Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
15 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
A research laboratory studying virus life cycles has created a continuous culture of bovine kidney fibroblasts that are suitable hosts for a large variety of viral agents. In one experiment, the nuclei of these cells are removed by cytosurgery, and various viral agents are added to the cultures. Following culture of the viruses with the enucleated cells, the yield of cytopathic units of virus is quantified. Which of the following viruses would be capable of replication in enucleated cells?
|
Poliovirus
|
(Microbiology: General Principles, 27%): Most RNA viruses (e.g., poliovirus) replicate in the cytoplasm and therefore can replicate in enucleated cells. Poliovirus belongs to the family Picronaviridae. These vi4ruses are nonenveloped and have an icosahedral nucleocapsid that contains positive-sense RNA. *INFLUENZA CHOICE: THE EXCEPTION TO THE RULE REGARDING RNA VIRUSES IS THE FAMILY ORTHOMYXOVIRIDAE, THE INFLUENZA VIRUSES. ORTHOMYOXOVIRUSES UNDERGO TRANSCRIPTION AND RNA REPLICATION IN THE NUCLEUS OF THE HOST CELL BECAUSE THEY NEED TO CANNIBALIZE THE CAPPED 5' TERMINI OF CELLULAR RNAs FOR USE AS PRIMERS FOR VIRAL mRNA TRANSCRIPTION. FOR MOST DNA VIRUSES, TRANSCRIPTION AND DNA REPLICATION OCCUR IN THE NUCLEUS OF THE HOST CELL. THE EXCEPTION TO THIS OBSERVATION IS THE FAMILY POXVIRIDAE, WHICH CARRIES OUT ITS REPLICATION IN THE CYTOPLASM. POXVIRIDAE INCLUDES VARIOLA VIRUS, VACCINIA VIRUS, MOLLUSCUM CONTAGIOSUM, AND ORF VIRUS. *Adenovirus choice: Adenoviruses are nonenveloped and have an icosahedral nucleocapsid that contains a double-stranded linear DNA genome. *Cytomegalovirus choice: Cytomegalovirus is a member of family Herpes viridae. It is an enveloped virus with an icosahedral nucelocapsid that contains a double-stranded linear DNA genome. *JC virus choice: JC virus belongs to family Papovaviridae. It is nonenveloped and has an icosahedral nucleocapsid that contains a double-stranded circular DNA genome. (POLIOVIRUS:PICORNAVIRIDAE); (POLIOVIRUS:RNA VIRUS); (PICORNAVIRIDAE:NON-ENVELOPED, ICOSAHEDRAL); (PICORNAVIRIDAE:+ RNA); (INFLUENZA VIRUS:ORTHOMYXOVIRIDAE); (ORTHOMYXOVIRUSES:EXCEPTION TO RNAS, TRANSCRIPTION/RNA REPLICATION IN NUCLEUS); (ORTHOMYXOVIRUSES:CANNABILIZE CAPPED 5'TERMINI OF CELLULAR RNAS TO USE AS PRIMERS FOR VIRAL MRNA TRANSCRIPTION); (POXVIRIDAE:EXCEPTION TO DNA VIRUSES, REPLICATES IN CYTOPLASM); (POXVIRIDAE:VARIOLA, VACCINIA, MOLLUSCUM CONTAGIOSUM, AND ORF VIRUS); (ADENOVIRUS:NONENVELOPED, ICOSAHEDRAL NUCLEOCAPSID); (ADENOVIRUS:DS LINEAR DNA); (CMV:HERPES VIRUS, ENVELOPED ICOSAHEDRAL NUCLEOCAPSID); (CMV:DS LINEAR DNA); (JC VIRUS:PAPOVAVIRIDAE); (JC VIRUS:NON-ENVEOPED, ICOSAHEDRAL NUCLEOCAPSID); (JC VIRUS:DS CIRCULAR DNA)
|
|
|
Six days after receiving several flea bites in a rat-infested shed in Southeastern New Mexico, a homeless 24-year-old man develops fever, chills, and a rash that spreads from his abdomen to cover his extremities. He is seen at the local hospital emergency department, where blood is drawn for analysis. Eight days later, the public health department reports the presence of antibody to one of the rickettsial group antigens. Which of the following is the most likely diagnosis?
|
ENdemic typhus
|
(Microbiology: General Principles, 46%): Endemic typus is caused by Rickettsia typhi and is found worldwide. It is spread by the feces of the rat flea, and its reservoir is the rat. *EPIdemic TYPHUS CHOICE: EPIDEMIC TYPHUS IS CAUSED BY RICKETTSIA PROWAZEKII. IT IS PROMINENT DURING TIMES OF WAR AND SOCIAL UPHEAVAL AND IS SPREAD BY THE FECES OF THE BODY LOUS, PEDICULUS HUMANIS. HUMANS ARE THE CHIEF RESERVOIR, ALTHOUGH IT IS ALSO FOUND IN POPULATIONS OF FLYING SUIRRELS ALONG THE ATLANTIC COAST OF THE U.S. *Q fever choice: Q fever is caused by Coxiella burnetii of the family Rickettsiaceae. Unlike the other rickettsial illnesses, Coxiella burnetii is not usually transmitted to humans by the bite of an arthropod. Since the organism is resistant to dehydration, it can be acquired by inhaling dust contaminated by animals with asymptomatic infections, such as goats, sheep, and cattle. *Rocky Mountain spotted fever (RMSF) choice: Rocky Mountain spotted fever is caused by Rickettsia rickettsii. It is transmitted by the bite of an infec5ted tick of the genus Dermacentor. Since the tick passes the infection transovarially to its progeny, the tick is a reservoir. Rodents and other mammals are also reservoirs. Despite the name, most cases of RMSF occur in the central states and southern Atlantic seaboard states. Oklahoma has the highest incidence of the disease. *Scrub typhus choice: Scrub typhus is caused by Rickettsia tsutsugamushi. It occurs mainly in Southeast Asia, where it is transmitted by mites. Mites and rodents are the reservoirs for the organism. (ENDEMIC TYPHUS:RICKETTSIA TYPHI); (RICKETTSIA TYPHI:FECES OF RAT FLEA); (RICKETTSIA TYPHI:RAT RESERVOIR); (EPIDEMIC TYPHUS:RICKETTSIA PROWAZEKII); (EPIDEMIC TYPHUS:WAR); (RICKETTSIA PROWAZEKII:FECES OF BODY LOUS/PEDICULUS HUMANIS); (RICKETTSIA PROWAZEKII:HUMAN/FLYING SQUIRRELS ON EAST COAST RESERVOIRS); (RMSF:RICKETTSIA RICKETTSII); (RMSF:DERMACENTOR TICK); (RMSF:RODENTS/MAMMAL RESERVOIRS); (COXIELLA BURNETII:GOATS, SHEEP, CATTLE); (SCRUB TYPHUS:RICKETTSIA TSUTSUGAMUSHI); (RICKETTSIA TSUTSUGAMUSHI:SE ASIA); (RICKETTSIA TSUTSUGAMUSHI:MITES TRANSMIT); (RICKETTSIA TSUTSUGAMUSHI:MITES/RODENTS RESERVOIRS)
|
|
|
A 68-year-old man presents to his physician with complaints of fatigue and night sweats. Physical examination is remarkable for generalized lymphadenopathy and hepatosplenomegaly. A complete blood count shows anemia, thrombocytopenia, and neutropenia. A peripheral blood smear shows numerous small lymphocytes, some of which appear to have been disrupted during the process of making the smear. Which marker or markers is most likely present on the abnormal cells and could be used to specifically identify such cells in a flow cytometric analyzer?
|
CD 19 and CD 20
|
(Immunology: General Principles, 58%): The patient most likely has chronic lymphocytic leukemia, which usually occur in patients over 50 years of age. The symptoms (which may or may not be present) and the physical findings are classic for this disorder. The peripheral smear usually shows an increased number of small, round lymphocytes, with occasional "smudge cells" (fragile cells disrupted in the process of making a smear). The neoplastic cells have an ummunophenotype somewhat like B cells, with IgM, or IgM and IgD on their surfaces. In addition, both the tumor cells and normal B cells have CD 19 AND 20 markers that aid in their identification on flow cytometry. In CLL, the tumor cells may additionally have CD 5, a T cell marker present on a small minority of normal B cells. *CD 3 CHOICE: THE CD 3 MARKER IS PRESENT ON ALL T CELLS. *CD 8 choice: The CD 8 marker is present on cytotoxic T lymphocytes. *CD 14 choice: The CD 14 marker is used to identify macrophages. *CD 16 and CD 56 choice: The CD 16 and CD 56 markers are present on natural killer (NK) cells. (CLL:CD 19 AND 20 MARKERS); (CLL:CD5); (CD5:T CELL MARKER ON NORMAL B CELLS, BUT FOUND ON TUMOR CELLS); (CD3:ALL T CELLS); (CD14:MACROPHAGES); (CD16 + CD56:NK CELLS)
|
|
|
A 28-year-old male intravenous drug user presents with a febrile illness that has lasted 2 weeks. He also complains of chills, weakness, dyspnea, cough, arthralgia, diarrhea, and abdominal pain. On examination, a heart murmur is present, and small, tender nodules are found on the finger and toe pads, along with small hemorrhages on the palms and soles. Three sets of blood cultures are obtained from different veins. While awaiting laboratory confirmation, an emperic antibiotic regimen should primarily be directed at which of the following organisms?
|
Staphylococcus aureus
|
(Microbiology: General Principles, 83%): NOTE TO SELF: TRUST YOUR INSTINCTS! MY FIRST THOUGHT WAS CORRECT, AND I SECOND-GUESSED MYSELF! *This patient is presenting with signs and symptoms of acute infective endocarditis (IE). The fact that the patient is an intravenous drug user places him at a very high risk for the development of IE. The factors that determine the clinical presentation of IE include the nature of the organism, the valve infected, and the route of the infection. Although the clinical characteristics of IE can vary, most patients present with a febrile illness lasting several days to 2 weeks. This illness is often accompanied by a variety of nonsepcific signs and symptoms, such as chills, weakness, dyspnea, cough, arthralgia, diarrhea, and abdominal pain. Heart murmurs occur in approximately 90% of patients, but may be absent in patients with right-sided infections. Other clinical signs include Osler nodules (purplish or erythematous subcutaneous papules or nodules on the pads of the fingers and toes), Janeway lesions (hemorrhagic painless plaques on the palsm and soles), petechiae (small erythematous painless hemorrhagic lesions that may appear anywhere), and splinter hemorrhages (thin linear hemorrhages found under the nail beds of fingers and toes). The diagnosis of IE is dependent on positive blood cultures and echocardiographic evidence of "valvular vegetation) and/or valvular injury, with echocardiography the preferred method of diagnosis. The initial treatment measures of IE should be aimed at the stabilization of cardiac and/or respiratory symptoms, if applicable. The second priority is obtaining three blood cultures from different veins. Once the blood cultures are obtained, empiric antibiotic therapy for Staphylococci, Streptococci, and Enterococci should be instituted. Since Staphylococcus aureus accounts for most cases of acute IE, emperic coverage should primarily be directed toward Staphylococcus aureus. *Enterococci choice: Enterococci cause a minority of cases of native valve endocarditis, but are not usually involved in endocarditis associated with intravenous drug abuse. *Pseudomonas aeruginosa choice: Gram-negative organisms, such as Pseudomonas aeruginosa, are rarely the cause of IE. *Streptococcus pneumoniae and STREPTOCOCCUS PYOGENES answer choices: Streptococcus pneumoniae and STREPTOCOCCUS PYOGENES ARE NOT COMMON CAUSES OF IE.
|
|
|
A 22-year-old male military recruit complains of a headache and stiff neck. He is examined, blood is drawn, and a lumbar puncture performed. The glucose in the CSF is 100 mg/dL, and the serum glucose is 120 mg/dL. The CSF shows 3 lymphocytes and 0 neutrophils/microliter. Which of the following conclusions concerning the interpretation of these findings is most accurate?
|
There is no evidence for meningitis
|
(Microbiology: Nervous, 47%): NOTE TO SELF: I SECOND-GUESSED THIS ANSWER CHOICE! DON'T THINK TOO MUCH, AS I END UP GETTING THE QUESTION WRONG WHEN I DO! *Both the CSF glucose and the small number of lymphocytes present are within normal limits. It is normal for the CSF glucose to be less than serum glucose, often about 2/3 of the serum value (100 mg/dL in CSF vs. 120 mg/dL in the serum for this case). *"The CSF glucose level suggests bacterial meningitis" and "The lymphocytes suggest bacterial meningitis choices": Bacterial meningitis can profoundly lower CSF glucose levels. CSF from bacterial meningitis cases also usually shows large numbers of neutrophils. *"THE CSF GLUCOSE LEVEL SUGGEST VIRAL MENINGITIS" and "The lymphocytes suggest viral meningitis choices": VIRAL MENINGITIS WILL NOT ALTER THE CSF GLUCOSE LEVEL, but the CSF often contains many lymphocytes.
|
|
|
A 67-year-o0ld woman in a skilled nursing facility complains of flu-like symptoms. After several days, she develops high fever, dyspnea, and a productive cough. The nurses also notice mental status changes, and she is transported to the nearby community hospital. A chest x-ray shows a cavitary lesion in her left lung. Which of the following organisms would most likely be identified from examination of her sputum?
|
Staphylococcus aureus
|
(Microbiology: Respiratory, 32%): The woman has developed a pulmonary abscess, as evidenced by the chest radiograph. Of the organisms listed, Staph. Aureus is the most likely cause of bacterial pneumonia complicated by abscess formation. Bacgeria commonly producing pneumonia developing in the contex of influenza include: Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pneumoniae, but Streptococcus pneumoniae is not a frequent cause of lung abscesses. *Candida albicans answer choice: Candida albicans would not be a likely cause of this woman's abscess, or of the pneumonia that preceded it. *KLEBSIELLA PNEUMONIA CHOICE: KLEBSIELLA PNEUMONIAE IS MORE LIKELY IN MEN WHO ARE ALCOHOLIC OR DIABETIC, OR SUFFERING FROM CHRONIC OBSTRUCTIVE LUNG DISEASE. *Pneumocystis carinii choice: Penumocystis carinii is associated with pneumonia in immunocompromised hosts, but there is no indication of immune compromise in this patient. *Streptococcus pneumonia choice: Streptococcus pneumonia is only rarely associated with lung abscess. (BACTERIAL PNEUMONIA + ABSCESS IN WOMEN:S. AUREUS); (BACTERIAL PNEUMONIA + INFLUENZA:S. AEREUS, STREPTOCOCCUS, AND HAEMOPHILUS); (KLEBSIELLA PNEUMONIA:MEN, ALCOHOLIC, DIABETIC, OR COPD)
|
|
|
A sexually active 25-year-old man develops epididymitis and orchitis. Needle biopsy demonstrates a prominent leukocytic infiltrate with numerous neutrophils. Which of the following organisms is the most likely cause of this man's infection?
|
Neisseria gonorrhoeae
|
(Microbiology: Reproductive, 82%): Acute epididymitis and orchitis with prominent neutrophils in a sexually active male are most likely due to infection with Neisseria gonorrhoeae or Chlamydia trachomatis. N. gonorrhoeae can produce a nonspecific pattern of acute inflammation (nonspecific epididymitis and orchitis) or can be sufficiently severe as to cause frank abscesses within the epididymis. NOTE: THE KEY TO THIS QUESTION IN DIFFERENTIATING SYPHILIS VS. GONORRHEAE IS THE MENTION OF *NEUTROPHILS* IN THE QUESTION STEM! (NEUTROPHILS:GONORRHEAE AS PLASMA CELLS:SYPHILIS) *Escherichia coli choice: Escherichia coli is an important cause of nonspecific epididymitis and orchitis in children with congenital genitourinary abnormalities and in older men. *Mycobacterium tuberculosis choice: Mycobacterium tuberculosis can cause tuberculosis of the epididymis and tests, characterized by granuloma formation. *Pseudomonas sp choice: Pseudomonas sp. has been implicated as an important cause of nonspecific epididymitis and orchitis in older men. *TREPONEMA PALLIDUM: TREPONEMA PALLIDUM, THE CAUSATIVE AGENT OF SYPHILIS, CAN CAUSE TESTICULAR INVOLVEMENT WITH GUMMA FORMATION, ENDARTERITIS, AND/OR A PROMINENT *PLASMA CELL* INFILTRATE.
|
|
|
A 67-year-old man with moderate renal dysfunction presents with influenza-like symptoms. The patient also has a red macular rash that first appeared on the ankles, then spread centrally. He reports nausea, vomiting, and profound restlessness. He states that he was recently hiking with some friends in the mountains, about a week ago. Rickettsia rickettsiae is demonstrated by immunohistochemistry on skin biopsy. Which of the following agents would be most appropriate to treat this patient's infection?
|
Doxycycline
|
(Microbiology: General principles, 65%): This patient has Rocky Mountain spotted fever. This diagnosis can be confirmed with the immunohistologic demonstration of R rickettsiae in the skin biopsy. The tetracyclines are a class of antibiotics commonly used in the treatment of rickettsial infections, acne, and various sexually transmitted diseases, as well as in the treatment of infections caused by susceptible organisms in penicillin-allergic patients. The key to this question is knowing which tetracycline antibiotic is safest to administer to a patient with renal dysfunction. Doxycycline is secreted in an inactive form into the intestinal lumen and eliminated in the feces; therefore, its half-life is largely independent of renal or hepatic function. The other tetracyclines listed are concentrated by the liver in the bile and exreted in the urine and feces unchanged. Therefore, dosage adjustments need to be made in patients with renal impairment because of accumulation of the drug in the body. In other words, demeclocyline, methacycline, oxytetracycline, and TETRACYCLINE WILL ACCUMULATE IN PATIENTS WITH RENAL IMPAIRMENT (DOXYCYCLINE:ONLY FECALLY ELMINATED, GOOD FOR RENAL FAILURE)
|
|
|
A 57-year-old fisherman with a history of alcoholism is hospitalized in Gulfport, Mississippi with a 1-day history of severe, watery diarrhea after eating several raw oysters. He is badly dehydrated on admission, and has numerous fluid-filled vesicular lesions on his legs. Within 12 hours, he becomes severely hypotensive and dies. Which of the following pathogens is the most likely cause of this man's death?
|
Vibrio vulnificus
|
(Microbiology: GI, 73%): NOTE TO SELF: I FELT OF TWINGE OF HESITANCE IN PUTTING DOWN THE "MORE FAMILIAR" ANSWER. THIS TELLS ME THAT I NEED TO RELY MORE ON GUT INSTINCT! *Vibrio vulnificus is an extremely invasive organism, producing septicemia in patients after eating raw shellfish, or causing wound infections, cellulitis, fasciitis, and myositis after exposure to seawater or after cleaning shellfish. Patients at high risk for septicemia include those with liver disease, congestive heart failure, diabetes mellitus, renal feailure, hemochromatosis, and immunosuppression. Symptoms after ingestion include fever, chills, hypotension, and fluid-filled blisters progressing to muscle necrosis, especially affecting the lower limbs. *Citrobacter diversus choice: Citrobacter diversus produces neonatal meningitis and can be frequently cultured from the umbilicus. *Enterotoxigenic E. coli choice: Enterotoxigenic E. coli produces the classic traveler's diarrhea. The toxin is ingested in water and salads. The incubation period is approximately 12 hours. The diarrhea is non-inflammatory and treatment is supportive. *Providencia stuartii choice: Providencia stuartii is a gram-negative rod related to Proteus. It is a common cause of nosocomial bacteremia in nursing home patients with chronic catheterization. *VIBRIO CHOLERAE: VIBRIO CHOLERAE PRODUCES A NON-INVASIVE, NON-INFLAMMATORY, HIGH-VOLUME SECRETORY DIARRHEA THAT IS TOXIN-MEDIATED.
|
|
|
A man presents to a dermatologist because of a severe mucocutaneous rash that involves most of his body, including his palms and soles. Questioning revleas that he is a merchant marine who, several months previously, had an encounter with a prostitute in Southeast Asia. Which of the following is the most likely causative agent of this rash?
|
Treponemia palldium
|
(Microbiology: Skin/Connective Tissue, 82%): The rash described is that of secondary syphilis, caused by Treponema pallidum. Involvement of palsm and soles by a rash is unusual, and secondary syphilis should come to mind. Not all patients with secondary syphilis have a severe form of the rash, and sonsequently some cases are missed. Primary syphilis takes the form of a painless, button-like mass called chancres. Tertiary syphilis, which is now rare, has a propensity for involving the aorta and central nervous system and can also cause "gummas" (granulomatous-like lesions) in many sites, notably including liver and bone. *Herpes simplex I choice: Herpes simplex I usually causes perioral vesicular lesions. *HERPES SIMPLEX II CHOICE: HERPES SIMPLEX II USUALLY CAUSES GENITAL VESICULAR LESIONS *HIV choice: HIV does not itself cause a rash, although co-infection with other organisms can result in a rash. *Neisseria gonorrhoeae choice: Neisseria gonorrhoeae does not typically cause a rash. (RASH, STD:SYPHILIS); (GUMMAS:SYPHILIS); (GUMMAS:LIVER/BONE)
|
|
|
A number of encapsulated organisms are capable of entering the body across the respiratory mucosa. If these organisms enter the bloodstream, delivery to the meninges is a risk. Streptococcus pneumoniae, Hemophilus influenzae, Neisseria meningitidis, and Cryptococcus neoformans are all capable of making this transition. Which of the following is the most important immunological protective mechanisn against such blood-borne encapsulated organisms?
|
IgG-mediated osponization in the spleen
|
(Immunology: General Principles, 42%): YET ANOTHER EXAMPLE OF WHERE I FELT A "TWINGE" AND CHOSE THE "SAFE ANSWER!" TAKE THE RISK! TRUST YOUR GUT! *IgG is the predominant antibody in the serum. Encapsulated organisms are resistant to phagocytosis, but opsonization (enhancement of phagocytosis with IgG and/or C3b) is the most important mechanism for removing these pathogens from the bloodstream in the spleen. *C3 nephritic factor choice: C3 nephritic factor is an IgG autoantibody that binds to C3 convertase, making it resistant to inactivation. This leads to persistently low serum complement levels and is associated with Type II membranoproliferative glomerulonephritis. *C5-9-mediated lysis choice: C5-9-mediated lysis is a secondary mechanism of destruction of encapsulated bacteria, since the capsule tends to protect against complement-mediated lysis. C5-9 is also known as the membrane-attack complex of complement. *Myeloperoxidase in phagocytic cells choice: Myeloperoxidase in phagocytic cells is an element of the oxygen-dependent intracellular pathway that effectively kills ingested organisms. The most efficient bactericidal system in phagocytes is dependent on NADPH oxidase, and the myeloperoxidase system is the next most powerful. *SECRETORY IGA ANSWER CHOICE: SECRETORY IGA IS THE IMMUNOGLOBULIN ASSOCIATED WITH MUCOUS MEMBRANES. ALTHOUGH THE PATHOGENS MENTIONED ALL ENTER THE BODY ACROSS THE MUCOUS MEMBRANES, THE QUESTION ASKS ABOUT THE *MOST IMPORTANT PROTECTIVE MECHANISM ONCE THEY ENTER THE BLOOD.* (c3 NEPHRITIC FACTOR:IGG AUTOANTIBODY); (C3 NEPHRITIC FACTOR:BINDS C3 CONVERTASE); (C3 NEPHRITIC FACTOR + C3 CONVERTASE:RESISTANT TO INACTIVATION); (C3 NEPHRITIC FACTOR BINDING TO C3 CONVERTASE:LOW SERUM COMPLEMENT LEVELS, TYPE II MPGN)
|
|
|
A 24-year-old man presents with fever, rash, a mild headache, and a sore throat. He denies HIV risk factors, although he is sexually active. On examination, his temperature is 100.8 degrees Fahrenheit, and his pulse is 90/minute. There is a diffuse, erythematous, maculopapular rash over most of his body. Generalized adenopathy is appreciated, and photophobia is noted when fundoscopic examination is attempted. If this man is not treated, which of the following changes in his serologic status will most likely occur?
|
The VDRL titer would fall
|
(Microbiology: General Principles, 23%): This is a case of syphilis, which is diagnosed serologically, using either treponemal or nontreponemal tests. The FTA-ABS (fluorescent treponemal antibody-absorbed test) is the most widely used of the specific tests and depends on fluorescent labeling of the organisms with anti-treponemal antibody. The specific tests tend to rise early in titer and stay elevated throughout the lifetime of the host, or at least untill well after drug therapy has been completed. The VDRL (Venereal Disease Research Laboratory) is a nontreponemal test that detects antibodies that cross-reavct with mammalian cardiolipid called reaginic antibodies. This test will become positive after the specific test, and its titer will fall late in infection, with or without drug therapy. *"The FTA-ABS titer would fall" answer choice: The FTA-ABS titer would fall is incorrect because this titer will remain high throughout the life of the host, falling off only very slowly after drug cure. *"The FTA-ABS titer would rise" answer choice: The FTA-ABS titer would rise is incorrect because the specific antibody test will reach a high positive tier and remain at that level in untreated late stage syphils. *"The VDRL titer would rise" answer choice: The VDRL titer would rise is incorrect because reaginic antibody levels will fall in late stage syphilis, with or without drug treatment. *"Both FTA-ABS and VDRL would fall" answer choice: Both FTA-ABS and VDRL would fall is incorrect because specific antibody levels would remain high, while reaginic antibodies would fall. *"BOTH FTA-ABS AND VDRL WOULD RISE" ANSWER CHOICE: BOTH FTA-ABS AND VDRL WOULD RISE IS INCORRECT BECAUSE SPECIFIC ANTIBODY LEVELS WOULD REMAIN HIGH, WHILE REAGINIC ANTIBODIES WOULD FALL.
|
|
|
A 25-year-old man presents with a high fever and generalized malaise. His condition deteriorates so rapidly that his friends decide to take him to the emergency department 24 hours after the onset of symptoms. He has a history of intravenous drug abuse. A test for anti-HIV antibodies is negative. Phbysical examination reveals a systolic murmur, and echocardiography shows bulky vegetations attached to the tricuspid valve leaflets. Which of the following microorganisms will be most likely isolated from this patient's blood cultures?
|
Staphylococcus aureus
|
(Microbiology: Cardiovascular, 72%): The patient has a fever and is extremely ill. The most important clue to the diagnosis is the presence of bulky vegetations on the tricupsid valv e, indicating that he has infective endocarditis. On the basis of the rapid clinical course, this is likely a case of acute infective endocarditis. The diagnosis of this condition must be confirmed by blood cultures, which are also necessary to determine bacterial antibiotic sensitivity. *S. AUREUS (COMMONLY PRESENT ON THE SKIN) IS THE MOST FREQUENT ETIOLOGIC AGENT OF INFECTIVE ENDOCARDITIS IN INTRAVENOUS DRUG ABUSERS.* (S. AUREUS:IV DRUG USE). It commonly affects the tricuspid valve. Because of its high virulence, S. aureus-related endocarditis follows an acute course and may lead to death within a few days. *Candida albicans choice: The causative agents of infective endocarditis differ depending on host factors. Fungal organisms, such as Candida albicans, may cause infective endocarditis in severely immunosuppressed patients, such as those with AIDS. *Hemophilus influenzae choice: A minority of cases of infective endocarditis are caused by a number of normal commensals in the oral cavity, i.e., the "H.A.C.E.K." group: H.emophilus, A.ctinobacillus, C.ardiobacterium, E.ikenella, and K.ingella. *STAPHYLOCOCCUS EPIDERMIDIS CHOICE: S. EPIDERMIDIS AND OTHER COAGULASE-NEGATIVE STAPHYLOCOCCI TEND TO PRODUCE ENDOCARDITIS IN RECIPIENTS OF *PROSTHETIC VALVES.* (S. EPIDERMIDIS:PROSTHETIC VALVES) *Viridans (alpha-hemolytic) streptococci choice: Viridans streptococci are the most frequent agents causing endocarditis in previously abnormal valves, such as those damaged by rheumatic disease, or congenitally abnormal valves. Coagulase-negative staphylococci and viridans (alpha-hemolytic) streptococci are less virulent than S. aureus and are thus associated with a subacute (more prolonged) clinical course and a better prognosis.
|
|
|
A biology teacher from North Carolina regularly spends her summer vacations leading nature walks through an arboretum on Cape Cod in Massachusetts. Two weeks after her arrival on the island, she calls in sick, complaining of fever, headache, and muscle soreness. After three days of self-medication with over-the-counter drugs and no symptomatic improvement, she seeks medical attention at a local emergent care clinic. The physican who sees her finds her to be mildly febrile and tachycardic, but finds no evidence of pharyngitis, abnormal breath sounds, or skin rash. A blood film is notable for the presence of multiple, berry-like cytoplasmic inclusion bodies in her granulocytes. What is the most likely causative agent?
|
Anaplasma phagocytophilum
|
(Microbiology: Multi-system, 17%): This woman has the symptoms and signs of human granulocytic ehrlichiosis, caused by Anaplasma phagocytophilum. This disease coexists in the same geographic region as Lyme disease because it is transmitted by the same ixodid tick vector. This same tick can transmit three separate infections: Lyme disease, ehrlichiosis, or babesiosis. The finding of Rocky Mountain Spotted Fever-type symptoms (absent rash) and the presence of berry-like clusters (morulae) inside neutrophils is diagnostic. *Bartonella henselae answer choice: Bartonella henselae is the agent of bacillary angiomatosis in AIDS patients and cat scratch disease in children. Cat scratch disease is a febrile lymphadenopathy, and bacillary angiomatosis is a proliferative disease of small blood vells of the skin and viscera. *COXIELLA BURNETII CHOICE: COXIELLA BURNETII IS THE AGENT OF Q FEVER. THIS RICKETTSIA-LIKE ORGANISM IS TRANSMITTED BY INHALATION OF AEROSOLS FROM INFECTED ANIMAL TISSUES. IT WOULD NOT PRODUCE MORULAE INSIDE GRANULOCYTES. *Ehrlichia chafeensis choice: Ehrlichia chafeensis is the agent of human monocytic ehrlichiosis. It causes the production of morulae in monocytes and macrophages, and is most common in the southeastern and lower Midwestern states. *Rickettsia rickettsiae choice: Rickettsia rickettsiae is the agent of Rocky Mountain Spotted Fever. Although the symptoms of fever, myalgia, and headache are consistent in this woman, the organism produces a characterstic centripetal rash that beings on the ankles and wrists and spreads toward the trunk. (HUMAN GRANULOCYTIC EHRLICHIOSIS:ANAPLASMA PHAGOCYTOPHILUM); (IXODES TICK:LYME DISEASE, EHRLICHIOSIS, OR BABESIOSIS); (BERRY-LIKE CLUSTERS:MORULAE); (MORULAE INSIDE NEUTROPHILS:ANAPLASMA PHAGOCYTOPHILUM) (BACILLARY ANGIOMATOSIS IN AIDS PATIENTS:BARTONELLA HENSELAE); (BACILLARY ANGIOMATOSIS:PROLIFERATIVE DISEASE OF SMALL BLOOD VESSELS OF SKIN/VISCERA); (EHRLICHIA CHAFEENSIS:HUMAN MONOCYTIC EHRLICHIOSIS); (HUMAN MONOCYTIC EHRLICHIOSIS:MORULAE IN MONOCYTES/MACROPHAGES); (HUMAN MONOCYTIC EHRLICHIOSIS:MOST COMMON IN SE/LOWER MIDWESTERN STATES);
|
|
|
A 10-year-old boy is attending summer camp in Texas. After 2 weeks of camp, he complains of a sore throat, headache, cough, and malaise. On physical examination, he also has a low-grade fever, and keratoconjunctivitis. Within hours, several other campers and counselors visit the infirmary with similar symptoms. All of the patients had been swimming in the camp swimming pool. Eventually, more than 50% of the camp complain of symptoms similar to the initial case that last 5 to 7 days. Which of the following is the most likely causative organism?
|
Adenovirus
|
(Microbiology: Multi-system, 68%): Adenoviruses are non-enveloped (naked), icosahedral DNA viruses causing a variety of clinical syndromes. Adenoviruses cause a pharyngoconjunctivitis that affects children and sometimes adults who are living in the same household. Contaminated swimming pools have been implicated as sources for the virus. The virus is latent in the lymphoepithelial tissue of the nasopharynx and other sites. Adenoviruses also cause watery, non-bloody diarrhea. *Chlamydia choice: Chlamydia spp. produce a variety of clinical syndromes, including a sexually transmitted urethritis, pelvic inflammatory disease, neonatal pneumonia, and inclusion conjunctivitis, lymphogranuloma venereum, adult interstijtial pneumonia, and a zoonotic pneumonitis. *Gram-negative diplococcus choice: A gram-negative diplococcus would be a Neisseria spp. or Moraxella. Neisseria meningitidis would be the logical choice, since it is associated with outbreaks among children. However, the clinical syndrome caused by infection with the meningococcus is one of a fulminating, progressive septicemia and/or meningitis with fever, vascular collapse, and disseminated intravascular coagulation. N. gonorrhoeae does not cause a clinical syndrome as described in the question. Moraxella catarrhalis causes pneumonia in patients with chronic obstructive pulmonary disease. *GRAM-POSITIVE ENTEROCOCCUS ANSWER CHOICE: GRAM-POSITIVE ENTEROCOCCUS WOULD REFER TO GROUP D STREPTOCOCCUS. THESE ORGANISMS ARE ASSOCIATED WITH ENDOCARDITIS AND GENITOURINARY INFECTIONS. *Herpesvirus choice: Herpesviruses are large, enveloped DNA viruses with an icosahedral shape. Possible diagnoses for this patient include Epstein-Barr virus, producing infectious mononucleosis, or cytomegalovirus, producing a mononucleosis-like syndrome. The patients in the question did not have hepatosplenomegaly (characteristic of mononucleosis), but did have keratoconjunctivitis. The organisms causing the outbreak in the question also has a higher level of infectivity and a short incubation time. (ADENOVIRUS:KERATOCONJUNCTIVITIS)
|
