Microbiology ASCP Q's

96. Which is the best test for determining the likelihood of progression to cirrhosis in a patient with chronic HCV? A. liver biopsy B. quantitative HCV RNA C. qualitative HCV RNA D. serial ALT levels E. HCV serotype determination

A. liver biopsy. All of the tests mentioned have a role in the diagnosis and management of HCV. However, only liver biopsy can provide the data required to grade inflammation and stage fibrosis of liver infection. QCCP2,HCV

133. Where do Plasmodium sporozoites proliferate? A. liver B. red blood cells C. bone marrow D. within nucleated erythrocyte precursors E. freely within the blood

A. liver. After sporozoites are introduced into the blood stream by an anopheline mosquito, they travel to the liver to proliferate. The infected hepatocytes rupture and release the merozoites, which infect RBCs. Hypnozoites are the forms that maintain a latent infection in the liver. QCCP2, Plasmodium

Which of the following viruses is the most common cause of winter viral encephalitis? A. lymphocytic choriomeningitis virus B. Coxsackie A virus C. Coxsackie B virus D. human herpes virus 6 E. West Nile virus

A. lymphocytic choriomeningitis virus. LCMV is the most common cause of winter/spring viral encephalitis, while enteroviruses such as Coxsackie, are the main causes of summer/fall epidemics. LCMV is spread to humans through contact with infected mouse feces. QCCP2,Meningitis, specific agents

101. What's the most common secondary complication that can arise with measles infection? A. otitis media B. pneumonia C. myocarditis D. appendicitis E. subacute sclerosing panencephalitis

A. otitis media. Superinfection can cause otitis media or pneumonia, especially in immunocompromised patients. All of the other choices can happen with measles infection but for the most part are rare, especially SSPE. QCCP2,Measles

71. All of the following factors affect the rate of CMV seropositivity? A. pregnancy status B. locale C. age D. socioeconomic status E. all of the above affect the seropositivity rate

A. pregnancy status. While the effects of primary and reactivated CMV infection in pregnant women are potentially dire, there is no statistically significant effect on the rate of seropositivity. The rate of seropositivity in Africa is much greater than most of the rest of the world. The risk of CMV infection increases with age (presumably due to increased risk of exposure). Also, lower socioeconomic status is associated with increased CMV seropositivity. QCCP2,CMV

73. What's the most common means of transmission of EBV? A. saliva B. blood C. fecal oral D. respiratory droplet E. solid organ transplantation

A. saliva. They don't call it the kissing disease for nothing! A less common means of transmission is through blood transfusion or solid organ transplantation. Nearly 90% of people in the world have been infected with EBV. QCCP2,EBV

128. The only medically significant ciliate organism is: A. Entamoeba histolytica B. Balantidium coli C. Cryptosporidium parvum D. Chilomastix mesneli E. Cyclospora cayetenensis

B. B . A 50-70 micron organism with circumferential ciliation and a lenticulate nucleus, B. coli is the most medically significant ciliate (and the only one you probably have to be aware of). QCCP2,Ciliates

74. Which cell surface antigen is the receptor for the Epstein-Barr virus? A. P antigen B. CD21 C. insulin-degrading enzyme D. CD4 E. Cd81

B. CD21. The C3d receptor, or CD21, functions as the target for EBV cell entry. P antigen (associated with Donath-Landsteiner ab), paroxysmal nocturnal hemoglobinuria, neutralized by pigeon egg and hydatid cyst fluid) is the parvovirus receptor. Insulin-degrading enzyme is the putative receptor for varicella-zoster virus, while CD4 is the receptor for HIV. Recent studies suggest that CD81 may have a role as a receptor for HCV. QCCP2,EBV

70. Which of the following viruses is responsible for the most common congenital infection in the United States? A. VZV B. CMV C. parvovirus B19 D. EBV E. adenovirus

B. CMV. Passed transplacentally, the risk of in utero infection is greatest when the mother acquires a primary CMV infection while pregnant. The effects from in utero infection can range from severe to mild, with the most common manifestation of sensorineural hearing loss. QCCP2,CMV

117. Which of the following organisms can be detected with the "adhesive tape" test? A. Giardia lamblia B. Enterobius vermicularis C. Strongyloides stercoralis D. Onchocerca volvulus E. Brugia malayi

B. E. The adult female worm migrates to the anal verge at night to lay eggs. This accounts for the nocturnal anal pruritus that is a symptom of enterobial infection. Some of the eggs that are laid by the female worm can be collected with adhesive tape applied to the anus at night. QCCP2,Cellophane tape

90. The persistence of which marker is the best evidence of chronic HBV infection: A. HBeAg B. HBsAg C. anti-HBe D. anti-HBs E. anti-HBc

B. HBsAg. The persistence of surface antigen is an excellent indicator of chronicity. With acute infection and resolution, surface antigen peaks 2-3 months post-infection and before symptoms, but is completely gone before 6 months, to be replaced by anti-surface antibody (HBsAb) and the clinical symptoms of acute hepatitis. In chronic infection, the surface antibody does not appear, while the surface antigen persists. QCCP2,F3.2 - 3.3

Which of the following organisms is the most common cause viral myocarditis? A. adenovirus B. JC virus C. Coxsackie A D. Coxsackie B E. human herpes virus 6

D. Coxsackie B. Coxsackie A and B are frequently confused for each other when it comes to the diseases that they each cause. Coxsackie A causes hand-foot-mouth disease, so named for the most common locations of the lesions. Coxsackie B, on the other hand, is responsible for the majority of cases of viral myocarditis. QCCP2,T3.2

124. Which amoeba is most often seen as a coinfection with Enterobius vermicularis? A. Naegleria B. Acanthamoeba C. Entamoeba histolytica D. Dientamoeba E. Iodamoeba

D. D. With two nuclei and a fractured central karyosome, Dientamoeba is often seen coinfecting with Enterobius. Like Enterobius, D. fragilis causes diarrhea and pruritus ani. QCCP2, Dientamoeb

89. In a person vaccinated against hepatitis B virus several years prior, which serological marker would be expected? A. HBsAg B. HBeAg C. IgG anti-HBc D. HBsAb E. anti-HBc

D. HBsAb. All of the other choices, with perhaps the early appearance post-vaccination of HBsAg, should not be seen in a vaccinated individual. HBeAg is present during active viral replication, while anti-HBc is present only in someone who has resolved an acute infection. It is the same with anti-HBe, though this is less associated with resolution than with someone who has just had the HBeAg turn negative in testing. QCCP2,HBV

Latex agglutination tests on CSF are commonly used for the diagnosis of all of the following causes of meningitis, except: A. Haemophilus influenzae, type B B. Neisseria meningitidis C. group B Streptococcus D. Listeria monocytogenes E. Streptococcus pneumoniae

D. Listeria is a very difficult organism to identify in CSF. Gram stain sensitivity is less than 50% and there is no commercially available latex agglutination test at this time. Culture is the main source of positive identification. QCCP2,Laboratory evaluation

127. What characteristic feature of T. cruzi trypomastigotes helps distinguish it from T. brucei in peripheral blood smears? A. undulating flagellum B. central kinetoplast C. culture on Novy-MacNeal-Nicolle medium D. presence in lymph nodes E. "C" shape

E. "C" shape. The other features mentioned are shared to some extent by both species of trypanosomes. The characteristic "C" shape (remember - Cruzi, Chagas, "C"-shape) helps to identify Trypanosoma cruzi compared to the more randomly curved trypomastigotes of T. brucei. QCCP2,Trypanosoma spp

98. Which of the following viruses is hemagglutinin-positive? A. influenza A B. influenza B C. parainfluenza D. A & B E. A, B, C

E. A, B, C. A viral surface protein, hemagglutinin, binds to sialic acid receptors on the surface of respiratory epithelial cells and in turn are expressed on the surface of infected cells. The hemagglutinin has the ability to agglutinate red blood cells, which is the basis of the diagnostic hemadsorption test. QCCP2,Orthomyxoviruses

116. Which of the following organisms is detectable with modified acid-fast stains? A. Cryptosporidium B. Cyclospora C. Isospora D. A & B E. A, B, C

E. A, B, C. All of the above parasites are potentially positive for acid-fast staining, improving the chances of detection notably. The related organism microsporidium is not acid-fast and may require more invasive means for diagnosis. QCCP2,Parasites, specimens

84. Which of the following clinical presentations is associated with HHV8? A. Kaposi sarcoma B. primary effusion lymphoma C. multicentric Castleman disease D. A & B E. A, B, C

E. A, B, C. Especially in the immunocompromised patient, HHV8, or KSHV, is responsible for a number of disease processes. The etiologic agent in these cases is identified by FISH, PCR, IHC, or serological means. QCCP2,HHV8

80. Which of the following antibodies is most helpful in distinguishing an acute EBV infection from a remote EBV infection? A. IgM anti-EA B. IgM anti-VCA C. IgG anti-EA D. IgM anti-VCC E. IgG anti-EE

B. IgM anti-VCA. Anti-viral capsid antibodies (VCA) are the only EBV antibodies with a high specificity for the acute phase of infection. This IgM antibody is the first antibody to appear with acute infection but quickly decreases in titer with time. IgM anti-VCA recedes to undetectable titers with convalescence but quickly reappears with virus reactivation. QCCP2,EBV

61. Which of the following viruses causes syncytia formation in culture? A. RSV B. measles C. HSV D. A & B E. A, B, C

E. A, B, C. If you think about the histopathology of these viruses, it helps. RSV of course causes syncytia formation - it's in the name! Measles infection can cause the formation of Warthin-Finkeldey giant cells, and then there's the 3 Ms describing the nuclei of cells infected with HSV - multinucleation, margination, and molding. QCCP2,T3.6, viral histology

136. All of the following features of Plasmodium falciparum are helpful in distinguishing it from P. vivax or P. ovale, except: A. multiple ring forms within an erythrocyte B. applique trophozoite forms C. enlarged infected red blood cells D. banana-shaped gametocytes E. double chromatin dots in ring forms

C. enlarged infected RBCs. Unlike P. ovale and P. vivax, P. falciparum-infected RBCs tend not to be enlarged. Schuffner dots are also a characteristic of P. vivax and P. ovale. QCCP2, Plasmodium

72. All of the following techniques are routinely used to diagnose CMV, except: A. culture B. PCR C. flaccid paralysis in suckling mice injected with patient serum D. direct fluorescent antibody E. serology

C. flaccid paralysis in suckling mice after injection. In addition to tissue histology looking for the characteristic nuclear owl eye, inclusions can be performed if diagnostic tissue is available. Observation of flaccid paralysis in suckling mice is used to diagnose Coxsackie A virus. QCCP2,CMV

78. Which of the following antibodies can be produced in response to EBV infection? A. anti-i B. ANA C. Paul-Bunnell heterophile antibodies D. A & B E. A, B, C

E. A, B, C. In addition, rheumatoid factor levels may be increased. For this reason and because the culture of EBV is difficult, routine diagnosis is usually made serologically. QCCP2,EBV

114. Which of the following HIV tests is the assay for determining response to anti-retrovirals? A. serum ELISA B. Western blot C. quantitative HIV RNA D. CD4 count E. p24 antigen detection

C. quantitative HIV RNA. Quantitative HIV RNA is an assessment of viral load. Quantitation of RNA levels is an excellent prognostic tool to predict progression, especially long-term. QCCP2,HIV

115. Which test is the best choice for the detection of HIV infection shortly after an infection? A. serum ELISA B. Western blot C. quantitative HIV RNA D. CD4 count E. p24 antigen detection

C. quantitative HIV RNA. The sensitivity of quantitative HIV RNA approaches 100%; however, the specificity is less. In a confirmatory test, you would like optimal specificity, unlike screening tests where you would like the sensitivity to be high. QCCP2,HIV

112. Which of the following is/are characteristic of adult T cell lymphoma? A. peripheral CD4+/CD25+ flower cells B. hypercalcemia C. high serum IL-2 receptor D. A & B E. A, B, C

E. A, B, C. Patients can also have skin rash and extreme thirst. Interestingly, the neoplastic cells express CD25, which is the IL-2 receptor, as well as high levels of free IL-2 receptor in the serum. The usual incubation time for ATCL is 20-30 years. QCCP2,HTLV-I

64. Which of the following herpes virus family members lie latent in the dorsal root ganglia? A. HSV-1 B. HSV-2 C. VZV D. A & B E. A, B, C

E. A, B, C. The HSV family of viruses is made up of the prototypical enveloped DNA viruses. Three of the members lie dormant within dorsal root ganglia until they are reactivated. QCCP2,Human herpes viruses, T3.8

130. Which of the following organisms is in the differential diagnosis of the bradyzoite of Toxoplasma gondii? A. Leishmania B. Histoplasma C. Trypanosoma D. A & B E. A, B, C

E. A, B, C. The bradyzoite forms of Toxoplasma are small intracellular organisms seen within the cytoplasm of histiocytes, while the tachyzoites are curved extracellular organisms. A histiocyte filled with Toxoplasma bradyzoites resembles Leishmania, Histoplasma, Trypanosoma, and Coccidioides, and must be distinguished. QCCP2, Toxoplasma

82. LMP1 and EBER staining show high concordance in which of the following lesions? A. Hodgkin lymphoma B. post-transplant lymphoproliferative disorder C. infectious mononucleosis D. A & B E. A, B, C

E. A, B, C. The positive correlation between the two stains is highest when observed in the cells that are of interest. LMP1 has a modest false positive rate which can be overcome by narrowing the observation to the cells of interest. QCCP2,EBV

67. All of the following features are used to diagnose congenital varicella, except: A. maternal VZV during pregnancy B. skin lesions in newborn in a dermatomal distribution C. serological evidence of newborn infection with elevated specific IgG persisting beyond 7 months D. serological evidence of newborn infection with elevated specific IgM E. all of the above are potentially utilized in the diagnosis of congenital varicella

E. All of the above are potentially utilized in the diagnosis of congenital varicella. The incidence of perinatal varicella is highest when the mother contracts VZV within a few days of delivery, with the incidence declining inversely with gestational age. Because of the extremely high infectivity of VZV contracted perinatally (50-60%), VZ immunoglobulin is recommended for prophylaxis, perhaps along with acyclovir. QCCP2,VZV

All of the following viruses are most commonly detected by culture, except: A. HSV-1 B. HSV-2 C. adenovirus D. HPV E. EBV

E. EBV. EBV, along with rubella and the arboviridae, are not routinely cultured, but rather diagnosed based on the positive serology. Similarly, rota- and rhabdoviruses are not cultured; their diagnosis depends on virus-specific antigen detection. QCCP2,Virology Laboratory Methods

110. Negri bodies in Purkinje cells are associated with which of the following viruses? A. paramyxoviruses B. Eastern equine encephalitis C. rhabdovirus D. lymphocytic choriomeningitis virus E. Ebola virus

C. rhabdovirus. Rabies virus is transmitted through bites by contaminated animals. In most of the world, that means dogs and cats. In areas where the domestic causes are controlled, non -domestic animals, such as bats, skunks, and foxes are responsible for the transmission of the majority of cases. QCCP2, Family Rhabdoviridae,

65. Why is caesarean section delivery of children from mothers with prodromal or active genital herpes recommended? A. increased risk of vaginal trauma to the mother B. indication of immunodeficiency in mother and increased risk of secondary infection C. to decrease the risk of neonatal herpes D. to decrease the risk of spreading infection to health care workers E. to decrease risk of puerperal coinfection

C. to decrease the risk of neonatal herpes. Vertical transmission of HSV from genital lesions to an infant can cause neonatal HSV infection, which can manifest as skin lesions to encephalitis, retinitis, even sepsis. There is a very high transmission rate with vaginal birth. QCCP2,Human herpes viruses

Which of the following amoebae is most commonly the cause of primary amebic encephalitis? A. Entamoeba histolytica B. Acanthamoeba C. Entamoeba coli D. Endolimax nana E. Naegleria fowleri

E. N. fowleri infection is associated with fresh water exposure. The organism migrates through the nasopharynx and invades the brain through the cribriform sinus. Often there is a history of trauma in fresh water (water skiing accident, diving accident). The infection is especially virulent, often causing death within days. Acanthamoeba can also cause encephalitis, but with a granulomatous appearance. Acanthamoeba is also responsible for the majority of cases of amebic keratitis. QCCP2,Meningitis, specific agents

63. What magnitude elevation of virus-specific IgG titer is usually considered the minimum for the diagnosis of an acute viral infection? A. 2 fold B. 4 fold C. 10 fold D. 100 fold E. 1 million billion fold

B. 4 fold. Paired sera collected 7-10 days apart is used to measure the elevation of IgG titers between convalescence and acute illness. Elevation of 4-fold is considered strong evidence for an acute infection, while a single

122. Which organism causes granulomatous amebic encephalitis? A. Naegleria B. Acanthamoeba C. Entamoeba histolytica D. Entamoeba hartmanii E. Iodamoeba

B. A . Acanthamoeba is known for causing GAE as well as a severe keratitis in contact lens users who make their own contact lens cleaning solution or use tap water. QCCP2, Acanthamoeba

141. Which nematode has a characteristic mammilated bile-stained egg? A. Trichuris B. Ascaris C. Necator D. Ancylostoma E. Strongyloides

B. A. Without the unique outer shell, Ascaris eggs resemble those of hookworms or Strongyloides. Ascaris is also significant for its lifecycle - eggs are ingested, hatch in the intestine, migrate to the lungs, and, after being expectorated, are in turn swallowed and take up residence in the duodenum. During the lung stage, they can cause the hypereosinophilic Loeffler syndrome. QCCP2, Ascaris

What is the causative agent of visceral larva migrans? A. Ancylostoma brazilensis B. Loa loa C. Toxicara canis D. Francisella tularensis E. Chlamydia trachomatis

A. Ancylostoma is the causative agent of cutaneous larval migrans, while Loa loa inhabits the subcutis and conjunctiva. Francisella tularensis causes ulceroglandular fever. Chlamydia trachomatis causes lymphogranuloma venereum and trachoma. QCCP2,T3.2

137. Extraerythrocytic ring forms are characteristic of which organisms? A. Babesia microti B. Plasmodium falciparum C. Plasmodium vivax D. Plasmodium ovale E. Plasmodium malariae A.

A. B . Only Babesia has extraerythrocytic forms. In addition, there aren't gametocytes or schizonts present in the peripheral blood with babesiosis. QCCP2, Babesia microti

123. What is the non-pathogenic flagellate that must be distinguished from Giardia lamblia? A. Chilomastix mesneli B. Dientamoeba fragilis C. Trichomonas vaginalis D. Trypanosoma cruzi E. Leishmania donovani

A. C . Unlike the "falling leaf" motility of Giardia, C. mesneli has a rotary motion and a cyst form with only one nucleus (Giardia cysts have 4. The other choices are all pathogenic organisms. , QCCP2, Chilomastix mesneli

111. All of the following are endemic areas for the human T cell lymphotropic virus - I, except: A. Norway B. Caribbean C. S. Japan D. Brazil E. S. Africa

A. Norway. HTLV-I is spread primarily through IV drug use and sexual contact. It is the causative agent of the demyelinating disease, tropical spastic paraparesis and adult T cell lymphoma through the infection of CD4+ T cells. QCCP2,HTLV-I

69. In which of the following patient populations is the risk of CMV retinitis, encephalitis, or nephritis at its highest? A. HIV patients with a CD4 counts <100/mL B. HIV patients with CD4 counts between 500 and 1000/mL C. solid-organ transplant recipients D. older children E. elderly adults

A. HIV patients with CD4 counts <100/mL. In addition to HIV patients with very low CD4 counts, immunocompromised transplant recipients are at an increased risk, though not as great as that of HIV patients. Typically, primary CMV presents with a mononucleosis-like syndrome, which can progress to a pneumonia - especially in neonates and the immunocompromised. QCCP2,CMV

79. What's the best definition of heterophile antibodies as produced in EBV infections? A. IgM antibodies with an affinity for sheep and horse red blood cells B. IgM antibodies with an affinity for the capsule of all DNA viruses C. IgA antibodies directed against protein-antigens often consumed in a normal diet D. IgG antibodies secreted in tears with an affinity pigeon egg antigens E. IgG antibodies with an affinity for plant antigens

A. IgM antibodies with an affinity for sheep and horse red blood cells. Heterophile antibodies are a fairly specific, though not very sensitive indicator of EBV infection. They are also the basis of the Monospot EBV detection agglutination assay. QCCP2,EBV

All of the following organisms utilize the mosquito as a vector, except: A. Loa loa B. Wuchereria bancrofti C. Brugia malayi D. Dirofilaria immitis E. Plasmodium falciparum

A. Loa loa is spread by the mango fly (Chrysops). There are a few memorable and significant vector-organism pairs to remember. Lyme disease, ehrlichiosis, and babesiosis are spread by the Ixodes tick. Borrelia recurrentis is the only borrelial species spread by a louse (the human body louse) rather than a tick. Trypanosoma cruzi and the reduviid bug, Leishmania (cutaneous) and the sandfly (Phlebotomus), and Onchocerca and the black fly (Simulium) are all high-yield. QCCP2,T3.3, Vectors

134. Individuals who lack the Duffy antigen on the surfaces of their red blood cells are protected against which species of Plasmodium? A. P. vivax B. P. falciparum C. P. malariae D. A & B E. A, B, C

A. P. . The Duffy antigen is the receptor for P. vivax; therefore, loss of the receptor affords some protection against infection. G6PD deficiency provides some protection against all species of Plasmodium, while sickle cell trait protects individuals predominantly against P. falciparum. QCCP2, Plasmodium

140. Which nematode has a characteristic double-operculated egg? A. Trichuris trichuria B. Ascaris lumbricoides C. Necator americanus D. Ancylostoma duodenale E. Strongyloides stercoralis

A. T. Trichuris, the whipworm, has an extremely tapered anterior end and double-operculated egg. It may coinfect with Ascaris. QCCP2, Trichuris

100. Which of the following tests for influenza is considered the gold standard? A. culture B. direct fluorescent antibody C. detection of influenza RNA D. serology E. rapid Monospot

A. culture. Nasopharyngeal, sputum, or throat samples can be used to culture virus, either in cell culture or in the more rapid shell vial assay. All the other tests mentioned, with the exception of the Monospot test, have shown utility in the diagnosis of influenza. QCCP2,Orthomyxovirus, diagnosis

66. How can herpes simplex virus definitively be identified in shell vial assay? A. direct fluorescent antibody stain B. cytopathic effect viewed with light microscopy C. reculture (shell vial assay as a starter culture) D. A & B E. A, B, C

A. direct fluorescent antibody stain. The shell vial technique is very popular in virus labs due to its small size, low volume, ease of use, and ability to run multiple samples in parallel. The assay involves centrifugation of the patient sample onto a cover slip coated with a culture monolayer. In a shell vial assay for HSV, cytopathic effect is NOT used as indication of a positive assay, but rather the detection of viral antigens by direct fluorescent antibody staining. QCCP2,Human herpes virus

All of the following criteria are used in the diagnosis of prosthetic joint infection, except: A. joint pain with positive bacteremia in two successive blood cultures B. growth of the same microorganism in two or more synovial fluid or periprosthetic tissue cultures C. purulent synovial fluid or periprosthetic tissue D. acute inflammation in periprosthetic tissue E. presence of a sinus tract

A. joint pain with positive bacteremia in 2 successive blood cultures. Each of the applicable criteria is fairly specific for prosthetic joint infection. There are several etiologies of joint infection. The most common is the direct introduction of bacteria, though in a small percentage of late infection, hematogenous spread is the cause. QCCP2,Prosthetic joint infection and other clinical syndromes

113. Which test is the primary screening test for HIV? A. serum enzyme-linked immunosorbent assay B. Western blot C. quantitative HIV RNA D. CD4 count E. p24 antigen detection

A. serum enzyme-linked immunosorbent assay. The extremely high sensitivity of the serum ELISA test makes it the screening test of choice. There can be a window period between the infection and seroconversion, usually 6-8 weeks, leading to possible false negative results. The confirmation of a positive result is usually done with Western blot, which is read positive if at least two bands (p24, gp41, and gp120/160) are positive. QCCP2,HTLV-3 [HIV-1 and -2]

119. What is the principal means of distinguishing Entamoeba histolytica from Entamoeba hartmanii by light microscopy? A. size of trophozoite B. appearance of karyosome C. appearance of nuclear chromatin D. number of nuclei in cyst form E. appearance of chromatoidal bars in cyst

A. size of trophozoite. The only selection that is different between the related organisms is the size of the trophozoite. Entamoeba histolytica is roughly twice the size at 20-30 microns diameter than E. hartmanii, which is only 5-10 microns in diameter. Also, though non-specific, E. histolytica tends to be the most common trophozoite to contain ingested RBCs. QCCP2,T3.16, Amoeba that resemble E. histolytica

106. What does hantavirus and the Crimean-Congo hemorrhagic fever viruses have in common? A. they are members of the bunyavirus family B. they are arthropod-borne C. they are found in geographically overlapping areas D. they have extremely long latency E. they have DNA-based genomes

A. they are member of the bunyavirus family. Hantavirus and the Congo-Crimean hemorrhagic fever virus are both members of the bunyavirus family, along with other hemorrhagic fever viruses, such as Rift Valley fever and La Crosse viruses. Most other hemorrhagic fever viruses belong to other virus families, such as the filoviruses Marburg and Ebola. QCCP2, Family Bunyaviridae

139. Which of the following is the most common AIDS-defining illness? A. cryptosporidiosis B. Pneumocystis pneumonia C. esophageal candidiasis D. Kaposi sarcoma E. toxoplasmosis

B. P pneumonia. PCP, or Pneumocystis carinii pneumonia, is the most common AIDS-defining illness. Now renamed Pneumocystis jiroveckii, the organism presents with a characteristic bilateral "bat-wing" distribution of lung opacity with frothy alveolar exudate. Within the exudate, the organisms can be seen either in relief (Wright-Giemsa) or as positivelystaining "crushed ping-pong balls" (GMS). QCCP2, Pneumocystis

104. What is the gold standard assay for the diagnosis of enteroviral meningitis in CSF samples? A. cell culture B. RT-PCR C. direct fluorescent antibody D. EIA E. suckling mouse paralysis assay

B. RT-PCR. As of now, RT-PCR is the most rapid and sensitive assay available for the detection of enterovirus in the CSF. However, backup culture should be done in tandem as well. DFA and EIA are not commonly used, and I just wanted an excuse to use the suckling mouse assay again, which you may recall can be used in the diagnosis of Coxsackie A, an enterovirus. QCCP2,Picornaviruses

What is/are the most common bacterium found in prosthetic joint infections? A. Staphylococcus aureus B. Staphylococcus epidermidis C. Streptococci spp D. gram negative bacilli E. Enterococcus

B. S. epideridis Coagulase-negative staph account for almost 1/2 of the cases of prosthetic joint infections, most often presenting months after surgery. This makes sense since coagnegative staph is a normal skin flora microbe and the majority of joint infections are due to the introduction of bacteria during surgery. On the other hand, since it is normal skin flora, coag-negative staph is a common cause of contamination of cultures. QCCP2,Prosthetic joint infections and other clinical syndromes

125. What feature of Leishmania spp helps to distinguish them from Histoplasmaor Toxoplasma? A. small intracellular amastigotes B. bar-like kinetoplast C. central axostyle D. external flagellum E. extracellular forms

B. bar-like kinetoplast. Especially in the intracellular amastigote forms of the three organisms, the one feature of Leishmania that helps to distinguish it from the others is the bar-like kinetoplast adjacent to the nucleus. Specific culture media, such as Novy-MacNeal-Nicolle medium, can be used to isolate Leishmania where the flagellated promastigote form can be identified. QCCP2, Leishmania

Which feature separates the typeable from non-typeable strains of Haemophilus influenzae? A. HA antigen B. capsule C. mecA gene D. penicillin binding protein E. growth at 42°C

B. capsule. The presence of a capsule separates the typeable (capsulated) from the non-typeable (unencapsulated). Furthermore, the typeable strains are categorized into serotypes according to the type of capsule protein present - the most prevalent serotype being type B. QCCP2,Meningitis, specific agents

MRC-5 cells are an example of which kind of cell culture? A. primary cell culture B. cell line (secondary cell culture) C. established cell line D. human diploid fibroblast E. malignant transformed cell line

B. cell line (secondary cell culture). MRC-5, named for the Medical Research Council where they were first propagated, are a secondary cell line with limited viability. Cells don't survive after a number of transfers, unlike a primary cell culture, which can't be transferred at all, or an established cell line, which can be transferred nearly illimitably. Human diploid fibroblasts are another type of secondary cell culture. QCCP2,Viral lab methods

86. Benign HPV-associated lesions are associated with this form of the virus: A. integrated B. episomal C. mitochondrial D. extracellular E. intralysosomal

B. episomal. In most benign HPV lesions, the virus DNA is maintained in circular extrachromosomal episomes. The process of integration into the host genome by HPV is more often associated with malignant disease. QCCP2,HPV

What is the overall most common cause of bacterial cellulitis? A. coagulase-negative Staphylococcus B. group A Streptococcus C. Pasteurella multocida D. Aeromonas hydrophila E. Vibrio vulnificus

B. group A Strep Coag-negative strep causes many cases of post-traumatic cellulitis; Pasteurella is associated with animal bites, Aeromonas with fresh water and V. vulnificus with salt water exposure. QCCP2,T3.2

120. What is the most common site of extraintestinal amebic abscess? A. lungs B. liver C. brain D. spleen E. bladder

B. liver. The gray-white purulence or anchovy paste amebic abscess is most often in the liver, though the brain and spleen are not uncommon sites for abscess formation. QCCP2, E. histolytica

94. Which of the following scenarios might explain a conflicting set of results in a patient with a positive anti-HCV antibody result and negative HCV RNA PCR? A. no infection B. no infection or recovery from acute HCV C. early HCV D. chronic HCV E. infection

B. no infection or recovery from acute HCV. A positive anti-HCV could be either a false positive, in the case of non-infection, or it could indicate the patient was one of the 15% of cases where HCV did not develop chronic infection. QCCP2,HCV

81. All of the following EBV-associated lesions have demonstrable EBER (EBV-encoded RNA) by in situ hybridization, except: A. Hodgkin lymphoma B. oral hairy leukoplakia C. primary effusion lymphoma D. post-transplant lymphoproliferative disorder E. nasopharyngeal carcinoma

B. oral hairy leukoplakia. In addition to tumors and pre-tumoral lesions, EBER can be shown in the reactive hyperplastic lymphoid tissue of infectious mononucleosis. In some tumors, it is not strongly expressed (~1/2 of Hodgkin disease cases are positive) versus other tumors where it is very strongly expressed (nasopharyngeal carcinoma, NK-T cell lymphoma -nasal type, and endemic-type Burkitt lymphoma). QCCP2,EBV

135. Which form of Plasmodium is described as intraerythrocytic collections of numerous organisms? A. merozoites B. schizonts C. hypnozoites D. trophozoites E. bradyzoites

B. schizonts. The schizont is the form that contains numerous merozoites within the erythrocyte. With the rupture of the schizont, merozoites are released to infect other RBCs. The hemolysis corresponds to the clinical fever spikes. QCCP2, Plasmodium

75. All of the following clinical syndromes are caused by EBV, except: A. infectious mononucleosis B. shingles C. primary effusion lymphoma D. post-transplant lymphoproliferative disease E. oral hairy leukoplakia

B. shingles. Shingles is associated with VZV infection. There are myriad clinical syndromes associated with EBV infection, especially long-term latent effects. In addition to the conditions presented above, primary CNS lymphoma, Burkitt lymphoma, Hodgkin lymphoma, lymphomatoid granulomatosis, and nasopharyngeal carcinoma are all associated with latent EBV infection. QCCP2,T3.9

What's the most common cause of false positive hemadsorption in viral culture? A. Mycoplasma spp B. simian virus C. mycobacterium D. Acanthamoeba E. Candida

B. simian virus. SV is a very common cause of false positive hemabsorption results. An uninoculated control should be run concurrent with the patient sample as a negative control. Another common contaminant is Mycoplasma, which can cause poor growth in cell lines and decreased infective potential of the viruses. QCCP2,Virology, lab methods

91. To what does the "window period" of HBV infection refer? A. the period between the appearance of HBV DNA and infection B. the period between the disappearance of HBsAg and appearance of HBsAb C. the period between the disappearance of HBcAg and appearance of HBcAb D. the period between HBeAg and HBcAg E. the period between infection and IgM anti-HBcAb

B. the period between the disappearance of HBsAg and appearance of HBcAb. Less sensitive assays of the past may have missed the diagnosis of HBV if performed in the brief period around 5-6 months post-infection. Serologically, this corresponds to the period between the disappearance of the surface antigen and the appearance of the surface antibody. Nowadays, we can measure IgM anti-HBc during this time period and expect it to be positive. QCCP2,HBV

129. Where can Cryptosporidium be found in an infected host? A. adherent to small intestinal brush border B. within an intracellular apical vacuole C. interdigitated between enterocytes D. in foveolar gland crypts of the stomach E. intracytoplasmically within enterocytes

B. within an intracellular apical vacuole. On light microscopy, the Cryptosporidia appear to be small (8-15 micron), round organisms attached to the extracellular brush border. However, ultrastructural studies have determined that the organism is located in a unique position within an intracellular, yet extracytoplasmic apical vacuole. Very strange. Isospora interdigitates, Microsporidium is intracellular, and Strongyloides is found within the crypt epithelium. QCCP2,Cryptosporidiosis

99. Which of the following influenza subtypes is associated with pandemic avian influenza? A. H1N1 B. H5N2 C. H5N1 D. H2N1 E. H2N2

C. H5N1. There are currently over 15 H and 9 N subtypes, with the numbers growing steadily due to antigenic shifts. Birds are the more common reservoir for influenza, for example, the chickens in S.E. Asian H5N1 avian influenza. The virus can cause an ARDS clinical appearance with a 50% mortality, predominantly affecting teenagers. QCCP2,Orthomyxoviruses

92. Which HBV antigen has been used to characterize chronic HBV carriers as either replicative or non-replicative? A. HBc B. HBs C. HBe D. HBx E. HBp

C. HBe. In the past, HBe antigen was used to classify patients. However, there are issues with the consistency of HBe serology, so now the measurement of HBV DNA copy number has replaced HBe. A copy number of >105/mL is needed to classify a chronic HBV carrier as "replicative." QCCP2,HBV molecular assays

97. Which of the following hepatitis viruses requires coinfection or chronic infection with HBV in order to infect the liver? A. HAV B. HCV C. HDV D. HEV E. HGV

C. HDV. HDV can only infect hepatocytes that are infected with HBV. Coinfection of patients with HBV and HDV results in a more severe disease and significantly increases the risk of cirrhosis and hepatic failure. QCCP2,HBV

126. Which species of Leishmania is most commonly associated with mucocutaneous leishmaniasis? A. L. major B. L. tropica C. L. brazilensis D. L. donovani E. L. mexicana

C. L. A number of species of Leishmania are pathogenic, often causing distinct disease entities. L. tropica and L. major are associated with solitary cutaneous lesions, while L. donovani is associated with systemic disease (Kala-azar). L. mexicana is the causative agent of the self-limiting Chiclero ulcer of the ear lobe, while L. brazilensis causes mucosal and cutaneous lesions. QCCP2, Leishmania

Which of the following organisms typically causes meningitis in a disproportionate number of both very young and very old patients? A. group B Streptococcus B. Staphylococcus aureus C. Listeria monocytogenes D. Streptococcus pneumoniae E. Haemophilus influenzae

C. L. monocytogenes Besides age (<1 month and older than 70 years), predisposing factors toward the development of Listeria meningitis include diabetes and immunosuppression (steroids, HIV, and transplantation). QCCP2,Meningitis, specific agents

132. Which species of Plasmodium is responsible for quartan (72-hour) fevers? A. P. falciparum B. P. vivax C. P. malariae D. A & B E. A, B, C

C. P. . P. malariae differs from the other species of Plasmodium by having 72 hour or quartan fever spikes rather than the 48 hour tertian fevers. P. malariae can also have nephrotic syndrome and prefers to infect older red blood cells. QCCP2, Plasmodium spp

93. What percentage of people infected with hepatitis C virus will go on to chronic infection? A. <5% B. 25% C. 50% D. 85% E. >99%

D. 85%. The vast majority of people infected with HCV develop chronic infections. Of these, 10-15% become cirrhotic, and of the cirrhotics, 5% (if non-drinkers) will develop hepatocellular carcinoma. Alcohol consumption greatly increases the risk of HCC, especially in the cirrhotic with chronic infection. QCCP2,HCV

62. Which of the following viruses can have both nuclear and cytoplasmic inclusions? A. CMV B. measles C. rabies D. A & B E. A, B, C

D. A & B. Both CMV and measles are known for having nuclear and cytoplasmic inclusions. HSV and adenovirus have nuclear inclusions only, while rabies is the only major human viral pathogen with cytoplasmic inclusions only (Negri bodies). QCCP2,T3.6, Viral histology

83. Which of the following subtypes of herpes virus is a possible cause of roseola infantum (exanthem subitum)? A. HHV6 B. HHV7 C. HHV8 D. A & B E. A, B, C

D. A & B. Both HHV6 and HHV7 cause overlapping and similar clinical syndromes. A small percentage of those infected develop the characteristic roseola infantum rash. In addition, they are both responsible for a significant number of cases of juvenile febrile seizures, presumably due to their tropism for the CNS. QCCP2,HHV6

138. Which of the following organisms is/are commonly seen coinfecting patients with babesiosis? A. Borrelia burgdorfei B. Ehrlichia chaffeensis C. microfilariae D. A & B E. A, B, C

D. A & B. Lyme disease, babesiosis, ehrlichiosis, and even some flaviviruses are transmitted by the deer tick, Ixodes scapularis, on the east coast and the western black-legged tick, Ixodes pacificus, on the west coast. QCCP2, Babesia microti

88. Oral squamous papillomas, laryngeal papillomas, condyloma acuminatum, and low-grade cervical squamous intraepithelial lesions are associated with this/these type/s of HPV: A. HPV6 B. HPV11 C. HPV16 D. A & B E. A, B, C

D. A & B. Subtypes 6 and 11 are often associated with low-grade lesions, while the more oncogenic subtypes, such as 16 and 18, are associated with the higher-grade lesions. HPV18 is most commonly associated with cervical adenocarcinoma. QCCP2,HPV, T3.11

109. Which of the following mosquitoes transmit both yellow fever and Dengue fever viruses? A. Aedes aegypti B. Aedes albopictus C. Culex pipiens D. A & B E. A, B, C

D. A & B. The Aedes mosquitoes are responsible for transmission of the viruses that cause yellow fever and Dengue fever, as well as some of the causative agents of filariasis and viral encephalitis. Culex pipiens is also a vector for many of the Arboviridae, such as Eastern and Western equine encephalitis, but it is not been shown transmit yellow or Dengue fever viruses. QCCP2,Dengue and yellow fever

60. Which of the following viruses is assayed by injection into suckling mice and observation for flaccid paralysis? A. Clostridium botulinum B. adenovirus C. parvovirus D. Coxsackie A virus E. respiratory syncytial virus

D. Coxsackie A virus. Clostridium botulinum can cause flaccid paralysis in infants, but it's not a virus, and it's not assayed in suckling mice. Adenovirus causes cytopathic effect in Hep2 cells, parvovirus needs erythroid precursors and RSV causes syncytia formation in Hep2 cells. QCCP2,T3.5

68. Ramsay-Hunt syndrome is an infection of the facial nerve as caused by which of the following viruses? A. SV40 B. CMV C. HSV D. VZV E. HIV

D. VZV. VZV reactivation in a dermatomal pattern is the cause of the painful shingles rash. When reactivation occurs in the facial nerve the Ramsay-Hunt syndrome can result in facial paralysis, vertigo, tinnitus, and otalgia. QCCP2,VZV

102. What name is given to the characteristic measles-infected cell in the lungs or appendix? A. Anitschow cell B. Touton giant cell C. floret cell D. Warthin-Finkeldey E. Hallmark cell

D. Warthin-Finkeldey cell. The Anitschow cell is seen in rheumatic fever. The Touton giant cell with its wreath-like arrangement of nuclei can be seen with several lesions, including juvenile xanthogranuloma and atypical fibroxanthoma. The floret cell is seen with pleomorphic liposarcoma and the hallmark cell is usually associated with anaplastic large cell lymphoma. QCCP2,Measles

Which of the following viruses grows best in Hep2 cells? A. enterovirus B. Coxsackie A C. Coxsackie B D. adenovirus E. cytomegalovirus

D. adenovirus. Hep2 cells are derived from the upper respiratory tract, a region for which adenovirus has a high tropism (same with RSV). QCCP2,T3.4

131. What test best helps to differentiate pregnant women at a lower risk for intrauterine Toxoplasma infection? A. anti-Toxoplasma IgM B. PCR of CSF C. Giemsa staining D. anti-Toxoplasma IgG E. amniotic fluid serology

D. anti-Toxoplasma IgG. Less than 1/5 of pregnant women have been previously infected by Toxoplasma, a fact which is confirmed with positive IgG anti-toxo serology. These previously infected women are at an extremely low risk of transplacental transmission of Toxoplasma compared to those who have not been previously exposed. QCCP2, Toxoplasma

Which of the following etiologies of meningitis is consistent with CSF findings of glucose <45 mg/dL, protein >500 mg/dL, and a white blood cell count >1000 WBC/mL? A. viral B. amebic C. aseptic D. bacterial E. chemical

D. bacterial. The cause of meningitis can be narrowed down with the CSF chemistry. Low glucose and high protein/WBC count is consistent with a bacterial meningitis. The WBC differential is typically left-shifted with a predominance of neutrophils. QCCP2,Laboratory evaluation

What is the animal reservoir of West Nile virus? A. mice B. rats C. domestic cats D. birds E. rabbits

D. birds. Remember to stay away from dead birds! The host organism is the bird, which passes on the virus through a mosquito vector to humans. Arboviruses in general (to include Eastern equine, St. Louis, California, etc.) are best diagnosed through serological means. QCCP2,Meningitis, specific agents

85. Members of which of the following families of viruses are responsible for progressive multifocal leukoencephalopathy and viral hemorrhagic cystitis? A. herpes viruses B. picornaviruses C. reoviruses D. papovaviruses E. bunyaviruses

D. papovavirus. The papovaviridae are a family of DNA viruses including the papilloma viruses, polyoma viruses, and vacuolating viruses (SV40) JC, a member of the polyoma virus family, is responsible for progressive multifocal leukoencephalopathy, while another polyoma virus, BK, can cause hemorrhagic cystitis. The BK-induced cystitis is notable for the presence of virus-infected "decoy" cells, so named because they can be easily confused for exfoliated high-grade urothelial carcinoma. QCCP2,Papovaviruses

77. All of the following are considered Hoagland criteria for the diagnosis of infectious mononucleosis, except: A. leukocytosis >50% lymphocytes, >10% atypical lymphocytes B. fever C. pharyngitis D. positive culture E. positive serological testing

D. positive culture. Adenopathy is the missing criterion. While positive culture can occur with EBV, it is neither routinely performed, nor required for the diagnosis. These criteria are very restrictive and may miss many cases. Partial fulfillment of criteria can be seen in many other diseases, such as strep pharyngitis, which can have both fever and adenopathy, while the leukocytosis can be seen with CMV or Toxoplasma infections. QCCP2,EBV

121. What's the fastest way to identify Iodamoeba butschlii? A. the presence of ingested red blood cells in the trophozoite form B. culture on a lawn of inactivated E coli C. its small (5-10 micron) size D. the prominent vacuole in the cyst form E. the presence of up to 8 nuclei in the cyst form

D. the prominent vacuole in the cyst form. Iodamoeba beutschlii, at risk of sounding indelicate, has a "butt" or a large clear vacuole in the cyst form. Naegleria is grown on inactivated E. coli, Entamoeba hartmanii is small, and Entamoeba coli has up to 8 nuclei in the cyst form. QCCP2,Protozoa

107. Why are yellow fever and rubella viruses different from the other members of the togavirus family? A. they have DNA genomes B. they have hybrid RNA-DNA genomes C. they require coinfection with another virus D. they do not cause arthropod-borne encephalitis E. they both primarily infect the liver

D. they do not cause arthropod-borne encephalitis. Yellow fever and rubella virus are both RNA virus members of the Togaviridae. Unlike all other togaviruses, such as alphaviruses and other flaviviruses, they are not predominantly arthropod-borne causes of encephalitis. Yellow fever favors the heart, GI tract, liver, and kidneys, while rubella causes lymphadenopathy and rash. QCCP2, Family Togaviridae

95. How is a sustained virological response or a positive HCV treatment outcome defined? A. complete absence of detectable HCV RNA for perpetuity B. disappearance of anti-HCV antibody C. no evidence of chronic HCV on liver biopsy D. undetectable HCV RNA for 24 weeks E. greater than 10-fold reduction in HCV RNA

D. undetectable HCV RNA for 24 weeks. A sustained virologic response (SVR) is used to define patients who have responded positively to treatment (IFN/ribavirin). The single most important prognostic predictor of response to IFNs is the genotype of HCV. Types 2 and 3 respond well while type 1, the more common type seen in the U.S., tends to respond poorly. QCCP2,HCV

Patients with complement deficiencies are at an increased risk for meningitis caused by this infectious agent: A. Streptococcus pneumoniae B. Haemophilus influenzae C. E. coli D. Listeria monocytogenes E. Neisseria meningitidis

E. N. meningitidis is associated with outbreaks of meningitis in children and adults in close living conditions, such as schools, dorms, barracks, or nursing homes (though less prevalent in the elderly). Systemic meningococcemia is associated with a petechial rash and hemorrhagic adrenal infarction (Waterhouse-Friedrichsen syndrome), both of which have a poor prognosis. QCCP2,Meningitis, specific agents

118. Which parasite can be specifically detected serologically after a recent infection? A. Paragonimus westermanii B. Strongyloides stercoralis C. Brugia malayi D. Taenia solium E. Toxoplasma gondii

E. T. For the most part, specific serology beyond elevated IgE following parasitic infection is not available. The exception is Toxoplasma, which is a potentially catastrophic cause of transplacental (the "T" in TORCH) infection if it is primarily acquired by a woman during pregnancy. QCCP2,Laboratory methods

76. Which of the following disorders, also known as Duncan disease, is characterized by hepatic necrosis with a profound NK/T cell infiltrate? A. Reye syndrome B. immunoreactive cirrhosis C. hepatitis mononucleosis D. primary hepatic lymphoma E. X-linked lymphoproliferative disorder

E. X-linked lymphoproliferative disorder. As an X-linked disorder, primarily men are affected. The range that disease can manifest extends from the previously mentioned hepatic necrosis and death to less severe agammaglobulinemia or B-cell lymphoma. The disorder is due to a defect in the SAP gene, which leads to uncontrolled NK/T cell activation. QCCP2,EBV

87. Which disease is associated with an inherited defect in the ability to defend against several HPV subtypes? A. Li-Fraumeni B. recurrent respiratory papillomatosis C. progressive multifocal leukoencephalopathy D. post-transplant lymphoproliferative disorder E. epidermodysplasia verruciformis

E. epidermodysplasia verruciformis. An autosomal recessive condition mapped to a gene on chromosome 17, EV manifests with upper extremity lesions within the first 10 years, which can progress to invasive squamous cell carcinoma. QCCP2,HPV

108. All of the following are potential consequences of in utero rubella infection, except: A. glaucoma B. congenital heart disease C. sensorineural deafness D. microcephaly E. midzonal hepatic necrosis

E. midzonal hepatic necrosis. Congenital rubella is a potentially devastating infection, especially if acquired in the first trimester. While hepatosplenomegaly can occur, midzonal necrosis is not seen. It is, however, a prominent feature of yellow fever infection. QCCP2,Rubella virus

105. What is notable about the culture of rhinovirus? A. several weeks of incubation B. culture must contain support virus C. high salt media is needed D. requires addition of nasal mucus to culture E. must be incubated at 32°C

E. must be incubated at 32°C. The only unique property of rhinovirus is that it should be cultured in a temperature slightly lower than body temperature. The thought of adding nasal mucus to a culture is a little more than I can bear. QCCP2,Rhinovirus

103. This virus is responsible for nearly all cases of infantile respiratory bronchiolitis: A. parainfluenza virus B. influenza A virus C. metapneumovirus D. Coxsackie A virus E. respiratory syncytial virus

E. respiratory syncytial virus. Respiratory syncytial virus also causes 1/2 of all cases of lower respiratory tract infections in children. Persistence of immunity does not often occur, so reinfection is common. Among other techniques, the characteristic formation of syncytia in Hep-2 cells is used in the diagnosis of RSV. QCCP2,RSV