1. You are paged by the Microbiology Lab and told that blood
cultures drawn from your patient, Mrs. I. M. Septic, are growing
gram-positive cocci. Mrs. Septic is a 42-year-old woman who was
admitted with a fever and malaise. Which of the following is NOT
a possible cause of your patient's infection?
A. Enterococcus faecium
B. Streptococcus pyogenes
C. Staphylococcus aureus
D. Staphylococcus epidermidis
E. Listeria monocytogenes

2. E. Listeria is a Gram-positive rod, not coccus.

3. Anxious to narrow the differential diagnosis on Mrs. Septic,
you ask the Microbiology Lab for more information. They state
that they have not yet identified the organism, but they have
shown that it is catalase positive. Which two of the following
organisms are possible?
A. Enterococcus faecium
B. Streptococcus pyogenes
C. Staphylococcus aureus
D. Staphylococcus epidermidis
E. Listeria monocytogenes

4. C. and D. Streptococci and enterococci are catalase negative, whereas Listeria is a rod, not a cocci.
Staphylococci are catalase positive.

5. The next morning you again call the microbiology laboratory.
They now tell you that Mrs. Septic's bacterium is also coagulase
positive. Which organism is the cause of Mrs. Septic's infection?
A. Enterococcus faecium
B. Streptococcus pyogenes
C. Staphylococcus aureus
D. Staphylococcus epidermidis
E. Listeria monocytogenes

6. C. Staphylococcus aureus is coagulase positive whereas
Staphylococcus epidermidis is coagulase negative.

7. When you return to tell Mrs. Septic that you have identified the
organism that is making her ill, you notice that she is febrile,
hypotensive, is vomiting and has diarrhea and an erythematous
rash. She states that she is currently menstruating. Which of the
following toxins is most likely causing Mrs. Septic's symptoms?
A. exfoliatin
B. TSST-1
C. alpha-toxin
D. coagulase
E. pyrogenic exotoxin A

8. B. Mrs. Septic has the signs and symptoms of
toxic shock syndrome. Thus TSST-1
is the most likely causative toxin. Note that although
bacteremia is not necessary in the pathogenesis of
toxic shock syndrome, bacteremia may still be present
in these patients.

9. Which of the following organisms is NOT a common cause
of food-poisoning?
A. Staphylococcus aureus
B. Yersinia enterocolitica
C. Pseudomonas aeruginosa
D. Salmonella enterica
E. Bacillus cereus

10. C. Pseudomonas aeruginosa is a frequent cause of
hospital-acquired infections, but usually does not cause food poisoning.

11. All of the following organisms are associated with cardiac
damage and abnormalities EXCEPT:
A. Clostridium difficile
B. Staphylococcus aureus
C. Corynebacterium diphtheriae
D. Borrelia burgdorferi
E. Streptococcus pyogenes

12. A. Clostridium difficile causes antibiotic-associated diarrhea
and colitis, but not cardiac damage. Staphyloccocus aureus
is a frequent cause of endocarditis, Corynebacteria diphtheriae
can cause cardiac damage through the action of diphtheria
toxin, Borrelia burgdorferi is associated with cardiac damage
and arrhythmias, and Streptococcus pyogenes is associated
with rheumatic fever.

13. Which of the following is a strict anaerobe?
A. Corynebacterium diphtheriae
B. Actinomyces israelii
C. Bordetella pertussis
D. Yersinia pestis
E. Nocardia asteroides

14. B. Actinomyces israelii

15. A 34-year-old man presents to the Emergency Room
complaining of fever, a stiff neck, and pain upon looking
at bright lights. You suspect meningitis. All of the following
are likely causes of his illness EXCEPT:
A. Streptococcus pneumoniae
B. Listeria monocytogenes
C. Neisseria gonorrhea
D. Neisseria meningitidis
E. Haemophilis influenzae

16. C. Neisseria gonorrhea usually causes a sexually
transmitted disease, whereas the other listed organisms
are frequent causes of meningitis.

17. Upon further questioning, you determine that he works on a
dairy farm and recently drank some unpasteurized milk. This
information supports which of the following as a cause of
his symptoms?
A. Streptococcus pneumoniae
B. Listeria monocytogenes
C. Neisseria gonorrhea
D. Neisseria meningitidis
E. Haemophilis influenzae

18. B. Listeria monocytogenes is a cause of meningitis that
may be obtained by drinking unpasteurized mild.

19. You perform a lumbar puncture. A gram-stain of the
cerebral spinal fluid shows gram-negative diplococci. Which
of the following is the most likely cause of the man's illness?
A. Streptococcus pneumoniae
B. Listeria monocytogenes
C. Neisseria gonorrhea
D. Neisseria meningitidis
E. Haemophilis influenzae

20. D. Neisseria meningitidis is a frequent cause of
meningitis that is a Gram-negative diplococci (cocci
that are often paired).

21. The man states that he had an anaphylactic response to
penicillin in the past. What should you use to treat him?
A. penicillin
B. ceftriaxone
C. trimethroprim/sulfamethoxazole
D. gentamicin
E. chloramphenicol

22. E. Chloramphenicol is the treatment of choice for patients
with Neisseria meningitidis meningitis who have a severe
allergy to penicillin.

23. Regarding this case, which of the following is true?
A. Household members should receive meningococcal vaccine.
B. Household members should receive ciprofloxacin.
C. Household members should receive penicillin.
D. A lumbar puncture should be performed on all household
members to determine who should receive treatment.
E. Throat cultures should be performed on all household
members to determine who should receive antibiotics.

24. B. Household members exposed to a patient with
Neisseria meningitidis meningitis should receive
ciprofloxacin prophylaxis, since they are at a significantly increased risk of acquiring the disease. Rifampin and ceftriaxone are also acceptable options.

25. A throat culture is mistakenly ordered on a patient on your
service who is hospitalized for a diabetic foot ulcer. Her throat
looks normal and she denies any oropharyngeal symptoms. You
are surprised when the Clinical Microbiology Laboratory calls you
to say that the culture is growing Neisseria meningitidis. Which
of the following would be appropriate:
A. Start treatment immediately with penicillin and place the
patient in respiratory isolation.
B. Immunize her with the meningococcus vaccine.
C. Immunize the patient's family members as well as the physicians
and nurses who have cared for her with the meningococcus vaccine.
D. Administer ciprofloxacin to the patient's family members as
well as the physicians and nurses who have cared for her.
E. Take no action.

26. E. Take no action. The patient’s throat is transiently
colonized with Neisseria meningitidis, but he is not
currently experiencing disease. Approximately 10% of the population will be colonized with this bacterium at any given time. Therefore no treatment
or other measures is necessary.

27. A recent study showed that adults in an African country were more likely to get anthrax lesions on their hands and arms whereas children were more likely to have the lesions on their face. Why might this be so?

28. Children are more likely to acquire anthrax by fly bites whereas adults are more likely to acquire anthrax through contact with carcasses of infected animals.

29. Which of the following is true regarding Neisseria
meningitidis?
A. This organism secretes siderophores to obtain iron from host tissues.
B. This organism has a capsule which is the target of a
vaccine.
C. This organism causes a sexually transmitted disease.
D. This organism is a Gram-negative rod.
E. A single commercially available vaccine is effective against all
isolates of this organism.

30. B. Neisseria spp. do not secrete siderophores. Neisseria
gonorrhoeae causes a sexually transmitted disease, not
Neisseria meningitidis. This organism is a Gram-negative
diplococcus, not rod. A vaccine against the polysaccharide
capsule is used, but is only effective against capsular types
A, C, and Y. A separate vaccine is effective against capsular type B.

31. Which of the following is NOT a spirochete?
A. Treponema pallidum
B. Borrelia burgdorferi
C. Borrelia recurrentis
D. Leptospira interrogans
E. Helicobacter pylori

32. E. Helicobacter pylori is a Gram-negative spiral-
shaped organism, but is not considered a spirochete.

33. The bacterium that causes Lyme Disease makes which bacterial
protein?
A. VacA
B. ActA
C. OspA
D. OmpA
E. dot

34. C. OspA is an surface protein of Borrelia burgdorferi
C. OspA is an surface protein of Borrelia burgdorferi. VacA is a Helicobacter pylori protein, ActA is a Listeria monocytogenes protein, and dot is a genetic locus in Legionella pneumophila.

35. Which of the following is NOT a Rickettsia species
important in human disease?
A. Rickettsia typhi
B. Rickettsia tsutsugamushi
C. Rickettsia prowazekii
D. Rickettsia burnetti
E. Rickettsia rickettsia

36. D. burnetti is a species of Coxiella not Rickettsia
D. burnetti is a species of Coxiella not Rickettsia. Rickettsia typhi causes murine typhus, R. tsutsugamushi causes scrub typhus, R. prowazekii causes epidemic typhus, and R. rickettsia causes Rocky Mountain Spotted Fever.

37. Which of the following media/agars is routinely used
to grow Legionella pneumophila?
A. Buffered charcoal-yeast extract agar
B. Sheep red blood cell agar
C. MacConkey’s agar
D. Bordet-Gengou media
E. Tellurite selective media

38. A. Buffered charcoal yeast extract agar is commonly used
to grow Legionella pneumophila. This agar is supplemented
with cysteine and antibiotics, which aid in the growth and
selection of Legionella.

39. Which of the following organisms causes an illness
characterized by a “catarrhal stage.”
A. Listeria monocytogenes
B. Bordetella pertussis
C. Legionella pneumophila
D. Bacillus anthracis
E. Coxiella burnetti

40. B. Bordetella pertussis causes whooping cough, a disease
consisting of three stages: (1) an incubation stage, (2) a
catarrhal stage, and (3) a paroxysmal stage, during which
the characteristic “whooping” cough occurs.

41. Your patient is admitted to the surgical intensive care unit
following a car accident leading to abdominal trauma.
He undergoes abdominal surgery for removal of his spleen,
which has ruptured. He remains intubated following the
surgery, and on post-op day 3 develops a fever and infiltrate
on his chest XRay. Sputum and blood cultures grow an
organism that is a rod by Gram-stain. Which of the
following is NOT a possible etiology for this patient’s pneumonia?
A. Klebsiella pneumoniae
B. Pseudomonas aeruginosa
C. Citrobacter freundii
D. Enterbacter cloacae
E. Legionella pneumophila

42. E. All have a Gram-negative structure to their
cell walls, but Legionella pneumophila does not take
up Gram-stain. It is visualized using other stains, such
as silver stain or DFA.

43. Preliminary analysis of the organism by the Microbiology
Laboratory indicates that it is oxidase positive. Which of
the following is/are possible causes of the patient’s
pneumonia?
A. Klebsiella pneumoniae
B. Pseudomonas aeruginosa
C. Citrobacter freundii
D. Enterbacter cloacae
E. Legionella pneumophila

44. B. Only Pseudomonas aeruginosa is a Gram-negative
rod that is oxidase positive.

45. The laboratory says that antibiotic susceptibilities on the P
The laboratory says that antibiotic susceptibilities on the P. aeruginosa isolate are pending. Which of the following is an appropriate treatment regimen for this patient?
A. Ceftriaxone + gentamicin
B. Ceftazidime + tobramycin
C. Imipenem
D. Ciprofloxacin
E. Piperacillin-tazobactam

46. B. Serious P. aeruginosa infections should be empirically treated with two antipseudomonal drugs until susceptibilities are known. P. aeruginosa tends to be resistant to many antibiotics. To increase the likelihood that the patient will receive at least one active antibiotic, two antipseudomonal antibiotics are given empirically. Note that ceftriaxone is not an antipseudomonal antibiotic—it does not have activity against P. aeruginosa.

47. Which of the following is not associated with the cell
wall of Gram-positive bacteria?
A. Lipopolysaccharide
B. Murein
C. Teichoic acid
D. Peptidoglycan
E. Penicillin-binding proteins

48. A. Lipopolysaccharide is associated with the outer
membrane of Gram-negative bacteria.

49. Which of the following is the toxic portion of
lipopolysaccharide?
A. O-side chain
B. Core polysaccharide
C. Lipid A
D. KDO
E. ribotol

50. C. Lipid A is responsible for the toxic activity of LPS,
which can lead to Gram-negative shock.

51. “H antigen” refers to which of the following:
A. Pili
B. Capsule
C. Flagella
D. LPS
E. Peptidoglycan

52. C. Flagellum serotype

53. Which of the following genes are routinely sequenced
to determine phylogenetic relationships between
bacteria?
A. 18s rRNA
B. 50s ribosomal subunit
C. 23s rRNA
D. 16s rRNA
E. 5s rRNA

54. D. The 16s rRNA gene is often sequenced and compared
to known sequences to determine evolutionary
relationships between bacteria.

55. Which of the following does NOT involve the
proton-motive force?
A. Respiration
B. Electron transport chain
C. Chemiosmosis
D. ATP synthase
E. Fermentation

56. E. Fermentation. Energy generation by fermentation
does not require an electron transport chain and does
not involve the generation of a proton-motive force.

57. Which of the following is generally NOT true of
facultative bacteria?
A. They contain superoxide dismutase.
B. They contain catalase.
C. They often ferment in the absence of oxygen.
D. They often respire in the presence of oxygen
E. They are unable to grow in the absence
of oxygen.

58. E. Facultative bacteria by definition can grow in the
presence and absence of oxygen.

59. A sex pilus is involved in which of the following?
A. Transformation
B. Conjugation
C. Transduction
D. Electroporation
E. Adherence to eukaryotic cells

60. B. Conjugation

61. Which of the following statements about phages is
true?
A. Virulent phages may cause a lysogenic infection.
B. Temperate phages may cause a lytic infection.
C. Bacteriophages are viruses that infect eukaryotic cells.
D. Genetic exchange mediated by phages is referred to
as transformation.
E. There are two types of transduction: natural and
artificial.

62. B. Temperate phages may cause either a lytic or a
lysogenic infection. Virulent phages may cause only
a lytic infection.

63. Treatment of Clostridium difficile infections may include the
use of fecal transplants to prevent recurrence.
A. True
B. False

64. A. True. Fecal transplants restore the gastrointestinal microflora, which tends to prevent relapse of C. difficile disease.

65. Which of the following organisms does NOT use a type III
secretion system to cause disease?
A. Yersinia pestis
B. Pseudomonas aeruginosa
C. Staphylococcus aureus
D. Salmonella enterica
E. Shigella flexneri

66. C. Staphylococcus aureus is a Gram-positive organism.
Gram-positive bacteria do not harbor type III secretion
systems. Type III secretion systems are embedded in both the inner and outer bacterial membranes. Gram-positive bacteria don’t have an outer membrane.

67. You see in clinic a 23 year-old-woman who recently immigrated from Vietnam. She states that she was referred to you because the PPD skin test she received during her immigration screening was positive. She has never received the BCG vaccine. She denies coughing, fever, night sweats, and weight loss. After taking a complete history and doing a physical exam, which of the following would be most appropriate?
A. Start isoniazid.
B. Start isoniazid and order a chest X-ray.
C. Start isoniazid, rifampin, ethambutol, and pyrazinamide.
D. Order three sputums to be collected and examined for acid-fast bacilli
E. Order a chest X-ray.

68. E. Order a chest X-ray. You must first determine whether the patient has latent tuberculosis or active disease. You would do this by obtaining a chest X-ray even if the patient were not complaining of symptoms. A chest X-ray is the accepted method of excluding active pulmonary tuberculosis in someone who is asymptomatic. It is important to discriminate between latent tuberculosis and active disease because the former could be treated with a single drug, but active disease should be initially treated with four drugs. Treatment of active disease, even transiently, with a single drug has the potential to lead to resistance.

69. Which of the following bacteria exhibit coiling phagocytosis?
A. Legionella pneumophila
B. Coxiella burnetti
C. Francisella tularensis
D. Bartonella quintana
E. Salmonella enterica

70. A. Legionella pneumophila

71. Which of the following bacteria is a cause of cancer?
A. Pseudomonas aeruginosa
B. Streptococcus pyogenes
C. Bartonella quintana
D. Francisella tularensis
E. Helicobacter pylori

72. E. Helicobacter pylori has been linked toadenocarcinoma, non-Hodgkin's lymphoma, and low-grade B cell mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach

73. Which of the following is NOT true of Leptospira interrogans?
A. It can be transmitted by ingestion of contaminated water
B. It can be transmitted by exposure of cuts in the skin to contaminated water.
C. It can be transmitted by exposure of the conjunctiva to contaminated water
It can be transmitted by inhalation of bacteria aerosolized during the birth of animals
It also commonly infects rats, cattle, and dogs

74. D. Leptospira cannot be transmitted by inhalation of bacteria aerosolized during the birth of animals. This route of infection is typical of Coxiella burnetti.