levinson questions

Question 1

clinical cases 22: your patient is a 30 yo woman with facial nerve paralysis. she also has fever and headache but does not have a stiff neck. on physical exam, she has a circular, erythematous, macular rash on the back of her thigh. you suspect that she has lyme disease.

of the following tests, which one is the most appropriate to order to confirm a diagnosis of lyme disease?

A: blood culture to grow the organism
B: stain for inclusion bodies within cells involved in the rash
C: test for serum antibody against the organism
D: darkfield microscopy

Answer 1

C

Question 2

7: each of the following statements concerning endotoxins is correct except:

A: they are less toxic (ie less active on a weight basis) than exotoxins
B: they are more stable on heating than exotoxins
C: they bind to specific cell receptors, whereas exotoxins do not
D: they are part of the bacterial cell wall, whereas exotoxins are not

Answer 2

C

Question 3

15: which one of the following BEST describes the mode of action of endotoxin?

A: degrades lecithin in cell membranes
B: inactivates elongation factor 2
C: blocks release of acetylcholine
D: causes the release of tumor necrosis factor

Answer 3

D

Question 4

25: the effects of endotoxin include each of the following except:

A: opsoinization
B: fever
C: activation of the coagulation cascade
D: hypotenison

Answer 4

A

Question 5

28: each of the following statements concerning exotoxins is correct except:

A: when treated chemically, som exotoxins lose their toxicity and can be used as immunogens in vaccines
B: some exotoxins are capable of causeing disease in purified form, free of any bacteria
C: some exotoxins act in the GI tract to cause diarrhea
D: some exotoxins contain lipopolysaccharides as the toxic component

Answer 5

D

Question 6

32: each of the following statements concerning endotoxins is correct except:

A: the toxicity of endotoxins is due to the lipid portion of the molecule
B: endotoxins are found in most gram-positive bacteria
C: endotoxins are located outside of the cell wall peptidoglycan
D: the antigenicity of somatic (O) antigen is due to repeating oligosaccharides

Answer 6

B

Question 7

64: which one of the following host defense mechanisms is the most important for preventing dysentery caused by salmonella?

A: gastric acid
B: salivary enzymes
C: normal flora of the mouth
D: alpha interferon

Answer 7

A

Question 8

67: which one of the following bacteria has the lowest 50% infectious dose (ID50)?

A: shigella sonnei
B: vibrio cholerae
C: salmonella typhi
D: campylobacter jejuni

Answer 8

A

Question 9

68: for which one of the following enteric illnesses is a chronic carrier state most likely to develop?

A: campylobacter enterocolitis
B: shigella enterocolitis
C: cholera
D: typhoid fever

Answer 9

D

Question 10

83: which one of the following organisms that infects the GI tract is most frequent cause of bacteremia?

A: shigella flexneri
B: campylobacter jejuni
C: vibrio cholerae
D: salmonella typhi

Answer 10

D

Question 11

CC 5: your patient is a 5 yo girl with bloody diarrhea and no vomitting. there is no history of travel outside of san francisco. stool culture grows both lactose-positive and lactose-negative colonies on EMB agar

of the following organisms, which one is most likely to be the cause?

A: shigella sonnei
B: salmonella typhi
C: campylobacter jejuni
D: helicobacter pylori

Answer 11

A

Question 12

CC 47: your patient is a 22 yo man who has been on a low-budget trip to india, where he ate many of the local foods. he has had a low-grade fever, anorexia, and mild abdominal pain for about a month. you suspect that he may have typhoid fever

if he does have typhoid fever, which one of the following is the least likely laboratory finding?

A: culture of the blood reveals gram-negative rods
B: culture of the stool grows lactose-negative colonies in EMB agar
C: his serum contains antibodies that agglutinate salmonella typhi
D: his serum contains antibodies that cause a positive weil-felix reaction

Answer 12

D

Question 13

PE1 14: endotoxin is an important underlying cause of septic shock and death, especially in hospitalized patients. regarding endotoxin, which one of the following is the most accurate?

A: it acts by phosphorylating the G stimulating protein
B: it is a polypeptide with an A-B subunit configuration
C: it induces the synthesis of tumor necrosis factor
D: it is found primarily in gram-positive rods
E: it can be treated with formaldehyde to form an effective toxoid vaccine

Answer 13

C

Question 14

PE2 18: a 70 yo man who is receiving chemotheraphy for leukemia develops a fever to 40 degrees C and has two episodes of teeth-chattering chills, and his blood pressure drops to 80/20 mmHg. Of the following factors, which one is most likely to be the cause of his fever, chills, and hypotension?

A: coagulase
B: dipicolinic acid
C: glycocalyx
D: lipid A
E: mycolic acid
F: pili
G: polysaccharide capsule

Answer 14

D

Question 15

clincial case 19: your patient is a 10 yo girl who has leukemia and is receiving chemo through an indwelling venous catheter. she now has a fever of 39 degrees C but is otherwise asymptomatic. you do a blood culture, and the laboratory reports growth of staphylococcus epidermidis

which one of the following results is least likely to be found by the clinical laboratory?

A: gram-positive cocci in clusters were seen on gram stain of the blood clusters
B: subculture of the blood culture onto blood agar revealed nonhemolytic colonies
C: a coagulase test on the colonies was negative
D: a catalase test on the colonies was negative

Answer 15

D

Question 16

120: which one of the following organisms causes diarrhea by producing an enterotoxin that increases adenylate cyclase activity within enterocytes?

A: escherichia coli
B: bacteroides fragilis
C: staphylococcus aureus
D: enterococcus faecalis

Answer 16

A

Question 17

149: select the one lettered option that is most closely associated with the numbered items.

A: escherichia coli
B: klebsiella pneumoniae
C: salmonella enteritidis
D: proteus mirabilis

is the most common cause of UTI

Answer 17

A

Question 18

CC case 29: your patient is a 40 yo woman with a severe attach of diarrhea that began on the airplane while she was returning from a vacation in the middle east. she has had multiple episodes of watery, nonbloody diarrhea and little vomiting. she is afebrile. a stool culture reveals only lactose-fermenting colonies on EMB agar.

of the following, which one is the most likely cause?

A: shigella sonnei
B: helicobacter pylori
C: escherichia coli
D: pseudomonas aeruginosa

Answer 18

C

Question 19

55: each of the following organisms is an important cause of urinary tract infections except:

A: escherichia coli
B: proteus mirabilis
C: klebsiella pneumoniae
D: bacteroides fragilis

Answer 19

D

Question 20

76: a 65 yo man develops dysuria and hematuria. A gram stain of a urine sample shows gram-negative rods. culture of the urine on EMB agar reveals lactose-negative colonies without evidence of swarming motility. which one of the following organisms is most likely to be the cause of his UTI?

A: enterococcus faecalis
B: pseudomonas aeruginosa
C: proteus vulgaris
D: escherichia coli

Answer 20

B

Question 21

90: each of the following statements concerning gram-negative rods is correct except:

A: escherichia coli is part of the normal flora of the colon; therefore, it does not cause diarrhea
B: E. coli ferments lactose, whereas the enteric pathogens shigella and salmonella do not
C: klebsiella pneumoniae, although a cause of pneumonia, is part of the normal flora of the colon
D: proteus species are highly motile organisms that are found in the human colon and cause UTI

Answer 21

A

Question 22

91: a 70 yo man is found to have a hard mass in his prostate, which is suspected to be a carcinoma. 24 hours after surgical removal of the mass, he develops fever to 39 degrees C and has several shaking chills. of the organisms listed, which one is least likely to be involved?

A: escherichia coli
B: enterococcus faecalis
C: klebsiella pneumoniae
D: legionella pneumophila

Answer 22

D

Question 23

148: select the one lettered option that is most closely associated with the numbered items.

A: escherichia coli
B: klebsiella pneumoniae
C: salmonella enteritidis
D: proteus mirabilis

is frequently implicated in nosocomial infections, is an important cause of community-acquired pneumonia in adults, and has a thick, mucoid capsule

Answer 23

B

Question 24

150: select the one lettered option that is most closely associated with the numbered items.

A: escherichia coli
B: klebsiella pneumoniae
C: salmonella enteritidis
D: proteus mirabilis

pathogenicity associated primarily with UTI; produces utease

Answer 24

D

Question 25

156: select the one lettered option that is most closely associated with the numbered items. A: bacteroides fragilis B: haemophilus influenzae C: pseudomonas aeruginosa D: chlamydia pneumoniae oxidase-positive gram-negative rod that is an important cause of wound and burn infections

Answer 25

C

Question 26

561: select the one lettered option that is most closely associated with the numbered items ``` A: escherichia coli B: shigella sonnei C: salmonella typhi D: salmonella enteritidis E: proteus mirabilis F: pseudomonas aeruginosa G: vibrio cholerae H: campylobacter jejuni I: helicobacter pylori J: bacteroides fragilis ``` causes wound infections with blue-green pus; is oxidase-positive

Answer 26

F

Question 27

case 33: your patient is a 30 yo woman who was part of a tour group visiting a central american country. the day before leaving, several members of the group developed fever, abdominal cramps, and blood diarrhea of the following, which one is the least likely organisms to cause this infection? A: shigella dysenteriae B: salmonella enteritidis C: vibrio cholerae D: campylobacter jejuni

Answer 27

C

Question 28

case 35: your patient is a 28 yo man with 3rd degree burns over a large area of his back and left leg. this morning, he spiked a fever to 40 degrees C and had two teeth-chattering chills. a blood culture grows a gram-negative rod that is oxidase-positive and produces a blue-green pigment of the following, which one is the most likely organism to cause this infection? A: prevotella melaninogenica B: pseudomonas aeruginosa C: proteus mirabilis D: haemophilus influenzae

Answer 28

B

Question 29

case 45: your patient is a 6 yo boy with a history of several episodes of pneumonia. a sweat test revealed an increased amount of chloride, indicating that he has CF. he now has a fever and is coughing up a thick, greenish sputum. a gram stain of the sputum reveals gram-negative rods of the following, which one is the most likely organism to cause this infection? A: pseudomonas aeruginosa B: haemophilus influenzae C: legionella pneumophila D: bordetella pertussis

Answer 29

A

Question 30

PE1 6: a 70 yo woman has sustained 3rd degree burns over a significant area of her body. despite appropriate burn care in the hospital, she spiked a fever of 39 degrees C, and the nurse reports blue-green pus on the dressing covering the burned area. gram stain of the pus reveals gram-negative rods, and antibiotic sensitivity tests show resistance to most antibiotics. which one of the following organisms is most likely to cause this disease? ``` A: nocardia asteroides B: vibrio vulnificus C: vacteroides fragilis D: haemophilus influenzae E: pseudomonas aeruginosa ```

Answer 30

E

Question 31

73: for which one of the following bacterial vaccines are toxic side effects an important concern? A: the vaccine containing pneumococcal polysaccharide B: the vaccine containing killed bordetella pertussis C: the vaccine containing tetanas toxoid D: the vaccine containing diptheria toxoid

Answer 31

B

Question 32

115: each of the following statements concerning certain gram-negative rods is correct except: A: pseudomonas aeruginosa causes wound infections that are characterized by blue-green pus as a result of pyocyanin production B: in unimmunized individuals, invasive disease caused by haemophilus influenzae is most often due to strains possessing a type b polysaccharide capsule C: legionella pneumophila infection is acquired by inhalation of aerosols from environmental water sources D: whooping cough, which is caused by bordetella pertussis, is on the rise because changing antigenicity of the organism has made the vaccine relatively ineffective

Answer 32

D

Question 33

565: select the one lettered option that is most closely associated with the numbered items ``` A: legionella pneumophila B: yersinia pestis C: haemophilus influenzae D: corynebacterium diphtheriae E: pasteurella multocida F: bordetella pertusis G: brucella melitenisis H: listeria monocytogenes I: clostridium perfringens J: neisseria gonorrheoeae ``` gram-negative rod that causes cough and lymphocytosis

Answer 33

F

Question 34

case 2: your patient is a 70 yo man with a long history of smoking who now has a fever and a cough productive of greenish sputum. you suspect pneumonia, and a chest x-ray confirms your suspicion. if a gram stain of the sputum reveals very small gram-negative rods and there is no growth on a blood agar but colonis do grow on chocolate agar supplemented with NAD and heme, which one of the following bacteria is the most likely cause? A: chlamydia pneumoniae B: legionella pneumophila C: mycoplasma pneumoniae D: haemophilus influenzae

Answer 34

D

Question 35

case 31: your patient is a 55 yo woman with a lymphoma who is receiving chemo via IV catheter. she suddenly develops fever, shaking chills, and hypotension of the following, which one is the least likely organisms to cause this infection? A: streptococcus pneumoniae B: klebsiella pneumoniae C: mycoplasma pneumoniae D: proteus mirabilis

Answer 35

C

Question 36

case 20: your patient is a 25 yo woman wiht several purpuric areas indicative of bleeding into the skin. her vital signs are as follows: temperature, 38 degrees C; blood pressure, 70/40; pulse. 140; respiratory rate, 24. you think she has septic shock and do a blood culture which one of the following organisms is least likely to be the cause of her septic shock? A: corynebacterium diphtheriae B: neisseria meningitidis C: clostridium perfringens D: escherichia coli

Answer 36

A

Question 37

33: each of the following statements concerning exotoxins is correct except: A: exotoxins are polypeptides B: exotoxins are more easily inactivated by heat than are endotoxins C: exotoxins are less toxic than the same amount of endotoxins D: exotoxins can be converted to toxoids

Answer 37

C

Question 38

95: which one of the following organisms is most likely to be the cause of pneumonia in an immunocompetent young adult? A: nocardia asteroides B: serratia marcescens C: mycoplasma pneumoniae D: legionella pneumophila

Answer 38

C

Question 39

106: which one of the following types of organisms is not an obligate intracellular parasite and therefore can replicate on bacteriologic media? A: chlamydia B: mycoplasma C: adenovirus D: rickettsia

Answer 39

B

Question 40

114: each of the following statements concerning corynebacterium diphtheriae is correct except: A: C. diphtheriae is a gram-positive rod that does not form spores B: toxin production is dependent on the organism's being lysogenized by a bacteriophage C: diptheria toxoid should not be given to children younger than 3 years because the incidence of complications is too high D: antitoxin should be used to treat patients with diphtheria

Answer 40

C

Question 41

129: which one of the following statements concerning legionella pneumophila is correct? A: it is part of the normal flora of the colon B: it cannot be grown on laboratory media C: it does not have a cell wall D: it causes atyplical pneumonia, especially in those with reduced cell-mediated immunity

Answer 41

D

Question 42

133: each of the following statements concerning pneumonia caused by mycoplasma pneumonia is correct except: A: pneumonia caused by M. pneumonia is associated with a rise in the titer of cold agglutinins B: pneumonia caused by M. pneumonia occurs primarily in immunocompetent individuals C: pneumonia caused by M. pneumoniae is an "atypical" pneumonia D: M. pneumonia cannot be cultured in vitro because it has no cell wall

Answer 42

D

Question 43

139: select the one lettered option that is most closely associated with the numbered items. A: mycobacterium aviumintracellulare B: treponema pallidum C: rickettsia prowazekii D: mycoplasma pneumoniae has no cell wall

Answer 43

D

Question 44

PE1 18: which one of the following answer choices consists of bacteria, both of which produce exotoxins that act by ADP-ribosylation? A: salmonella typhi and vibrio cholerae B: vibrio cholerae and corynebacterium diphtheriae C: salmonella typhi and clostridium perfringens D: corynebacterium diphtheriae and staphylococcus aureus E: clostridium perfringens and streptococcus pyogenes

Answer 44

B

Question 45

PE2 14: disease caused by which one of the following bacteria can be prevented by a toxoid vaccine? ``` A: actinomyces israelii B: bacteroides fragilis C: borrelia burgdorferi D: corynebacterium diphtheriae E: haemophilus influenzae F: listeria monocytogenes G: neisseria meningitidis H: salmonella typhi I: sterptococcus pneumoniae J: yersinia pestis ```

Answer 45

D

Question 46

CC 50: you patient is a 10 yo boy who fell, abraded the skin of his thigh, and developed cellulitis (ie the skin was red, hot, and tender). several days later, the infection was treated with a topical antibiotic ointment, and the cellulitis gradually healed. however, 2 weeks later, he told his mother that his urine was cloudy and reddish, adn she noted that his face was swollen. you suspect acute glomerulonephritis. regarding the causative organisms, what is the most likely appearance of a gram stain of the exudate from the skin infection? A: gram-positive cocci in grapelike clusters B: gram-positive cocci in chains C: gram-positive diplococci D: gram-negative diplococci

Answer 46

B

Question 47

59: which one of the following diseases is best diagnosed by sero-logic means? A: Q-fever B: pulmonary TB C: gonorrhea D: actinomycosis

Answer 47

A

Question 48

70: which one of the following organisms principally infects vascular endothelial cells? A: salmonella typhi B: rickettsia rickettsii C: haemophilus influenzae D: coxiella burnetii

Answer 48

B

Question 49

72: each of the following statements concerning chlamydiae is correct except: A: chlamydiae are strict intracellular parasites because they cannot synthesize sufficient ATP B: chlamydiae possess both DNA and RNA and are bounded by a cell wall C: C. trachomatis has multiple serotypes that can cause different diseases D: most chlamydiae are transmitted by arthropods

Answer 49

D

Question 50

77: a 25 yo man complains of urethral discharge. you perform a gram stain on a specimen of the discharge and see neutrophils but no bacteria. of the organisms listed, the one most likely to cause the discharge is: A: treponema pallidum B: chlamydia trachomatis C: candida albicans D: coxiella burnetii

Answer 50

B

Question 51

96: each of the following statements concerning chlamydial genital tract infections is correct except: A: infection can be diagnosed by finding antichlamydial antibody in a serum specimen B: infection can persist after administration of penicillin C: symptomatic infections can be associated with urethral or cervical discharge containing many polymorphonuclear leukocytes D: there is no vaccine against these infections

Answer 51

A

Question 52

97: which one of the following illnesses is not a zoonosis? A: typhoid fever B: Q fever C: tularemia D: rocky mountain spotted fever

Answer 52

A

Question 53

104: each of the following statements concerning chlamydia trachomatis is correct except: A: it is an important cause of nongonococcal urethritis B: it is the cause of lymphogranuloma venereum C: it is an important cause of subacute bacterial endocarditis D: it is an important cause of conjunctivitis

Answer 53

C

Question 54

108: the soil is the natural habitat for certain microorganisms of medical importance. which one of the following is least likely to reside there? A: clostridium tetani B: mycobacterium aviumitracellulare C: bacillus anthracis D: chlamydia trachomatis

Answer 54

D

Question 55

119: each of the following statements concerning epidemic typhus is correct except: A: the disease is characterized by a rash B: the weil-felix test can aid in diagnosis of the disease C: the disease is caused by a rickettsia D: the causative organisms is transmitted from rodents to humans by a tick

Answer 55

D

Question 56

121: each of the following statements concerning rocky mountain spotted fever is correct except: A: the causative organisms forms beta-hemolytic colonies on blood agar B: headache, fever and rash are characteristic features of the disease C: the disease occurs primarily east of the mississippi D: the disease is caused by a rickettsia

Answer 56

A

Question 57

131: each of the following statements concerning infection with chlamydia psittaci is correct except: A: C. psittaci can be isolated by growth in cell culture and will not grow in blood agar B: the organism appears purple in gram-stained smears of sputum C: the infection is more readily diagnosed by serologic tests than by isolation of the organism D: the infection is more commonly acquired from a nonhuman source than from another human

Answer 57

B

Question 58

135: each of the following statements concerning Q fever is correct except: A: rash is a prominent feature B: it is transmitted by respiratory aerosol C: farm animals are an important reservoir D: it is caused by coxiella burnetii

Answer 58

A

Question 59

137: select the one lettered option that is most closely associated with the numbered items. A: mycobacterium aviumintracellulare B: treponema pallidum C: rickettsia prowazekii D: mycoplasma pneumoniae is an obligate intracellular parasite

Answer 59

C

Question 60

157: select the one lettered option that is most closely associated with the numbered items. A: bacteroides fragilis B: haemophilus influenzae C: pseudomonas aeruginosa D: chlamydia pneumoniae causes atypical pneumonia in immunocompetent adults

Answer 60

D

Question 61

567: select the one lettered option that is most closely associated with the numbered items ``` A: mycobacterium tuberculosis B: borrelia burgdorferi C: nocardia asteroides D: treponema pallidum E: coxiella burnetii F: mycoplasma pneumoniae G: mycobacterium leprae H: chlamydia trachomatis I: rickettsia rickettsii J: leptospira interrogans ``` obligate intracellular parasite that forms elementary bodies

Answer 61

H

Question 62

PE1 31: your patient is a 20 yo man with a urethral discharge. gram stain of the pus reveals many neutrophils but no bacteria. which one of the following organisms is the most likely cause? ``` A: treponema pallidum B: haemophilus ducreyi C: mycobacterium marinum D: candida albicans E: chlamydia trachomatis ```

Answer 62

E

Question 63

PE2 34: regarding chlamydiae, which one of the following is most accurate? A: they are gram-positive rods that do not form spores B: they exhibit swarming motility on a blood agar plate C: their life cycle consists of a metabolically inactive particle in the extracellular phase D: they can replicate only within cells because they lack the ability to produce certain essential mRNAs. E: they replicate in the nucleus of infected cells, where they form inclusions that are useful diagnostically

Answer 63

C

Question 64

CC 13: Ms. jones calls to say that she, her husband, and their child have had nausea and vomitting for the past hour or so. also, they have had some nonbloody diarrhea. you ask when their last meal together was, and she says they had a picnic lunch in the park about 3 hours ago. they have no fever. which one of the following the most likely finding? A: gram stain of the leftover food would show many gram-positive cocci in clusters B: gram stain of the stool would show many gram-negative diplococci C: KOH prep of the leftover food would show many budding yeast D: acid-fast stain of the stool would show many acid-fast rods

Answer 64

A

Question 65

CC 34: your patient is a 40 yo man with a depigmented lesion on his chest that appeared about a month ago. the skin of the lesion is thickened and has lost sensation. he has lived most of his life in rural louisiana. of the following tests, which one is the most appropriate to do to reveal the cause of this disease? A: perform a biopsy of the lesion and do an acid-fast stain B: culture on sabouraud's agar and look for germ tubes C: culture on blood agar anaerobically and do a gram stain D: obtain serum for a weil-felix agglutination test

Answer 65

A

Question 66

99: which one of the following is not an important characteristic of either neisseria gonorrhoeae or neisseria meningitidis? A: polysaccharide capsule B: IgA protease C: M protein D: Pili

Answer 66

C

Question 67

125: each of the following statements concerning gonorrhea is correct except: A: infection in men is more frequently symptomatic than in women B: a presumptive diagnosis can be made by finding gram negative kidney bean-shaped diplococci within neutrophils in a urethral discharge C: the definitive diagnosis can be made by detecting antibodies to neisseria gonorrhoeae in the patient's serum D: gonococcal conjuctivitis of the newborn rarely occurs in the US, because silver nitrate or erythromycin is commonly used as prophylaxis

Answer 67

C

Question 68

128: each of the following statements concerning neisseriae is correct except: A: they are gram-negative diplococci B: the produce IgA protease as a virulence factor C: they are oxidase-positive D: they grow best under anaerobic conditions

Answer 68

D

Question 69

134: each of the followign statements concerning neisseria meningitidis is correct except: A: it is an oxidase-positive, gram-negative diplococcus B: it contains endotoxin in its cell wall C: it produces an exotoxin that stimulates adenylate cyclase D: it has a polysaccharide capsule that is antiphagocytic

Answer 69

C

Question 70

155: select the one lettered option that is most closely associated with the numbered items. A: bacteroides fragilis B: haemophilus influenzae C: pseudomonas aeruginosa D: chlamydia pneumoniae coccobacillary gram-negative rod that causes meningitis in young children

Answer 70

B

Question 71

CC 1 (594): your patient is a 20 yo woman with the sudden onset of fever to 104 degrees F and a severe headache. physical examination reveals nuchal rigidity. you suspect meningitis and do a spinal tap. gram stain of the spinal fluid reveals many neutrophils and many gram-negative diplococci of the following bacteria, which one is most likely to be the cause? A: haemophilus influenzae B: neisseria meningitidis C: sterptococcus pneumoniae D: pseudomonas aeruginosa

Answer 71

B

Question 72

PE1 8: certain microorganisms, such as the protozoan trypanosoma and the bacterium neisseria gonorrhoeae, can change their surface antigens quite frequently. this allows the organisms to evade our host defenses. which one of the following best explains how this frequent change in antigenicity occurs? A: it is due to transposition of existing genes into an active expression site B: it is due to the acquisition of new fertility plasmids by transduction C: it is due to conjugation, during which the recipient obtains new chromosomal genes D: it is due to new mutations that occur at "hot spots" in the genome

Answer 72

A

Question 73

PE2 38: a 20 yo woman presents with a history of vaginal discharge for the past 3 days. on pelvic exam, you see a mucopurulent exudate at the cervical os, and there is tenderness on palpation of the right fallopian tube. you do a gram stain and culture on the cervical discharge. the culture is done on thayer-martin medium, which is a chocolate agar that contains antibiotics that inhibit the growth of normal flora. of the following, which findings are the most likely to be found? A: a gram stain reveals many neutrophils and spirochetes, and culture on thayer-martin medium reveals no colonies B: a gram stain reveals many neutrophils and gram-variable rods, adn culture on thayer-martin medium reveals beta-hemolytic colonies C: a gram stain reveals many neutrophils and gram-negative diplococci, and culture on thayer-martin medium reveals oxidase-positive colonies D: a gram stain reveals many neutrophils but no gram-negative diplococci are seen, and culture on thayer-martin medium reveals coagulase-positive colonies

Answer 73

C

Question 74

case 31: your patient is a 55 yo woman with a lymphoma who is receiving chemo via IV catheter. she suddenly develops fever, shaking chills, and hypotension if a blood culture drawn from the patient described in case 31 grows a gram-negative rod, which one of the following is the least likely organism to cause this infection? A: bordetella pertussis B: escherichia coli C: pseudomonas aeruginosa D: serratia marcescens

Answer 74

A

Question 75

case 31: your patient is a 55 yo woman with a lymphoma who is receiving chemo via IV catheter. she suddenly develops fever, shaking chills, and hypotension of the following virulence factors, which one is the most likely to cause the fever and hypotension seen in the patient? A: pilus B: capsule C: lecithinase D: lipopolysaccharide

Answer 75

D

Question 76

CC 50: you patient is a 10 yo boy who fell, abraded the skin of his thigh, and developed cellulitis (ie the skin was red, hot, and tender). several days later, the infection was treated with a topical antibiotic ointment, and the cellulitis gradually healed. however, 2 weeks later, he told his mother that his urine was cloudy and reddish, adn she noted that his face was swollen. you suspect acute glomerulonephritis. what is the pathogenesis of the cloudy urine and facial swelling? A: toxin-mediated B: direct invasion by the bacteria C: immune complex-mediated D: cell-mediated immunity (delayed hypersensitivity)

Answer 76

C

Question 77

case 20: your patient is a 25 yo woman wiht several purpuric areas indicative of bleeding into the skin. her vital signs are as follows: temperature, 38 degrees C; blood pressure, 70/40; pulse. 140; respiratory rate, 24. you think she has septic shock and do a blood culture of the following mechanisms, which one is least likely to be involved with the pathogenesis of her septic shock? A: increased amount of interleukin-1 B: activation of the alternate pathway of complement C: increased amount of tumor necrosis factor D: increased amount of antigen-antibody complexes

Answer 77

D

Question 78

case 33: your patient is a 30 yo woman who was part of a tour group visiting a central american country. the day before leaving, several members of the group developed fever, abdominal cramps, and blood diarrhea a stool culture reveals no lactose-negative colonies on the EMB agar which one of the following is the most likely organisms to cause this infection? A: shigella dysenteriae B: salmonella enteritidis C: vibrio cholerae D: camphylobacter jejuni

Answer 78

D