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30 Cards in this Set

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Group A streptococcus

lab characteristics

pathogenesis
Streptococcus Pyogenes
gram positive cocci in chains
beta hemolytic (clear) inhibited by Bacitracin, PYR +

Pathogenesis: Hyaluronic acid capsule--non-immunogenic; inhibits phagocytic uptake
M-protein-antiphagocytic

Toxins: (lysins)
Streptolysin O--immunogenic (rheumatic fever)
Streptolysin S--nonimmunogenic

streptokinase--breaks fibrin, helps spreading
streptococcal DNAse--liquifies pus, extension of lesion
Hyaluronidase--hydrolyses the ground substances of the connective tissues (spread of cellulitis)

Exotoxins A-C (pyrogenic or erythrogenic exotoxins)
Group A streptococcus

diseases

treatment
Suppurative Strep Pyogenes Infections:
1. Pharyngitis
2. Scarlet fever--blanching "sandpaper rash", strawberry tongue, nausea/vomiting
3. Pyoderma/Impetigo--pus producing skin infection (honey crusted lesions)
4. Erysipelas--"slapped cheek (does not blanch, no raised corners)
5. Necrotizing faciiatis (cellulitis--blanches, flat)

Non-suppurative
1. Rheumatic fever--sequelae to pharyngitis w/ group A strep--antibodies to heart tissue (~19 days) fever,joint inflammation, carditis, erythema nodosum
2. Acute glomerulonephritis (M12 serotype)--sequelae to pharyngitis or cutaneous --immune complexes bound to glomeruli/pulmonary edema and hypertension, dark urine

treatment:
beta-lactam antibiotics or erythromycin
Group B streptococcus
labs

diseases

treatment
Streptococcus Agalactiae
gram positive cocci in chains
beta hemolytic (same as group A)

Bacitracin Resistant!
hydrolyze hippurate, cAMP test positive

found in vagina(15-20%)-- newborn infected during birth
--causes neonatal septicemia and meningitis

treatment: Ampicillin w/ cefotaxime or gentamicin
Streptoccus pneumoniae

laboratory characteristics
"pneumococcus"

Alpha hemolytic (partial--green)
Inhibited by optochin

gram positive lancet shaped diplococci

lysed in bile (unlike Streptococcus Viridans)
Streptoccus pneumoniae

Pathogenesis
IgA--helps colonization
Techoic Acids--attachment
Polysaccharide capsule--inhibits phagocytosis (via alternative complement path-antibody independent)
Quellung reaction positive

Pneumolysin O--damages respiratory epithelium--"rusty sputum"-RBC's & WBC's

Peptidoglycan/techoic acids-- highly inflammatory in CNS
Streptococcus Pneumonia

Diseases

Treatment
Bacterial Pneumonia--most common bacterial cause (shaking chill, high fever, lobar consolidation w/ blood tinged "rusty" sputum)

Adult meningitis (most common cause) CSF high WBC, low glucose

Otitis Media & Sinusitis(kids)
most common cause

Treatment: Penicillin G (resistant strains--Vancomycin +/- Rifampin)

prevention--vaccine(23 serotypes of capsule)
Viridans Streptococci

labs & reservoir
S. Salivarius
S. Mutans
S. Sanguis

Alpha Hemolytic
Optochin resistant(unlike S.Pneumonia)
Also-not bile soluble

Reservoir: human oropharynx (normal flora)
Viridans Streptococci

pathogenesis
diseases
treatment
Pathogenesis:
Dextran(biofilm) mediated adherence onto tooth enemal or damaged heart valve/hole

Diseases: dental caries
infective endocarditis

Treatment: Penicillin G w/ aminoglycoside for endocarditis (PCN prophylaxis if damaged valves)
Enterococcus Feacalis
= Streptococcus Feacalis (group D)
Gamma hemolytic (no hemolysis)
Gram positive cocci in chains
Catalase negative
Bile esculing + (black)allows survival in bowel/gall bladder

Reservoir: human colon, urethra, genital tract

Diseases: urinary/biliary infections, subacute infective endocarditis, infections after GI/GU procedures

Tx: Vancomycin IV, most strains have some drug resistance
Staphylococcus Aureus

labs & distiguishing characteristics

reservoir
Catalase positive (unlike strep)
Beta-hemolytic
gram positive cocci clusters

coagulase positive (unlike S. epidermis & saphrophyticus)

Salt tolerant, ferments mannitol

Reservoir: normal flora on nasal mucosa & skin
Staphylococcus Aureus

virulence factors
Protein A
TSST-1 (toxic shock syndrome)
Enterotoxins-milk/eggs(fast 2-6 hr-food poisoning)
Exfolitins (SSS)
Alpha-toxin (cytolysin)
osteomyolitis

protein A--inhibits phagocytosis--binds Fc portion of antibody

Coagulases--spread
predisposing factors for staph infections
surgery--break in the skin
neutropenia
cystic fibrosis
IV drug abuse--more S.Aureus on the skin than epidermidis
Chronic Granulamatous disease--staph are catalase +
Staphylococcus Aureus

diseases

treatment
infective endocarditis in IV drug users
abcesses
toxic shock syndrome
gastroenteritis (food poisoning from preformed exotoxin--fast onset 2-6hrs- vomiting, diarrhea, nausea)
suppurative lesions (impetigo)
pneumonia--productive w/ fast onset--high rate of necrosis/fatality (nosocomial, ventilator, post influenza, IV drug user, CF, CGD )

Treatment: Methicillin (resistant to PCN)
MRSA-use Vancomycin & fusidic acid
Staphylococcus Epidermidis

labs

diseases
Coagulase negative!
No hemolysis
suspectible to Novobiosin (unlike Staph. Saphrolyticus)

Disease: Catheter & prostetic devise, shunts
Endocarditis in IV drug users (along w/ Staph Aureus)
Staphylococcus Saprophyticus
Coagulase negative
no hemolysis

Novobiocin resistant! (differentiats from S.Epiderm)

UTI's in sexually active young females
Bacillus Anthracis
large gram + rods--boxcar like
Capsule is polypeptide (poly D glutamate)--immunogenic & anti-phagocytic
Aerobic & spore forming

Pathogenesis:
Anthrax toxin-3 protein components (capsule +)
1. protective antigen (B component)--mediates the entry of LF or EF into eukaryotic cell
2. lethal factor--kills cells
3. edema factor--is an adenylate cyclase

reservoir: animal skins, soil--inhalation of spores

cutaneous or pulmonary (life-threatening pneumonia w/ mediastinal hemorrhagic lymphadenitis)

treatment: Ciprofloxacin or Doxycycline (vaccine also available)
Bacillus Cereus
gram + rod, spore former (spores are not killed by boiling), aerobic

Food poisoning: food held warm-not hot (fried rice)
Toxins:
Emetic toxin-fast (1-6 hrs)
Diarrheal toxin-meats & sauces (18 hrs--increases cAMP watery diarrhea)
Listeria

labs & characteristics

reservoir
small gram +, non-spore forming rod
beta-hemolytic (partial-green)
facultative intracellular
tumbling motility
cold growth

Reservoir: animal GI/GU tracts, unpasteurized milk, plants & soil
cold growth: deli meats, soft cheese, coleslaw

foodborne--transmits across placenta or by contact during delivery
Listeria

pathogenesis

diseases
Pathogenesis:
listeriolysin O (beta-hemolysin dumps lysosomal contents into phagosome--"jets" by actin filament formation to next cell)

Diseases: immuno-immaturity--risk for serious infection (babies)
Listeriosis--peaks in summer
healthy pt's--mild diarrhea
pregnant--septicemia
Neonatal:
early-in utero-granulomatosis infanseptice
late-2-3 wks after birth-fecal exposure-meningitis w/ septicemia
Immunocompromised:
Septicemia & meningitis (renal transplant pt's & cancer pt's)

Treatment: Ampicillin (w/ gentamicin for IC pt's)
Corynebacterium Diphteriae

labs
gray/black colonies of club-shaped gram + rods (telluride medium-V or L shape arrangements), non-spore forming, non-motile, aerobic
Granules (volutin) produced on Loeffler's coagulated serum medium stain metachromatically
describe the culture of Streptococcus Pyogenes (group A strep)
gram + cocci in chains
streptococcus pyogenes
identify bacteria
corynebacterium diphteriae
identify bacteria
Pathogenesis of corynebacterium diptheria

disease & tx
non-invasive, colonizes epithelium (resp. drops)

Diphteria toxin: (Elek test)
inhibits protein synthesis by adding ADP ribose to EF-2
Causes:
dirty gray pseudomembrane on oropharynx /larynx/trachea-can obstruct
heart & nerve damage

Disease: Diphteria
sore throat w/ pseudomembrane, bull neck, myocarditis, recurrent laryngeal nerve palsy & lower limb polyneuritis

Treatment: Erythromycin & antitoxin (vaccine-part of DTP, DTaP or Td)
Actinomyces Israelii

characteristics
ANAEROBIC bacteria
gram + rods/branching filaments
not acid fast
sulfur granules and a beaded appearance
Actinomyces Israelii

disease & tx
Actinomycosis

reservoir: endogenous-gums & vag

very invasive-Rib destruction, Cutaneous sinuses, cavitation, spreads to pleura and chest wall (draining abscesses w/ sulfur granules)

"lumpy jaw"-dental trauma or poor hygiene
thoracic-aspiration w/ contagious spread
abdomen/pelvis-surgery/trauma
CNS-solitary abscess

treatment: Ampicillin or Penicillin G and surgical drainage
Nocardia Asteroides

characteristics & reservoir
Aerobic
Partially Acid-Fast
gram + filaments breaking into rods

reservoir: soil & dust

immunosupression & cancer predispose to pulmonary infection
Nocardia Asteroides

disease & tx
Nocardiosis
cavitary bronchopulmonary--cough fever, dyspnea--may spread to brain via blood

cutaneous nocardiosis
starts w/ trauma-cellulitis w/ swelling-draining abscess w/ granules (mycetoma)

treatment: Sulfanamides or TMP/SMX

looks similar to actinomyces but tx totally different-no PCN
nocardia asteroides
caused by a gram+ aerobic, partially acid fast bacteria
Group B strep (S. Agalactiae)
gram + bacitracin resistant (P disk), hippurate utilized, cAMP test positve