > 72 h for comorbidity has urinary
frequency, dysuria and foul-smelling urine; w/ flank pain, fever and
chills, in the presence of a urinary catheter:
Clue: GNR; fermenter; encapsulated; intrinsic ampicillin resistance)

Clue: GNR; slow fermenter; red pigment; intrinsic drug resistance)

Clue: GNR; swarming growth [very motile]; slow fermenter; intrinsic
drug resistance)

Clue: GNR; non fermenter; oxidase+, blue pigment; intrinsic drug
resistance)

Clue: GPC in chains; catalase-neg; grows in high salt; penicillin
resistance)
Klebsiella pneumoniae

Serretia marcescens

Proteus mirabilis



Pseudomonas aeruginosa

Enterococcus faecalis
If a patient with complicated UTI is severely ill or not
improving with therapy, do what rapid test next?
renal ultrasound (to rule out
urinary tract obstruction)
For a patient with complicated UTI, once culture and
sensitivity available, switch to what?
Narrow-spectrum abx
2 or more of the following: fever (T>38°C) or hypothermia
(T< 36°C), tachycardia (HR>90), tachypnea (RR>20), leukocytosis
(WBC>12,000 or differential w/ >10% bands). TOW?
SIRS
SIRS + infection (e.g., positive blood culture) is
sepsis
Sepsis + organ failure, decreased perfusion (lactic acidosis,
oliguria, altered mental status) or low BP. TOW?
Severe sepsis
Severe sepsis + hypotension despite fluids + lactic acidosis,
oliguria, altered mental status.
Septic shock
Septic shock due to Gram-negative bacteria (e.g., E. coli,
Klebsiella spp., or Pseudomonas aeruginosa) is
Endotoxic shock
Endotoxin that mounts pro-inflammatory cytokines,
responsible for endotoxic shock, is
Lipid A of LPS
Genital chancre begins as a papule, ulcerates to form a
single, painless, clean-based ulcer. TOW?
1o syphilis
Cause of genital chancre, begining as a papule, ulcerating to
form a single, painless, clean-based ulcer.
Treponema pallidum
A pen-allergy, non-pregnant, female pt w/ fever, "copper
penny" macular lesions on the palms or soles; RPR(+) should be treated with
Doxycycline
Management choice of tabes dorsalis (10-20yrs), iritis,
uveitis, or Argyll-Robertson pupils of pen-allergy in a pregnant
woman w/ pen allergy; RPR(+) is
Desensitization
Hx of painful clustered vesicles with an erythematous base;
urinary retention in a promiscuous woman. TOW?
HSV-2 >> 1
Giemsa stain of fluid from a herpetic lesion should reveal
Multinucleated giant cells
Patient with genital herpes does not respond to acyclovir
because pt is infected with
thymidine kinase deficient
HSV
A pregnant woman with 1o symptomatic HSV-2 infection is
at risk of her baby developing
neonatal (congenital) herpes
Cause of painful genital ulcers; purulent, grey base; painful
inguinal adenitis, in a man with multiple sexual partners is
Haemophilus ducreyi
Fastidious organism in the infiltrate of the penile ulcer, co-
localized with neutrophils and fibrin, in a pt w/ chancroid is
Haemophilus ducreyi
All sex partners of pt with chancroid, regardless of
symptoms, should be examined and treated with
Azythromycin > ceftriaxone
Most common cause of mucopurulent endocervical exudate
(Gram stain non revealing) in a sexually promiscuous woman
Chlamydia trachomatis D-K
Dx of mucopurulent urethral discharge, dysuria, penile
pruritis is based on
NAAT of urethral specimen
or urine (+)
DOC of most frequent cause of nongonococcal urethritis
Azythromycin > doxycycline
Cause of rare genital ulcers, inguinal lymphadenopathy
[cytology(-) for multi-nucleated giant cells; RPR (-)] in men is
Chlamydia trachomatis L1-L3
Hx of systemic Sx/Sn w/ cervical motion tenderness in a
woman with turbo-ovarian abscess. TOW?
PID
Cause of mucopurulent urethritis, dysuria, penile pruritis
[Smear (+):Gram-negative diplococci co-populated w/ PMNs] is
Neisseria gonorrhoeae
Deficiency in serum factors in a female pt w/ frequent
gonorrhea and DGIs is
C6-C9
Immune evasion of Neisseria gonorrhoeae in frequent mucosal infection is due to
Antigenic variation of pili.
Auxotrophic strains of N. gonorrhoeae with serum
(complements) resistance are likely to cause
Septic arthritis (aka: DGI)
Most frequent complication of gonococcal (GC) infection in
men
Epididymitis
Cause of "bull headed clap", urethral stricture, prostatitis is
Neisseria gonorrhoeae
Urethritis is treated with ceftriaxone + azythromycin
because
Urethritis is treated with ceftriaxone + azythromycin
because
An older woman with PID and tubo-ovarian abscess
receives ceftriaxone, azythromycin, and metronidazole because
Polymicrobic (endogenous)
infection
Cause of anogenital warts w/ histology (+): koilocytes is
HPV 6 and 11
Cause of atypical squamous cells of undetermined
significance (ASCUS) on pap smear w/ no clinical signs of
infection is
HPV 16 and 18
Cause of koilocytotic cells and possible progression to
squamous cell carcinoma
HPV 16 and 18
Next step to identify viral cause of ASCUS on pap smear w/
and further management in a woman of age > 29 years is
Colposcopy > HPV DNA in
bpsy
Wet prep of vaginal discharge from a pt w/ vaginal pruritis;
ectocervical erythema ("strawberry cervix") should reveal
motile tissue flagellate
Gram stain of vaginal discharge w/ fishy odor from a pt w/
vaginal pruritis but no erythema and normal cervix should reveal
SECs stippled with Gram-
variable organisms.
Pathology of bacterial vagisnosis is overgrowth (in vagina)
of anaerobic Mobiluncus species and
Gardnerella vaginalis
DOC of bacterial vaginosis is
metronidazole
Wet prep of curdy discharge (no odor), adhering to vaginal
walls, from a pregnant woman w/ recent UTI, who now has severe
vaginal pruritis; vulvovaginal area - erythematous should reveal
budding yeasts with
pseudohyphae
Normal commensal of skin, GI & GU tracts; endogenous
overgrowth of budding yeast, capable of >10 diseases. TOW?
Candida albicans
Mechanism of action of a po DOC of vulvovaginal
candidiasis is
blocks C14a-lanosterol
demethylase
Hx of flu-like illness, lymphadenopathy, maculopapular
rash in a bisexual man. Lab: lymphopenia and transaminase
elevations; monospot/all serology (-). TOW?
Acute retroviral syndrome
Time from infection (acquisition) to acute seroconversion detected by HIV serology (ELISA/ WBlot) is
6-12 weeks.
Hx of mononucleosis-like illness and lymphadenopathy in a
man who has sex man. Serology (-). What is HIV viral load?
>10,000 copies/ml
Host-cell receptor for HIV-1 infection
CD4
Homozygous for deletions in what gene renders resistance
to infection and some protection against progression.
CCR5
Host cells that trap HIV and mediate the efficient
transinfection of CD4+ T cells are
Dendritic cells
A man, who practices “sex with another man”, has
antibodies to HIV (ELISA and WB) but asymptomatic. TOW?
Clinical latency
What happens to HIV-1 virus when acute retroviral
syndrome progresses to clinical latency?
Virus continues to replicate
low level.
A man who practices “sex with another man”, is now HIV-1
serology (+) and has dual symptomatic infections/cancer (any two
from below). Expected CD4+ count is
i. Candidiasis, esophageal, bronchi, trachea, or lungs
ii. Cervical cancer, invasive
iii. Coccidioidomycosis, extrapulmonary
iv. Cryptococcosis, extrapulmonary
v. Cryptosporidiosis, chronic intestinal
vi. Cytomegalovirus retinitis (with vision loss)
vii. Encephalopathy, HIV-related
viii. Herpes simplex - Chronic ulcers
ix. Histoplasmosis, disseminated or extrapulmonary
x. Isosporiasis, chronic intestinal (duration >1 mo)
xi. Kaposi sarcoma
xii. Lymphoma, Burkitt
xiii. Lymphoma, primary, of the brain
xiv. Mycobacterium avium complex or Mycobacterium
kansasii infection, extrapulmonary
xv. Mycobacterium tuberculosis infection, any site
(pulmonary or extrapulmonary)
xvi. Pneumocystis pneumonia
xvii. Progressive multifocal leukoencephalopathy
xviii. Wasting syndrome due to HIV infection
CD4+ < 200/µL
A man with HIV infection has chronic diarrhea, oral thrush
+ toxoplasma encephalitis. Most likely CD4+ count is
< 50 cells/µL.
Most common cause of HIV- associated peripheral skin or
mucosal ulcers
HSV-1 (>> Histo > CMV >
VZV > Syphilis)
Most common cause of HIV- associated nodules (neoplasia)?
HHV-8 (aka KSHV)
Hx of fatigue, nausea, abdominal pain, diarrhea, fever,
chills, night sweats, dry persistent cough w/ SOB and weight loss in
a man with AIDS. Lab: PPD (-); blood culture (+) for AFB. TOW?
Mycobacterium avium-
intracellulare (MAI) complex
(aka: MAC)
Common cause of retinitis, viral pneumonitis or esophagitis
in AIDS
CMV
Cases of CMV disease occur with immunosuppression level
CD4< 50
cytopathology of CMV infected tissue is characterized by
large cells with
nuclear (Cowdry owl’s eye)
and cytoplasmic inclusions
Hx of progressive CNS dz in a pt w/ AIDS: hemiparesis,
visual, ataxia, aphasia, cranial nerves, sensory. Head MRI: ring-
enhancing lesions. Toxo antibody (-). TOW?
JC virus
Definitive indication for initial HAART is CD4+ count?
350/mm3.
Objective of ARV Tx is to reduce viremia to what level of
genomic RNA/mL
< 50 copies RNA/mL.
Initial regimen of anti-retroviral therapy is
Emtricitabine + Tenofovir +
Efavirenz
Abacavir, emtricitabine, lamivudine, zidovudine, tenofovir
belong to what class of antiretrovirals?
NRTIs
Efavirenz, nevirapine belong to what class of
antiretrovirals?
NNRTIs
Atazanavir, Lopinavir, Saquinavir belong to what class of
antiretrovirals?
Protease inhibitors
This drug binds to gp41 and prevents conformational
change required for viral fusion and entry into cells.
enfuvirtide
This drug inhibits integrase, responsible for insertion of
HIV proviral DNA into the host genome.
raltegravir
A man has AIDS and CD4 <200cells/µL or thrush.
Antibacterial prophylaxis needed besides HAART is
TMP-SMX (for PCP)
A man has AIDS and CD4 <100 + pos toxo IgG.
Chemoprophylaxis needed besides HAART is
TMP-SMX (for Toxoplasma
encephalitis)
A man has AIDS and CD4 <100 + PPD >5mm induration.
Antibacterial prophylaxis needed besides HAART is
INH + pyridoxine
A man has AIDS and CD4 <50. Antibacterial prophylaxis
needed besides HAART is
azithromycin (for MAC)
Hx of fever, a pustule at a cat scratch site, adenopathy,
hepatosplenomegaly in a pt w/ AIDS. Warthin-Starry stain tissue
(+). TOW (clue: bacillary angiomatosis)?
Bartonella henselae
Leading causes of congenital infections are
ToRCH3eS-List

To = Toxoplasma gondii




R = Rubella

C = CMV

H = HSV-2

H = HIV

H = HBV

S = Syphilis

List = Listeria monocytogenes
Cause of severe CNS sequelae, chorioretinitis, systemic
disease in a neonate (mom at pregnancy had mono-like illness after
eating undercooked beef or pork or exposure to oöcysts in cat
feces) is
Toxoplasma gondii
Drug for pregnant woman in first trimester to prevent
transmission if mother seroconverts is
Spiramycin
Hx of deafness, cataracts, heart defects, or microcephaly in
a child (of a seronegative, caregiver mom, exposed to “Blueberry
muffin baby” in 1st trimester). TOW?
congenital rubella syndrome
(CRS)
Dx of CRS usually with positive anti-rubella antibody type?
IgM
Microcephaly, seizures, sensorineural hearing loss, feeding
difficulties, petechial rash, hepatosplenomegaly, or jaundice in a
neonate. PCR of any body fluid should yield
CMV
After primary infection, CMV, characterized as enveloped
dsDNA betaherpesvirus; establishes
lifelong latency
Hepatosplenomegaly, neurologic abnormalities, frequent
infections in a neonate w/ low CD4+ counts. Woman before
birthing should have received
Nevirapine
Cause of vesicular skin lesions + conjunctivitis in a child
(asymptomatic at birth)
HSV-2
Hx of cutaneous lesions, hepatosplenomegaly, jaundice,
saddle nose, and saber shins. Hutchinson teeth, + CN VIII deafness
in a neonate (mom is a prostitute). TOW?
3o syphilis
Neonatal septicemia or meningitis (mom had flu-like Sx and
ate imported cheese during pregnancy). TOW?
Listeria monocytogenes
What are the SIX red rashes of childhood (acute, febrile
exanthema illnesses)?


(Clue1: maculopapular rash; off-white lesions on buccal mucosa,
MMRV vaccine prevents)

(Clue2: maculopapular rash starting on face moving to foot; MMRV
prevents)

(Clue3: scarlatina rash post pharyngitis)

(Clue4: vesicular rash, moderate pain)

(Clue5: maculopapular “slapped face” appearance in a young child)

(Clue6: maculopapular rash and systemic Dz in immunocompromised
pt)
Measles



Rubella



Scarlet fever (GAS)

Chicken pox (VZV)

Parvovirus B19

HHV-6
Worldwide rubella infection, with only human reservoirs
known this infectious agent is a
RNA togavirus
>95% seropositive after MMRV if >12mos age and lifelong
protection against rubella is conferred with?
Single dose
Cause of single or multiple scaly and/or crusted patches
and/or plaques, affecting the scalp or beard area +/- inflammation.
Dermatophytes
KOH prep of scales from the scalp and plucked hairs from
cutaneous mycoses may reveal?
hyphae and spores
Most common cause of cutaneous mycoses
Trichophyton spp.
Common cause of cutaneous mycosis with animal contact
Microsporum spp.
Oral DOC of cutaneous mycoses
itraconazole
Topical DOC of cutaneous mycoses
terbinafine
Dz w/ subcutaenous lesions w/ slow spread by lymphatic
system producing nodules in a gardener, or from rose-thorn injury.
Sporotrichosis
Cause of subcutaenous lesions w/ slow spread by lymphatic
system producing nodules in a gardener, or from rose-thorn injury.
Sporothrix schenckii
Dimorphic fungus that grows at 37°C as cigar-shaped yeast,
and produces septate hyphae and conidia (in daisy arrangement) at
25°C is
Sporothrix schenckii
DOC of sporotrchosis
itraconazole.
Cause of deeper and wider lesions with interconnecting
subcutaneous abscesses arising from infection of several
neighboring hair follicles, in young children.
Staphylococcus aureus
(Curbuncle)
Cause of superficial pustules progressing to erosions
covered by honey-colored crusts, surrounded by erythematous halo,
in young children.
Staphylococcus aureus >>
Streptococcus pyogenes (non-
bullous impetigo)
Dz characterized by bullae and denuded areas after the
blisters rupture, covered by thin, varnish-like light brown crusts;
regional lymphadenopathy, in children.

DOC if lab: gram stain and culture of pus or base of the lesions yields
GPC in chains.

DOC if lab: gram stain and culture of pus or base of the lesions yields
GPC in clusters.
Bullous impetigo

Penicillin G

Nafcillin
mecA (SCC) genes which encode PBP2a, w/ low affinity for
ß-lactams; confers resistance in Staphylococcus aureus against
what?
Nafcillin
Cause of spreading (butterfly-wing) erythema on the face
that responds to empirical penicillin.
Streptococcus pyogenes
(Erysipelas)
Cause of severe pain on his knee w/ site of injury is tender
and erythematous. Blood culture may yield?
Streptococcus pyogenes.
(Cellulitis)
What is the microbial factor that promotes degradation of
C3b by binding to factor H, the serum ß globulin factor
M protein
Other epidemiologically linked or risk-associated causes of
cellulitis are:


Clue1: cat/dog bite. What?



Clue2: Salt water exposure. What?

Clue3: Fresh water exposure. What?

Clue4: Neutropenia. What?

Clue5: Human bite. What?
Pasteurella multocida /
Capnocytophaga canimorous

Vibrio vulnificus

Aeromonas hydrophila

Pseudomonas aeruginosa

Eikenella corrodens
Most likely cause of fever/chills/ night sweats, localizing
pain/tenderness or swelling/erythema (lab: .ESR, .CRP; .WBC w/
left shift. Radiology: periosteal elevation.) is
Staphylococcus aureus
(Osteomyelitis)
Major antiphagocytic virulence factor of drug-resistant
organism that causes osteomyelitis is
protein A
Major neutrophil-damaging virulence factor of drug-
resistant organism that causes osteomyelitis is
Penton-Valentine leukocydin
Cause of vertebral, sternoclavicular or pelvic bone
infections (in pt w/ IVDU) or osteochondritis of foot (following
penetrating injuries through tennis shoes)?
Pseudomonas aeruginosa
Cause of osteomyelitis in pt w/ underlying sickle cell Dz;
blood culture +)?
Salmonella typhimurium
Cause of chronic, vertebral osteomyelitis (blood culture
negative)?
Mycobacterium tuberculosis
Cause of osteomyelitis in pt. w/ hx of cat bites; GNSR;
fastidious growth of wound culture?
Pasteurella multocida
Cause of fever, chills, malaise, joint pain, swelling. PE:
tenderness, erythema, heat, swelling, decreased ROM. CBC:
leukocytosis w/ neutrophils predominating; joint aspirate: no
crystals.


Clue1: sexually active; BLCx (-); responds to ceftriaxone

Think of other pathogens (BLCx negative):

Clue2: Rheumatoid arthritis?

Clue3: IVDU?

Clue4: Unpasteurized dairy products

Clue5: Diabetes
Septic arthritis

Neisseria gonorrhoeae

S. aureus

S. aureus, P. aeruginosa

Brucella spp.

S. agalactiae (GBS)
Dz is characterized by arthritis in up to 6 joints (especially
knees, feet), low back pain/stiffness, irritable eyes w/ or w/o
redness, conjunctivitis, iritis, malaise. TOW?


Caused by:

Clue1: sexually acquired



Clue2: non-sexually acquired

Reactive arthritis
C. trachomatis, N.
gonorrhoeae

Campylobacter, Salmonella
Cause of bacteremia in neutopenic pts with central line or
pts with prosthetic devices and catheters; blood culture (+)
Staphylococcus epidermidis
Cause of intraabdominal abscess w/ putrid pus; anaerobic
bacteremia in pt with trauma or solid GI tumor?
Bacteroides fragilis.
A woman with obstetric infection has fever > 102oF, SBP <
90; diffuse sunburn-like rash or desquamation of palms and soles;
multisystem Sx/Sns; vomiting, and diarrhea; BLCx (-). TOW?
Staphylococcal Toxic shock
Syndrome
What is the toxin associated with staphylococcal toxic
shock syndrome?
TSST-1 (a superantigen)
Cause of severe, watery diarrhea in a woman with toxic
shock syndrome?
Enterotoxin (coregulated with
TSST-1)
Cause of toxic shock syndrome, which responds to
vancomycin and clindamycin?
MRSA
Hx of fever > 38.9oC, SBP < 90 ; diffuse sunburn-like rash
or desquamation of palms and soles, in a man w/ necrotizing
fasciitis or myositis; multisystem involvement; BLCx (+). TOW?
Streptococcal toxic shock
syndrome
What is the toxin associated with streptococcal toxic shock
syndrome?
SpeA (superantigen)
DOC for streptococcal toxic shock syndrome
PenG + clindamycin
Hx of fever, chills, and hypotension. Blood culture yields a
GNR, oxidase (-), lactose fermenting organism on MacConkey
agar. Immunological mediators of sepsis.
IL-1 and TNF
DOC for a neutropenic pt w/ line-associated infection w/
immune suppression (hematologic malignancy, organ or
hematopoietic stem cell transplantation, chemotherapy); w/ positive
blood cultures and ß-D-glucan antigenemia?
Caspofungin
DOC for a line-associated infection in a pt w/ GI tumor; lab:
positive blood cultures and ß-D-glucan antigenemia?
Fluconazole
Without prophylaxis with valganciclovir, D+/R- solid organ txp pts will develop
CMV disease
Cause of mononucleosis-like dz with fever, myalgia/
arthralgia w/ lab: leukopenia, LFT abnls, in a pt w/ solid organ
transplant?
CMV
Lung biopsy reveals large cells with nuclear inclusions
(Cowdry owl's eyes inclusion bodies) in a pt with AIDS and
interstitial pneumonia. TOW?
CMV
DOC for CMV antigenemia in a febrile pt with solid organ
tansplant?
valganciclovir
Cause of hematuria, hemorrhagic cystitis, or ureteric
stenosis, or interstitial nephritis in a severly immunocompromised
pt?
BK virus
What is the most common cause of bacteremia associated
w/ foreign device (prostheses, intravenous cathether, or central
lines) in co-morbid, hospitalized pts?
Staphylococcus epidermidis
What is the cause of infections associated w/ ventilator
support of respiration in co-morbid pts in the ICU?
Pseudomonas aeruginosa
DOC for a pt w/ travel hx (back from the tropics), who has
flu-like symptoms; splenomegaly; lab: CBC: anemia,
thrombocytopenia, hypoglycemia. Blood smear: enlarged RBCs
and Schuffner dots.
mefloquine + primaquine
Which drug is contraindicated in specific Tx of liver form
of malaria in pts w/ G6PD deficiency?
Primaquine
DOC for a pt w/ travel hx (back from the tropics), who has
flu-like symptoms (fever > 103oF), seizure, hyperparasitemia
(>2.5% of RBC), pulmonary edema, or renal failure, or severe
anemia?
Quinidine and doxycycline.
Cause of malaria-like illness in an immunosuppressed pt
w/o travel hx; lab: blood smear has cross-over rings in the RBCs?
Babesia spp.
A pt from S. America has a week-long fever, anorexia,
lymphadenopathy, mild hepatosplenomegaly, and myocarditis; a
nodular lesion on the arm. Blood smear should reveal motile
species of what?
Trypanosoma cruzi
Cause of a chronic-stage systemic dz w/ cardiomyopathy, megaesophagus, megacolon, and weight loss in a pt from S.
America, who does not respond to nifurtimox.
Trypanosoma cruzi
Cause of protracted fever and Crohn’s, celiac dz, ocular
problems, and lymphadenopathy; duodenal biopsy demonstrating
foamy macrophages in lamina propria?
Tropheryma whipplei
Clinical Dx of painless papule (on arms, face, or chest),
then vesicles/bullae, then black eschar + edema evolving over 3-5d
associated with animal exposure is
Cutaeneous anthrax
Cutaneous anthrax can be treated in 7-10 days with
Ciprofloxacin
Animal exposure or biowarfare-associated fever, chills,
sweats, GI sx, cough, malaise, chest pain, but no coryza (first 3-4d);
then sepsis; CXR: wide mediastinum and bloody pleural effusion.
Blood culture should yield
Bacillus anthracis
Inhalation anthrax is treated with
Fluoroquinolone >
doxycycline
Need to treat inhalation anthrax 60-100 days because
Spores persist in vivo 30 days
PxPr to prevent inhalation anthrax via aerosolized spores
from powder particle size < 10 microns requires
Cipro for 60 days
Species of Clostridium that causes afebrile, systemic toxic
diseases in infants (honey), and in adults foodborne (meat, canned
vegetables), wound (injected), iatrogenic (cosmetic) is
C. botulinum
Many pts w/ flaccid paralysis; unusual Clostrium botulium
types (not A, B or E), common geography without common food
source are clues to
bioterrorism
Aerobic small slender gram-negative rod, erroneously
identified as Pseudomonas sp., which causes glanders in
horses and rarely humans; may be used in bioterrorism is
Burkholderia mallei
Small, pleomorphic, aerobic Gram-neg rod that causes
pathophysiology: 1) bite/abrasion (acquired from tick exposure
or contact with rabbits) . nodule/ulcer . node . sepsis, or
2) inhalation (bioterrorism) . acute fever, dry cough. CXR:
infiltrates + hilar adenopathy, is
Francisella turlarensis
Hx of acute fever, myalgias, remorrhagic rash,
conjunctivitis, pharyngitis, headache, diarrhea, and
thrombocytopenia in bioterrorism indicates
Viral hemorrhagic fever (e.g.,
Marburg, Ebola)
Aerobic, Gram-neg bipolar rod, which causes
pathophysiology of (a) painful lymphadenitis, fever, chills,
headache (after exposure to rodents, rabbits or fleas) (b) sepsis;
(c) pneumonic (post bubo or epidemic): severe, often with
hemoptysis and dyspnea, is
Yersinia pestis
Hx of sudden fever = 39°C , homogeneous vesiculo-
pustular rash (unlike common viral exanthems) in multiple pts
is caused by
Variolla major virus (small
pox)
Hx: fever, headache, neck stiffness, and altered mental
status; Kernig's/Brudzinski's sign other focal neurologic findings,
rash, headache, seizures + myalgia; CSF: WBC > 2000 or PMNs >
1200; glucose < 34, protein > 220


CSF gram stain of the most likely pathogen of ABM in a 6 mos-6yr old
(or adults > 50 years) should reveal

CSF gram stain of the most likely pathogen of ABM in an older child
or young adult should reveal
Acute bacterial meningitis
(ABM)


Gram-positive diplococci

Gram-negative diplococci
Most common cause of sepsis/meningitis in
newborns/neonates?
Streptococcus agalactiae
Cause of fever, headache, photophobia, nausea/vomiting,
rash, diarrhea, meningeal signs, in older children in the summer
months; CSF with 10-<1,000 WBC typical, mostly monos,
moderately elevated protein?
Aseptic meningitis caused by
enteroviruses
Cause of aseptic meningitis in men with exposure to
rodents?
Leptospira interrogans
Cause of aseptic meningitis with hx of tick bite and
erythema migrans?
Borrelia burgdorferi
Cause of aseptic meningitis with hx of sex with multiple
partners; CSF PCR(+)?
HSV-2 > 1
Cause of fever, headache, photophobia, meningismus, in pts
w/ solid organ transplant, malignancy, corticosteroid use. CSF glucose < 2/3 serum glucose, elevated protein, WBC > 5 with
PMNs?
Listeria monocyotgenes
How does Listeria monocytogenes differ from other ß-
hemolytic bacteria?
Gram-positive rods; tumbling
motility
Cause of chronic meningoencephalitis in a pt, who uses
infliximab or native from endemic region; PE: papilledema. CXR
(+). Lab: elevated monocytes on differential, low CSF glucose?
Mycobacterium tuberculosis
Test to confirm subacute mengoencephalitis in a,
immunocompromised pt (CD4 <100); vesicular skin lesions [CSF
profile: protein 30-150mg/dl, monos 10-100]?
CSF India ink
Cause of meningoencephalitis after a hx of respiratory
illness after travel to SW USA?
Coccidioides immitis
Test to confirm CNS pathology with fever, cognitive
deficits, focal neurologic signs, seizures; temporal lobe
involvement on MRI. Lab: no papilledema, CT (no brain lesion)?
CSF PCR (+)
Cause of fever, cognitive deficits, focal neurologic signs,
seizures, abnormal mental status with ataxia, hemi-paresis, in a pt
w/ AIDS?
JC virus > HHV-6
Cause of fever, cognitive deficits, focal neurologic signs,
seizures or abnormal mental status with ataxia in an adult during
outdoor activity?
West-Nile virus > SLE
Hx of fever, cognitive deficits, focal neurologic signs,
seizures, in a pt w/ AIDS (CD4 < 50). MRI: multifocal (ring-
enhancing) lesions in basal ganglia. Rule out?
Toxoplasma encephalitis (TE)
HIV-infected Pt with TE should receive (for life)
pyrimethamine + leucovorin +
sulfadiazine
Folinic acid (leucovorin) prevents bone marrow suppressive
effect of
pyrimethamine.
Cause of confusion, stiff neck, irritability over wks to
months, in immunocompromised pts; CT/MRI = multifocal lesions
in midbrain, brain stem, & cerebellum; wet mount CSF = motile
macrophage-like organisms
Acanthamoeba spp. (GAE)
Cause of severe headache and other meningeal signs, fever,
vomiting, and focal neurologic deficits, frequently progressing to
coma, in a healthy boy (summer diving activity)?
Naegleria fowleri (PAM)
Cause of seizures, chronic headache, symptomatic
hydrocephalus, in immigrants; pt. successfully responds to praziquantel + anti-convulsant drug?
Taenia solium
(neurocysticercosis)
Pt from Africa had fever, lymphadenopathy, chancre, and
pruritus weeks ago; now has headaches, somnolence, neuro Sns;
slowly responds to pentamidine isothionate or suramin. TOW?
Sleeping sickness caused by
Trypanosoma brucei
Hx of rigidity, muscle spasm, and autonomic dysfunction.
Trismus due to masseter spasm in an infant w/ umbilical stump
infection. Neurotoxin interferes w/
GABA and glycine
Hx of afebrile illness w/ diplopia, dysarthria, dysphoria,
dysphagia, in a pt w/ IDU skin poppers with black tar heroin.
Neurotoxin blocks the release of
Acetylcholine
Immediate treatment of a male infant w/ constipation, a
weak cry, and drooling, hypotonea and cranial neuropathy, after
ingestion of home-processed honey.
Equine immune globulin
(infant botulism)
Ingestion of a raw potato delivers a new vaccine protein to
elicit an immune response. The immune structure to interact with
the vaccine protein?
Lamina propria mucosae
Inflammation and the resulting increase in vascular
permeability permit leakage into damaged or infected sites are
effected by
Phagocytic cells and acute
phase proteins
The serum of a pt, who has IgG and IgM deficiency,
appears to fix complement in an assay for tetanus antibodies. What
is the explanation?
Activation of the alternate
pathway
A 3-year-old boy with genetic C3 deficiency has recurrent
ear and lung infections due to pyogenic bacteria. Deficiency of
what?
B lymphocytes
A very young child, w/ recurrent infections due to
Staphylococcus aureus, now has numerous granulomas. TOW?
Chronic granulomatous dz
Treatment with which protease enzyme causes decrease in
avidity of IgG w/o changing the specificity of the antibody?
Papain
Cells activated by both .-IFN and CD40 are
Macrophages
High-dose chemo has caused severe bone marrow
suppression in a pt with hematologic malignancy. Reversal is
plausible with what?
GCSF
Function of the T-lymphocyte receptor (CD3) complex of
transmembrane proteins?
Signal transduction
The MHC class I pathway presents an antigen directly to
what?
CD8+ T lymphocytes
HSV infection can block the transfer of antigenic peptides
from the cytoplasm to the ER of the infected cells. As a result of this, action of what cell type is compromised?
CD8+ T cells
Infection of the thyroid gland can induce the expression of
MHC II molecules. Which cell types would initiate an autoimmune
response, leading to Hashimoto’s thyroiditis?
CD4+ T cells.
PPD skin test (+) in a pt , who was vaccinated against
turberculosis in his native country, reflects response of what cell
type?
CD4+ T lymphocytes (Th1
response . .-IFN)
A man with hx of MI is given a morphine injection for a
new episode of chest pain; 10 mins later, he has itching and
urticaria. Mechanism of this reaction?
mediators from sensitized
mast cells
Loss of skin pigments, sense of touch, inability to feel
objects and pain in a pt from Africa, whose skin scraping contains
AFBs, is caused by
Th1-mediated DTH reactions
A man with polycystic kidney dz, who receives a renal
transplant and cyclosporine, develops a high temp and swelling and
tenderness in the grafted kidney. TOW?
Immunity to the donor MHC
antigens.
A man who now has progressive stupor and laryngeal
spasms for 3 days after pt was being attacked by a wild bat in a
cave a month ago should have received
Inactivated rabies virus
vaccine
Alternative and lectin pathways of complements activated
bacterial surfaces
Classic complement pathway is activated by antibody-
antigen complexes involving antibody class type
IgM >> IgG
Chemotactic and anaphylotoxic complements are
C3a, C5a
successful opsonization of all non-encapsulated bacteria are
by complement
C3b
Defect or deficiency of which complements predisposes
individuals to infections caused by Neisseria spp., the causative
agents of gonorrhea and meningitis
C6-C9
Antimicrobial (immune) response important for intracellular
bacterial infections involves cell type
Th1 CD4 T cells
Immune response important for viral infections involves
cell type
CD8 cytolytic T cells
Major antibody in secretions and plays a significant role in
first-line defense at the mucosal level is
IgA
Main antibody in the initial “primary” immune response and
allows good complement activation is
IgM
Fc region of this immunoglobulin binds to eosinophils,
basophils and mast cells and is significant mediator of allergic
(hypersensitivity) reactions
IgE
What on macrophages enables them to sense that the
material is microbial in origin, and must therefore be eliminated
quickly?
Toll-like receptor
These oxygen-dependent enzymes: NADPH oxidase,
superoxide dismutase, and myeloperoxidase are involved in killing
of what?
Gram-positive bacteria
These oxygen-independent enzymes/proteins: lysosome,
lactoferrin, defensins and other cationic proteins are involved in
killing of what?
Gram-negative bacteria
Infections persist, because m. activation is defective,
leading to chronic stimulation of CD4+ T cells in what dz?
Chronic granulomatous Dz
Defective respiratory burst, predisposing chronic bacterial
infection is associated with deficiency of what?
Glucose-6-phosphate
dehydrogenase (G6PD)
All nucleated cells express MHC I antigens
HLA-A, B, C
Antigen-presenting cells express MHC II antigens
HLA-DP, DQ, DR
Lymphocyte proliferation (T, B) and NK . cytotoxicity are
undertaken by what cytokine?
IL-2
B-cell activation, IgE and IgG4 switch, . TH1 cells/ Mf, .
IFN-., TH0 . TH2 are all undertaken by what cytokine?
IL-4
Mf activation; elevated expression of MHC and FcRs
molecules on B cells, IgG2 class switching, increased IL-4 and
TH2 are all undertaken by what cytokine?
IFN.
The Th1 response, driven primarily by IFN-. leads to the
activation of
macrophages
The Th2 response, driven primarily by IL-4 and IL-5, leads
to the production of IgE and IgG4 and to the activation of
mast cells and eosinophils.
Variable T and B cells in DiGeroge’s syndrome is
associated with
Thymic aplasia
No B cells and immunoglobulins in X-linked
agammaglobulinemia (Bruton’s) is associated with
Loss of Btk tyrosine kinase
Lack of anti-polysaccharide antibody and impaired T-cell
activation causing Wiskott-Aldrich syndrome is associated with
X-linked-defective WASP
gene
Inability to control B cell growth in X-linked lympho-
proliferative syndrome is associated with
SH2D1A mutant
Glomerulonephritis, pulmonary hemorrhage in
Goodpasture’s syndrome is caused by what autoantigen?
basement membrane collagen
type IV
Hyperthyroidism in Grave’s Dz is caused by what
autoantigen?
Thyroid-stimulating hormone
Progressive muscle weakness in Myasthenia gravis is
caused by what autoantigen?
Acetyl choline receptor
Brain degeneration, paralysis in Multiple sclerosis (MS) is
caused by what autoantigen?
Myelin basic protein,
proteolipid protein
Localized allergies (e.g., drug allergy, asthma, hay fever)
and anaphylaxis (food, drug) w/ systemic inflammation throughout
circulation are associated with reaction?
Type I hypersensitivity
Autoimmune hemolytic anemia: Ab’s produced vs RBC
membrane Ag’s, mismatched blood (transfusion rxn), and allergies
to antibiotics (e.g., penicillins, sulfa drugs) are associated with
reaction?
Type II hypersensitivity
Grave’s Disease, Myasthenia Gravis, Goodpasture’s
syndrome are all associated with reaction?
Type II hypersensitivity
Post-streptococcal glomerulonephritis, serum sickness to
horse diphtheria anti-toxin, systemic lupus erythematosis (SLE),
and rheumatoid arthritis are all associated with reaction?
Type III hypersensitivity
Poison ivy, erythematous induration in tuberculin skin test,
and transplantation/graft rejection are all associated with reaction?
Type IV hypersensitivity