MOD6 (LIR) MICRO
E
10.1 A diagnosis of diphtheria is confirmed by: A. microscopic appearance of organisms stained with methylene blue. B. isolation of a typical colony on Tinsdale agar. C. isolation of typical organisms from materials such as blood, showing invasiveness. D. detection of β phage plaques in cultures of suspi cious isolates. E. demonstration of toxin production by a suspicious isolate.
A
10.2 Listeria monocytogenes shows which of the following characteristics? A. It can grow at refrigerator temperatures (4°C). B. It is an extracellular pathogen. C. It is catalase negative. D. It is a gram-negative coccus. E. It is strictly a human pathogen.
B
10.3 A 26-year-old woman, 8 months pregnant, visits her obstetrician complaining of fever, myalagia and back ache of recent onset. Three weeks earlier, the patient had been a weekend guest at a rural farmhouse, where all the food was reported to be "unprocessed" and "natural." A culture of the patient's blood shows gram-positive rods that are catalase positive and dis play a distinctive tumbling motility in liquid medium. What is the most likely source of the woman's infec tion? A. Well-done roast beef B. Fresh, raw cow's milk C. Home-baked bread D. Homemade applesauce E. Baked apple pie
E
10.4 A 45-year-old cattle rancher presents to his physician with a wound on his forearm that resembles a large scab. Samples collected from the wound were cul tured and examined. The bacteria recovered were Gram positive, nonmotile rods with square ends. The cultured bacteria formed irregularly shaped, non hemolytic colonies on blood agar plates and individual cells from the plates had a centrally located spore. What is the most likely cause of this infection? A. Listeria monocytogenes B. Staphylococcus aureus C. Legionella pneumophila D. Corynebacterium diphtheriae E. Bacillus anthracis
B
25.2 The histological presentation typical of infectious mononucleosis caused by Epstein-Barr virus is due to: A. stimulation of B-cell proliferation by the Epstein Barr virus early proteins synthesized in the infected cells. B. proliferation of cytotoxic T cells responding to Epstein-Barr virus antigens expressed on the sur face of infected B cells. C. a primary humoral immune response to the Epstein-Barr virus infection. D. macrophages responding to the death of Epstein Barr virus-infected cells. E. activation of an oncogene resulting from a chromo some translocation in Epstein-Barr virus-infected lymphocytes.
C
25.3 Acyclovir is largely ineffective in the treatment of human cytomegalovirus infections because: A. human cytomegalovirus exhibits a high rate of mutation in the target enzyme. B. human cytomegalovirus depends upon the host cell's DNA polymerase for replication of its DNA. C. human cytomegalovirus lacks the thymidine kinase required for activation of acyclovir. D. the tissues in which human cytomegalovirus multi plies are largely inaccessible to the drug. E. human cytomegalovirus codes for an enzyme that inactivates the drug.
D
26.1 Killing of liver cells infected with hepatitis B virus is primarily caused by: A. shut-off of cellular protein synthesis. B. intracytoplasmic accumulation of hepatitis B virus antigen aggregates. C. degradation of cellular mRNA. D. attack by cytotoxic T lymphocytes directed against hepatitis B virus antigens. E. virus-induced aberrant chromosome rearrange ments and deletions.
B
26.2 The most common natural mode of transmission of infection with hepatitis B virus is via: A. contaminated water supply. B. body fluids, such as urine and semen. C. respiratory droplets. D. direct contact. E. infected insect vectors.
A
26.3 Hepatitis delta virus is unique in that: A. infectivity requires an envelope protein provided by a helper virus. B. it has an RNA genome that is replicated by a repli case supplied by a coinfecting helper virus. C. its mRNA is transcribed by a transcriptase sup plied by a helper virus. D. the virion contains a reverse transcriptase pro vided by a helper virus. E. it encodes a protein delta antigen (HDAg) that replaces helper virus glycoproteins in the envelopes of helper virus particles.
A
26.4 A patient suffering from hepatitis underwent a battery of laboratory tests to determine the cause of the dis ease. The following results were obtained from sero logical and biochemical testing of the patients serum: HBsAg positive, HBeAg positive, anti-HBcAg IgM positive, anti-HBsAg negative, HDV RNA negative, elevated liver enzymes. From these results, how would you diagnose this patient's infection? A. Acute hepatitis B disease B. Chronic hepatitis B disease C. Chronic hepatitis B disease with hepatitis D super infection D. Acute hepatitis D disease E. Chronic hepatitis D disease
B
15.3 A distinctive feature of spirochetes is the presence of: A. fimbriae. B. endoflagella. C. helically arranged pili. D. nucleosomes. E. variable surface antigens.
B
15.4 Syphilis and Lyme disease are strikingly similar in which of the following aspects? A. Their modes of transmission are similar. B. Both diseases display three similar, distinct phases. C. Both causative agents share many antigenic markers. D. The diseases show cross-immunity. E. Both causative agents can be cultured.
D
15.5 A 22-year-old male presents to his physician, com plaining of a 2-week history of a sore on his penis. Physical examination shows a firm, raised, red, non tender chancre midway between the base and glans. Which of the following is the most appropriate course of action for the physician? A. Test a serum sample for antibodies to herpes sim plex virus. B. Swab the chancre and culture on Thayer-Martin agar. C. Swab the chancre and perform a Gram stain. D. Perform a dark-field examination on a swab of the active lesion. E. Swab the chancre and culture on blood agar.
C
15.6 A 13-year-old boy, previously healthy, developed flu like symptoms including fever and malaise. These constitutional symptoms were accompanied by a spreading, circular rash on the child's back. Travel and recreational history indicated that the boy had recently been camping in rural Connecticut. The boy was unaware of any abrasions, bites, or other injury. Which of the following characteristics is unique to the organ ism that is the most likely cause of this infection? A. The outer membrane contains lipopolysaccharide. B. The outer surface is composed of mycolic acids. C. The genome is composed of one linear chromo some and a series of circular and linear plasmids. D. The disease is caused by elaboration of a potent exotoxin. E. The disease is transmitted by the bite of a body louse.
A
16.1 Postpartum fever due to Mycoplasma hominis is treated with: A. tetracycline. B. erythromycin. C. penicillin G. D. a second-generation cephalosporin. E. vancomycin.
B
16.2 A distinguishing feature of human Mycoplasma species is that they: A. stain well with Giemsa but not by Gram stain. B. contain no bacterial peptidoglycan. C. are not immunogenic because they mimic host cell membrane components. D. cannot be cultivated in vitro. E. are dependent on host sources of adenosine triphosphate.
B
16.3 Which of the following is most characteristic of Mycoplasma pneumoniae infection? A. Infection results in a fever of sudden onset accompanied by a productive cough. B. Infection most commonly occurs in the upper respiratory tract. C. Infection is definitively diagnosed by direct microscopic examination of sputum. D. Reinfection is rare and less severe than primary infection. E. Infection causes extensive scarring and calcification of affected lung tissue.
E
16.4 A 30-year-old woman complained of unrelenting headache, accompanied by fever, chills, and malaise. After 2 to 4 days, a dry cough developed. Chest X-rays reveal a patchy, diffuse bronchopneumonia involving both lobes. Her white cell count was normal. Which of the following is the most likely diagnosis? A. Legionellosis B. Infection with parainfluenza virus C. Infection with Streptococcus pneumoniae D. Infection with Haemophilus influenzae E. Infection with Mycoplasma pneumoniae
B
17.1 Which one of the following is characteristic of chlamydiae? A. Reticulate bodies are an infectious, extracellular form of the organism. B. Most genital tract infections are asymptomatic and undiagnosed and untreated. C. They are sensitive to β-lactam antibiotics. D. They stain gram-positive. E. Inclusion bodies are formed from division of elementary bodies
B
17.2 A feature of chlamydiae that is unique to this group is: A. the requirement of an obligate intracellular habitat. B. its replicative cycle is distinguished by two morphologic forms that develop within cytoplasmic vacuoles. C. the lack of detectable peptidoglycan in its cell envelope. D. its use of host coenzymes of energy metabolism. E. all of the above.
D
17.3 A 19-year old male presents at an STD clinic with a urethral discharge and dysuria. A swab specimen was collected and examined by Gram stain followed by light microscopy. Polymorphonuclear leukocytes were detected in the exudate along with intracellular and extracellular Gram negative diplococci. How should this patient's infection be treated? A. No treatment is necessary B. With a tetracycline-based antibiotic such as doxycycline. C. With a third-generation cephalosporin antibiotic such as ceftriaxone D. With a combination of ceftriaxone and doxycycine E. With penicillin
B
17.4 A 35-year-old, small animal veterinarian presents with severe headache, myalgia, and splenomegaly in addition to pulmonary findings. A scanty sputum was obtained, containing a few mixed bacteria and scattered mononuclear cells on routine Gram staining. Which of the following organism is most likely to caause these symptoms? A. Chlamydophila pneumoniae B. Chlamydophila psittaci C. Chlamydia trachomatis D. Legionella pneumophila E. Mycoplasma pneumoniae
E
17.5 Which of the following antibiotics is most likely to be effective for chlamydial infections? A. Penicillins B. Vancomycin C. Cephalosporins D. Carbapenems E Macrolides
A
18.1 Which one of the following is characteristic of mycobacteria? A. They contain mycolic acids. B. They are resistant to inactivation by heat. C. They grow extracellularly. D. They are anaerobic. E. They are spore forming.
E
18.2 An acid-fast smear on a patient's sputum is positive. The tuberculin test, however, is negative. A more definitive diagnosis could be obtained by A. paying attention to the patient's history. B. a more extensive physical examination. C. a chest radiograph. D. repeat of the sputum smear. E. laboratory culture and speciation.
A
18.3 Which of the following statements regarding Actinomyces and Nocardia is true? A. Both organisms have branching growth but are prokaryotes. B. Neither can be cultured in the laboratory C. Nocardia infections are endogenous and often initiated by trauma. D. Actinomyces usually causes infections in systemically compromised patients. E. Neither is sensitive to antibacterial drugs.
E
18.4 The treatment of tuberculosis A. is initiated with a single "first-line" drug. B. is initiated after the results of sensitivity testing is available. C. is most effective in patients with chronic or arrested tubercles. D. may last 2 to 3 weeks. E. should be directly observed whenever possible.
C
18.5 Virulence in mycobacteria is most strongly correlated with: A. mycotoxin production. B. slow growth. C. composition of the cell envelope. D. small size of cells. E. dependence on oxygen for growth.
E
19.1 Pathogens in the genus Rickettsia: A. grow only extracellularly. B. have eukaryotic-type cell organization. C. cause contagious infections because they are disseminated by respiratory droplets. D. are clinically sensitive to penicillin. E. generally invade the endothelial lining of capillaries, causing small hemorrhages.
D
19.2 The vector of Rocky Mountain spotted fever is the: A. human body louse. B. rat flea. C. deer tick. D. dog tick. E. mosquito.
A
19.3 Ehrlichiosis and Rocky Mountain spotted fever have all but which of the following clinical features in common? A. Both involve parasitized blood cells. B. Both are acute fevers. C. Both are transmitted by the same vector. D. Both can be treated by doxycycline. E. Both are potentially lethal.
C
19.4 Coxiella burnetii: A. cannot survive outside its host. B. has no reservoir other than humans. C. causes a pneumonitis called Q fever. D. causes symptomatic disease only in the lower respiratory tract. E. is found only in the United States.
C
19.5 A 14-year-old male presents to the emergency room in North Carolina with fever and a distinctive rash on his extremities. The rash is most prominent on the palms of his hands, but has spread to his lower arms as well. The patient was well before a camping trip 1 week prior to symptom onset. Which of the following bacterial pathogens is the most likely causative agent of this disease? A. Coxiella burnetii B. Ehrlichia chaffeensis C. Rickettsia rickettsii D. Anaplasma phagocytophilum E. Rickettsia prowazekii
B
2.1 The primary effect of lactobacilli in the adult vagina is to A. maintain an alkaline environment. B. maintain an acidic environment. C. produce a protective mucus layer. D. increase fertility. E. keep the menstrual cycle regular.
D
2.2 A patient presents with severe colitis associated with an overgrowth of Clostridium difficile in the lower bowel. The most likely cause of this condition is A. botulinum food poisoning. B. a stomach ulcer. C. a compromised immune system. D. antibiotic therapy. E. mechanical blockage of the large intestine.
D
2.3 The predominant bacterial species that colonizes the human skin is A. Lactobacillus. B. Candida albicans. C. Streptococcus pneumoniae. D. Staphylococcus epidermidis. E. Bacterioides fragilis.
C
20.1 A component of the cell membrane of most fungi is: A. cholesterol. B. chitin. C. ergosterol. D. peptidoglycan. E. keratin.
C
20.2 A physician visiting a rural Latin American village finds that many mature males but few immature males or females of any age are afflicted by a particular fungal disease. What is likely to be the diagnosis? A. Mycetoma B. Blastomycosis C. Paracoccidioidomycosis D. Mucormycosis E. Histoplasmosis
C
20.3 A fungus that can attack hair is: A. Trichophyton. B. Rhizopus. C. Microsporum. D. Sporothrix. E. Epidermophyton.
B
20.4 A farmer in Mississippi presents with a chronic cough. Chest radiograph reveals an opaque mass, and biopsy of the lung shows macrophages with multiple yeast forms. Which one of the following diagnoses is most likely? A. Coccidioidomycosis B. Histoplasmosis C. Blastomycosis D. Paracoccidioidomycosis E. Sporotrichosis
C
21.1 The protozoal trophozoite phase is characterized by: A. metabolic dormancy. B. toxin production. C. active feeding and reproduction. D. flagellar locomotion. E. residence in the intermediate host.
B
21.2 The definitive host of a parasite is the host: A. in which asexual reproduction occurs. B. in which sexual reproduction occurs. C. that is obligatory for the parasite. D. that is capable of destroying the parasite. E. that is the vector organism that transports a para site from an uninfected to an infected host.
B
21.3 Plasmodium falciparum, which causes malaria, is an example of: A. an ameboid protozoan. B. a sporozoan. C. a flagellate. D. a ciliate. E. a schizont.
D
21.4 A U.S. businessman who has recently returned home from Haiti suddenly develops a periodic high fever followed by orthostatic hypotension. What is the likely preliminary diagnosis? A. Chagas disease B. Giardiasis C. Syphilis D. Malaria E. Toxoplasmosis
E
21.5 A 22 year old female visits her gynecologist com plaining of a foul-smelling vaginal discharge and severe itching. A specimen was collected and exam ined it by light microscopy revealing highly motile, nucleated cells with multiple flagella. What is the most likely causative agent of this infection? A. Balantidium coli B. Plasmodium falciparum C. Toxoplasma gondii D. Giardia lamblia
C
22.1 A patient is diagnosed as having a trematode infec tion. Lacking a more specific identification of the causative organism, which of the following drugs would most likely be effective? A. Niclosamide B. Thiabendazole C. Praziquantel D. Diethylcarbamazine E. Tetracycline
E
22.2 Which of the following is the most common helminthic infection in the United States? A. Schistosomiasis B. Diphyllothriasis C. Clonorchiasis D. Trichinosis E. Enterobiasis
A
22.3 Which of the following helminthic diseases is trans mitted by the bite of a mosquito? A. Filariasis B. Onchocerciasis C. Taeniasis D. Schistosomiasis E. Visceral larva migrans
D
22.4 Which of the following helminthic diseases is trans mitted by direct skin penetration by helminth larvae? A. Filariasis B. Onchocerciasis C. Dracunculiasis D. Schistosomiasis E. Visceral larva migrans
E
23.1 Which one of the following statements concerning the viral replication is correct? A. Most RNA viruses assemble in the nucleus, whereas most DNA viruses develop solely in cytoplasm. B. DNA viruses must provide virtually all enzymatic and regulatory molecules needed for a complete replication cycle. C. Viral (+) single-stranded RNA serves as the tem plate for complementary (-) strand synthesis using host RNA-dependant RNA polymerase. D. In a virus with a single-stranded (ss) RNA genome of (-) polarity, (-) ssRNA is translated into viral proteins. E. In a virus with a double-stranded RNA genome, (+) RNA strands serve both as mRNA and tem plate for complementary (-) RNA strand synthe sis.
E
23.2 The term "eclipse period" refers to: A. the period between epidemic outbreaks of dis eases that occur in a cyclic pattern. B. the period between recurrences of disease in individuals with latent virus infections. C. the time between exposure of an individual to a virus and the first appearance of disease. D. the time between infection of a susceptible cell by a cytocidal virus and the first appearance of cytopathic effects. E. the time between entry into the cell and disas sembly of the parental virus and the appearance of the first progeny virion.
C
23.3 The early genes of DNA viruses code primarily for proteins whose functions are required for: A. transcription of viral mRNA. B. translation of the capsid proteins. C. replication of the viral DNA. D. final uncoating of the infecting virions. E. processing of the mRNA precursors
D
24.1 An important step in the mechanism proposed for oncogenesis by human papillomaviruses is: A. inactivation of a cellular regulatory gene by human papillomavirus integration into the coding region of the gene. B. transactivation of a normally silent cellular onco gene by a human papillomavirus early protein. C. reversal of keratinocyte differentiation caused by continued active replication and production of progeny human papillomavirus. D. specific binding of certain human papillomavirus early proteins to cellular antioncoproteins. E. induction of a specific chromosome translocation that results in activation of a cellular oncogene.
B
24.2 The characteristic spectrum of diseases caused by autonomous parvoviruses is related to the fact that they: A. integrate into a specific chromosomal site that dis rupts an essential gene and leads to death of the cell. B. require host cells that are actively progressing through the mitotic cycle. C. infect only terminally differentiated cells. D. code for an early protein that shuts off cellular pro tein synthesis. E. increase the severity of the disease normally caused by their associated helper virus.
A
24.3 The characteristic rash of erythema infectiosum is due to: A. virion/antibody immune complex formation. B. bone marrow suppression caused by killing of ery throcyte precursors by B19 infection. C. damage to the liver. D. B19 infection of epithelial cells. E. the inflammatory response to B19 infection of cap illary endothelium.
A
25.1 The initial infection with human cytomegalovirus most commonly occurs: A. during early childhood, by exchange of body fluids. B. in utero, by transplacental transmission from a latently infected pregnant woman. C. by transfer of saliva between young adults. D. by sexual intercourse. E. as a result of blood transfusion or organ transplan tation.
D
29.1 An ornithologist was on a 3-month trip to study sev eral species of birds living in a rain forest in South America. On the 10th day of her trip, she was bitten on the hand by an unusually aggressive bat. The sci entist applied a topical antibiotic ointment and con tinued her research. Four weeks later, the scientist lost feeling in her hand. She shortly began experi encing high fever, periods of rigidity, difficulty in swallowing liquids, drooling, and disorientation. Death followed rapidly. A postmortem biopsy of her brain showed the presence of Negri bodies. These symptoms are consistent with: A. California encephalitis virus. B. Hantaan virus. C. Ebola virus. D. rabies virus. E. lymphocytic choriomeningitis virus.
C
29.2 From 1918 until 1956, the only subtype of influenza observed in humans was H1N1. In 1957, H1N1 was replaced by H2N2. This is an example of: A. viral interference. B. phenotypic mixing. C. antigenic shift. D. antigenic drift. E. viral transformation.
B
3.1 Endotoxin belongs to a class of biological molecules called A. mucopolysaccharides. B. lipopolysaccharides. C. nucleic acids. D. proteins. E. peptidoglycans.
D
3.2 Exotoxins belong to a class of biologic molecules called A. mucopolysaccharides. B. lipopolysaccharides. C. nucleic acids. D. proteins. E. peptidoglycans.
C
3.3 The mechanism of action of diphtheria toxin is to A. disrupt the cell membrane. B. block nucleic acid synthesis. C. block protein synthesis. D. interfere with neurotransmission. E. destroy the cell nucleus.
D
3.4 A 48-year-old woman presented at the emergency room complaining of urinary urgency and flank pain. Microscopic examination of a urine sample revealed gram-negative rods. Prior to initiation of antibiotic therapy, she abruptly developed fever, chills, and delirium. Hypotension and hyperventilation rapidly followed. These observations suggest that the patient is responding to the release of bacterial A. collagenase. B. exotoxin. C. hyaluronidase. D. lipopolysaccharide. E. peptidoglycan
D
30.1 The typical clinical syndrome associated with rotavirus infection is: A. acute gastroenteritis of young adults. B. acute bronchiolitis of infants. C. acute hepatitis. D. nausea, vomiting, and diarrhea in infants and young children. E. acute paralytic syndrome.
C
30.2 Rotaviruses differ from polioviruses in that rotaviruses: A. infect via the fecal-oral route. B. lack an envelope. C. can undergo genetic reassortment. D. do not contain any enzymes. E. have an icosahedral structure.
B
30.3 The diagnosis of a rotavirus infection: A. can be made, in most cases, on the basis of the clinical presentation. B. can be made based upon the detection of viral capsid antigens in stool samples. C. is routinely made by electron microscopy of suit ably treated stool samples. D. can only be made on epidemiologic grounds (for example, if there is an epidemic). E. must be made rapidly so that specific antiviral therapy is initiated as soon as possible.
A
30.4 Appropriate treatment of rotavirus infection includes which of the following? A. Fluid and electrolyte replacement B. Antiviral drugs targeting membrane fusion C. Metronidazole D. Antiviral drugs targeting reverse transcriptase E. Antiviral drugs targeting proteolytic processing
E
31.1 A patient with symptoms of variant Creutzfeldt-Jacob disease caused by eating contaminated beef would most likely exhibit which of the following? A. Circulating antibodies specific for bovine central ner vous system antigens B. DNA copies of the bovine infectious agent integrated into chromosomes of the patient's diseased central nervous system tissue C. Cytotoxic T lymphocytes directed against central ner vous system-specific antigens found in both cattle and humans D. Amyloid deposits that have bovine rather than the human amino acid sequences E. Lack of any bovine-specific protein or nucleic acid or an immune response
B
4.1 Choose the item that correctly matches the microorganism with an appropriate stain or preparation. A. Mycobacterium tuberculosis with India ink B. Fungi with KOH C. Cryptococcus neoformans in cerebrospinal fluid with Ziehl-Neelsen (classic acid-fast stain) D. Chlamydia with Gram stain E. Escherichia coli (gram-negative bacterium) with crystal violet followed by treatment with acetone
D
4.2 Which one of the following media is most suitable for identifying Neisseria gonorrhoeae in a cervical swab? A. Sheep blood agar B. Chocolate agar C. MacConkey agar D. Thayer-Martin medium E. Hektoen enteric agar
B
4.3 A 57-year-old man complains of fever, headache, confusion, aversion to light, and neck rigidity. A presumptive diagnosis of bacterial meningitis is made. Antimicrobial therapy should be initiated after which one of the following occurrences? A. Fever is reduced with antipyretic drugs. B. Samples of blood and cerebrospinal fluid have been taken. C. A Gram stain has been performed. D. The results of antibacterial drug susceptibility tests are available. E. Infecting organism(s) have been identified by the microbiology laboratory.
B
5.1 Which one of the following most correctly describes vaccines containing live, attenuated pathogens? A. Pathogen does not multiply in human hosts. B. They provide extended, sometimes life-long immunity. C. There is no possibility for reversion to pathogenic form. D. They provide little cell-mediated immunity. E. They are administered by injection.
E
5.2 Which one of the following best describes the components of vaccines against Haemophilus influenzae disease? A. Live, attenuated Haemophilus influenzae B. Killed Haemophilus influenzae C. Toxoid derived from Haemophilus influenzae D. Polysaccharide derived from Haemophilus influenzae E. Polysaccharide derived from Haemophilus influenzae conjugated to a protein antigen
D
5.3 Which one of the following best describes the Sabin polio vaccine? A. It provides little gastrointestinal immunity. B. It is prepared with inactive virus. C. It is administered by injection. D. It carries a small risk of causing disease. E. It is an example of passive immunity.
C
5.4 A 25-year-old woman whose blood tested positive for hepatitis B surface antigen gave birth to a full-term child. Which of the following therapies would be most likely to minimize the transmission of hepatitis B to the neonate? A. Administer hepatitis B immunoglobulin. B. Administer hepatitis B vaccine. C. Administer hepatitis B immunoglobulin and hepatitis B vaccine. D. Bottle-feed the neonate.
D
6.1 A bacterial culture with a starting density of 1×103 cells/ml is incubated in liquid nutrient broth. If the bacteria have both a lag time and a generation time of 10 minutes, what will the cell density be at 30 minutes? A. 1.0 × 103 B. 2.0 × 103 C. 3.0 × 103 D. 4.0 × 103 E. 6.0 × 103
E
6.2 Which of the following components are found in the cell walls of gram-positive bacteria but not gram-negative bacteria? A. Cytoplasmic membrane B. Lipopolysaccharide C. Outer membrane D. Peptidoglycan E. Teichoic acid
A
27.1 A company held an elaborate holiday dinner party for its 42 employees. Within 3 to 4 weeks, many of the banquet attendees complained of experiencing fatigue, fever, nausea, and dark urine and were observed to be jaundiced. The group exhibited no bacterial infections in common. The employees who became ill had all eaten raw oysters at the party. The company doctor assayed a sample of the employees' blood for anti-hepatitis B antibodies, but all samples were negative for anti-hepatitis B surface antigen immunoglobulin M. The causative agent consistent with this history is most likely: A. hepatitis A virus. B. hepatitis B virus. C. hepatitis C virus. D. hepatitis D virus. E. hepatitis E virus.
C
27.2 Intravenous drug users are at high risk for the virus. A. Hepatitis A virus B. Coxsackie viruses C. Hepatitis C virus D. Hepatitis E virus E. Yellow fever virus F. Rubella virus
E
27.3 Infection is caused by the bite of an infected mosquito. A. Hepatitis A virus B. Coxsackie viruses C. Hepatitis C virus D. Hepatitis E virus E. Yellow fever virus F. Rubella virus
C
27.4 Infection predisposes to hepatocellular carcinoma. A. Hepatitis A virus B. Coxsackie viruses C. Hepatitis C virus D. Hepatitis E virus E. Yellow fever virus F. Rubella virus
F
27.5 Infection causes congenital malformations. A. Hepatitis A virus B. Coxsackie viruses C. Hepatitis C virus D. Hepatitis E virus E. Yellow fever virus F. Rubella virus
E
27.6 Which of the following groups RNA viruses are com mon causes of viral meningitis? A. Rhinoviruses B. Caliciviruses C. Hepatitis C virus D. Flaviviruses E. Enteroviruses
B
28.1 Current approaches to acquired immune deficiency syndrome therapy involve the use of multiple drugs because: A. it is not known which one will be effective. B. mutants resistant to any one drug appear rapidly, but the chance for appearance of mutants resis tant to all of them is small. C. all inhibit the same step in replication, thereby increasing their effectiveness. D. this is the most effective means of curing cells of integrated human immunodeficiency virus genomes. E. each tends to neutralize the toxicity of the others.
A
28.2 The "asymptomatic period" following the initial acute disease caused by human immunodeficiency virus infection is characterized by: A. high levels of human immunodeficiency virus repli cation in lymphoid tissue. B. high levels of human immunodeficiency virus repli cation in circulating T lymphocytes. C. inability of the immune system to respond to anti genic stimuli. D. absence of detectable human immunodeficiency virus genomes or mRNA in circulating lymphocytes. E. high titers of free virus in the blood.
D
28.3 After infection of a cell by a retrovirus, synthesis of progeny genomes is carried out by: A. the DNA-dependent RNA polymerase activity of viral reverse transcriptase. B. the retrovirus RNA-dependent RNA polymerase. C. the host cell DNA polymerase. D. a host cell RNA polymerase. E. a complex of reverse transcriptase and a second virus protein that enables it to synthesize RNA rather than DNA.
D
28.4 Which one of the following correctly describes human T-cell lymphotropic virus, type 1 (HTLV-1)? A. The majority of infected individuals develop adult T-cell leukemia (ATL) B. HTLV-1 causes myelopathy more frequently than ATL. C. ALT typically appears 2 to 3 years after initial infection. D. Virion entry into lymphocytes occurs most effi ciently by direct cell-to-cell contact, rather than from virions free in plasma. E. HTLV-1 induces death of infected lymphocytes.
A
11.1 A 20-year-old, sexually-active female presents at her family physician's office with fever, painful arthritis of the right knee, and several small pustules on her extremi ties. Material from the pustules and joint fluid were col lected for culture on modified Thayer-Martin medium. Which of the following results are consistent with a diag nosis of gonococcal infection? A. Growth of small colonies consisting of gram-nega tive diplococci. Bacteria grown on plates are cata lase and oxidase positive. B. Growth of small colonies consisting of gram-posi tive cocci. Bacteria growth on plates are catalase and oxidase positive. C. Growth of small colonies consisting of gram-nega tive diplococci. Bacteria growth on plates are cata lase and oxidase negative. D. Growth of large mucoid colonies consisting of gram-negative bacilli. Bacteria growth on plates are catalase and oxidase negative. E. Growth of gram-negative diplococci within polymor phonuclear leukocytes. Bacteria can utilize glucose and maltose as a carbon sources.
D
11.2 Which of the following neisserial virulence factors is subject to high-frequency antigenic variation by a mechanism involving recombination between silent and expressed chromosomal loci? A. Lipooligosaccharide B. Capsule C. Porin D. Pilin E. Opacity proteins
B
11.3 Which of the following neisserial virulence factors is part of the tetravalent vaccine that protects against some but not all serogroups of Neisseria meningitidis? A. Lipooligosaccharide B. Capsule C.Porin D.Pilin E. Opacity proteins
C
12.1 A Lac+, glucose-fermenting, gram-negative rod iso lated from a previously healthy child with bloody diar rhea is most likely to be: A. Shigella sonnei. B. Pseudomonas aeruginosa. C. Escherichia coli. D. Salmonella enterica. E. Helicobacter pylori.
E
12.2 A male older adult, hospitalized and recovering from cardiac bypass surgery, develops pneumonia. Sputum culture reveals a gram-negative rod that produces a green pigment but does not ferment carbohydrates. The most likely organism is: A. Klebsiella pneumoniae. B. Serratia species. C. Proteus species. D. Enterobacter species. E. Pseudomonas aeruginosa.
A
12.3 An older, alcoholic male develops severe, necrotizing lobar pneumonia. The organism is Lac+ and produces a luxuriant capsule. The most likely agent is: A. Klebsiella pneumoniae. B. Serratia species. C. Yersinia pseudotuberculosis. D. Pseudomonas aeruginosa. E. Campylobacter fetus.
C
12.4 A young man returned from a backpacking trip in Mexico suffering from a high fever, pain in the abdomen, and watery diarrhea. The emergency room doctor noted a faint rash on the patient's abdomen and chest. A blood specimen was collected and plated on MacConkey agar, incubated at 37°C in ambient air. Lac- colonies grew on the plates. The cultured organ ism was a gram-negative rod that did not produce Shiga or Shiga-like toxins. The most likely etiological agent for this man's disease is: A. Enterohemorrhagic Escherichia coli B. Shigella dysenteriae C. Salmonella typhi D. Helicobacter pylori E. Campylobacter jejuni
A
13.1 Which of the following is true of Haemophilus influenzae? A. Invasive infections are most commonly associated with encapsulated strains. B. Most invasive infections occur in infants during the neonatal period. C. Most human infections are acquired from domestic pets. D. The organism can be readily cultured on sheep blood agar in an environment of elevated CO2. E. Older adults are rarely at risk for infection with this organism because they typically have a high level of immunity.
C
13.2 For which of the following organisms is there no known animal reservoir? A. Francisella tularensis B. Pasteurella multocida C. Bordetella pertussis D. Brucella melitensis E. Yersinia pestis
B
13.3 Which of the following statements about Bordetella pertussis infection is true? A. Infection causes a leukocytosis characterized pri marily by a marked elevation in polymorphonuclear leukocytes. B. Isolation of the organism from clinical specimens is greatest during the early stages of illness. C. Clinical diagnosis of whooping cough can usually be made within a few days of onset of initial symptoms. D. Children who receive a full series of immunizations with the pertussis vaccine generally develop solid, lifelong immunity to pertussis. E. The organism can be cultured on standard labora tory media such as sheep blood agar.
C
13.4 Which of the following is transmitted to humans via an arthropod vector? A. Pseudomonas aeruginosa B. Legionella pneumophila C. Yersinia pestis D. Brucella abortus E. Pasteurella multocida
A
14.1 The most common form of infection caused by Clostridium botulinum in this country is: A. infant botulism. B. wound infection. C. food poisoning. D. primary septicemia. E. anaerobic cellulitis.
A
14.2 Clostridium perfringens infections are commonly asso ciated with: A. contamination of wounds. B. antibiotic treatment. C. consumption of water contaminated with sewage. D. immunosuppression. E. preexisting lung disease.
B
14.3 Specific antitoxin is an important part of treatment in: A. gas gangrene. B. tetanus. C. necrotic enteritis. D. pseudomembranous colitis. E. Bacteroides and Prevotella infections.
A
14.4 A predisposing factor in pseudomembranous colitis is: A. clindamycin treatment. B. neonatal age. C. diet high in dairy products. D. cholecystitis. E. older age (older than age 60 years).
D
14.5 A 67-year-old man, who is an avid gardener, presents at an emergency department. He is suffering from spastic paralysis, which began in his right hand and now extends to his jaw muscles. The causative agent of this infection produces a virulence factor with which of the following activities? A. Overstimulation of T cells with resulting massive release of cytokines B. Blockage of the release of the neurotransmitter acetylcholine from synaptic vesicles C. Adenosine diphosphate-ribosylation of EF-2, resulting in inhibition of protein synthesis D. Blockage of the release of the inhibitory neuro transmitter glycine E. Glucosylation of Rho-family GTPases
C
15.1 The probable cause for the relapsing nature of relaps ing fever caused by Borrelia recurrentis is: A. the sequential appearance of new antibiotic resis tant variants. B. periodic spore dormancy and activation. C. successive appearance of antigenic variants. D. periodic hormonal fluctuations in the host. E. organisms that survive and propagate after spiro chete-induced fever.
C
15.2 Which of the following spirochete-caused diseases is transmitted by an arthropod? A. Leptospirosis B. Pinta C. Relapsing fever D. Yaws E. Syphilis
C
6.3 In 1998, a large botulism outbreak occurred in El Paso, Texas. The foodborne illness was shown to be caused by foil-wrapped baked potatoes that were held at room temperature for several days before their use in dips at a Greek restaurant. The dip yielded botulinum toxin type A, as did stool and, in some cases serum samples from 18 of the 30 affected patients. Four patients required mechanical ventilation, but none died. What would be the expected outcome if the potatoes had been reheated to 100°C for 10 minutes before being served? [Hint: See pp. 153-154 for properties of Clostridium botulinum toxin.] A. Heat would kill the spores of Clostridium botulinum. B. Heat would promote the vegetative state. C. Heat would inactivate the toxin in the potato dip. D. Heat would increase the number of toxin-producing bacteria. E. Heat would not alter the outcome.
A
7.1 A lysogenic bacterium A. carries a prophage. B. causes lysis of other bacteria on contact. C. cannot support the replication of a virulent phage. D. is often a human pathogen. E. is usually not capable of conjugal genetic transfer.
C
7.2 Which one of the following statements concerning plasmids is true? A. All plasmids can be transfered between bacteria by conjugation. B. Much of the information coded in the plasmid is essential to the survival of the bacteria cell. C. Resistance plasmids carry genes for antibiotic resistance. D. Resistance plasmids cannot be transferred to other bacterial cells. E. Plasmids lack an origin of replication.
E
7.3 What occurs when a temperate bacteriophage enters a state called "lysogeny"? A. Most viral genes are expressed. B. The bacterial cell is lysed. C. Many new viruses are produced. D. Most normal bacterial functions are turned off. E. The virus may become integrated into the host genome.
C
7.4 A virulence factor can be transferred from one strain of bacteria to another in a genetic process that is independent of cell-to-cell contact between the donor and the recipient. Addition of DNase does not interfere with the transfer of the virulence factor either. From these characteristics, which of the following processes is involved in this genetic transfer? A. Conjugation B. Transformation C. Transduction D. Transposition E. Transversion
E
8.1 A 32-year-old woman became ill 4 days after the onset of her menstrual period. She presented in the emer gency room with fever (104°F; normal = 98.6°F), ele vated white blood cell count (16,000/mm3; normal = 4,000 to 10,000/mm3), and an erythematous, sunburn like rash on her trunk and extremities. She complained of fatigue, vomiting, and diarrhea. She had recently eaten at a fast-food restaurant, but otherwise had pre pared all her meals at home. The patient described most likely has: A. staphylococcal food poisoning. B. scalded skin syndrome. C. infection with a Staphylococcus saprophyticus. D. chickenpox. E. toxic shock syndrome.
B
8.2 A 57-year-old man arrives at the emergency room complaining of weakness, fatigue, and intermittent fever that has recurred for several weeks. The patient had a cardiac valvular prosthesis implanted 5 years earlier. Physical examination reveals petechiae (pin point, nonraised, purplish red spots caused by intra dermal hemorrhage) on the chest and stomach. Blood cultures grew catalase-positive, coagulase negative, cocci. The gram-positive organisms failed to ferment mannitol, and their growth was inhibited by novobiocin. What is the most likely infectious agent? A. Staphylococcus aureus B. Staphylococcus epidermidis C. Staphylococcus saprophyticus D. Streptococcus pneumoniae E. Streptococcus agalactiae
E
8.3. An 18-month-old child was brought the pediatrician's office with what appeared to be a sunburn, although the parents denied that the child had been over exposed to the sun. The parents did recall seeing an area of redness and small blisters on the child's arm the night before. Which of the following virulence fac tors is critical to this disease manifestation? A. Toxic shock syndrome toxin. B. Panton-Valentine Leukocidin C. Protein A D. Capsule E. Exfoliatin
C
9.1 Which of the following statements is correct? A. Streptococci are catalase positive. B. Growth of Streptococcus pneumoniae is not sensitive to optochin. C. Streptococcus pyogenes is highly sensitive to bacitracin. D. Streptococci are obligate anaerobes. E. Enterococcus faecalis is β-hemolytic.
B
9.2 A 55-year-old man was admitted to a local hospital with fever and chills. The patient was human immunodeficiency virus positive and had received multiple courses of antibiotics. Blood cultures grew gram-positive cocci, which tested positive with group D streptococcal antisera. The isolate was resistant to penicillin and vancomycin. Which one of the following is the most likely pathogen? A. Streptococcus pneumoniae B. Enterococcus faecium C. Streptococcus pyogenes D. Streptococcus agalactiae E. Streptococcus mutans
A
9.3 A 65-year-old male presents to his family physician with a rapid onset fever, chest pain and cough productive of rusty-yellow sputum. Chest X-ray shows focal lobar infiltrates. A Gram stain of a sputum sample contained many polymorphonuclear leukocytes and extracellular gram-positive diplococci. Capsule-specific antibodies bound to the diplococci resulted in a positive Quellung reaction. Which of the following is the most likely pathogen? A. Streptococcus pneumoniae B. Enterococcus faecium C. Streptococcus pyogenes D. Streptococcus agalactiae E. Enterococcus faecalis