MCB 1000L Case Study 4: Rat Bite Fever |
Questions and Answers | Microbiology
Laboratory | 2026/2027 Updated | 100%
Correct
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This exam covers the clinical microbiology, epidemiology, pathogenesis, laboratory diagnosis, and treatment
of rat bite fever, with emphasis on Streptobacillus moniliformis and Spirillum minus. It integrates case-based
reasoning with laboratory identification, antimicrobial selection, and zoonotic risk assessment.
STUDY GUIDE
Recommended duration: 3 hours. Passing target: 70%.
HIGHP - Page 1 of 17
,1. A patient presents with fever, rash, and polyarthritis after a rat bite. Which culture
medium is most appropriate for isolating the causative agent of rat bite fever?
[ ] A. MacConkey agar
[ ] B. Blood agar with 5% sheep blood
[ ] C. Thayer-Martin agar
[ ] D. Sodium polyanethol sulfonate (SPS) broth
CORRECT: D. Sodium polyanethol sulfonate (SPS) broth
Streptobacillus moniliformis requires enriched media with SPS to inhibit gram-positive organisms and is often
cultured in SPS broth. MacConkey inhibits gram-positive bacteria, Thayer-Martin is for Neisseria, and blood
agar alone may not suppress contaminants.
2. Which of the following best describes the Gram stain morphology of Streptobacillus
moniliformis?
[ ] A. Gram-negative fusiform bacilli with bulbous ends
[ ] B. Gram-positive spore-forming bacilli
[ ] C. Gram-negative spirochetes
[ ] D. Gram-positive cocci in clusters
CORRECT: A. Gram-negative fusiform bacilli with bulbous ends
S. moniliformis is a Gram-negative pleomorphic bacillus with characteristic bulbous or fusiform ends.
Spirochetes describe Spirillum minus, while the other options are unrelated.
3. A patient with rat bite fever develops endocarditis. Which complication is most
characteristic of Streptobacillus moniliformis infection?
[ ] A. Acute glomerulonephritis
[ ] B. Septic arthritis
[ ] C. Hepatosplenomegaly
[ ] D. Endocarditis
CORRECT: D. Endocarditis
Endocarditis is a well-known complication of S. moniliformis infection, occurring in up to 10% of cases. Septic
arthritis and hepatosplenomegaly can occur but are less specific. Glomerulonephritis is not typical.
4. Which of the following laboratory findings is most consistent with rat bite fever caused
by Spirillum minus?
[ ] A. Positive culture on SPS broth
[ ] B. Visualization of spirochetes on darkfield microscopy
[ ] C. Growth on MacConkey agar
HIGHP - Page 2 of 17
, [ ] D. Positive oxidase test
CORRECT: B. Visualization of spirochetes on darkfield microscopy
S. minus is a spirochete that can be visualized by darkfield microscopy or Giemsa stain but does not grow on
standard culture media. SPS broth is for S. moniliformis, and the other tests are not relevant.
5. A patient with rat bite fever is allergic to penicillin. Which antimicrobial is the most
appropriate alternative for treating Streptobacillus moniliformis?
[ ] A. Doxycycline
[ ] B. Vancomycin
[ ] C. Gentamicin
[ ] D. Metronidazole
CORRECT: A. Doxycycline
Doxycycline is an effective alternative for penicillin-allergic patients with rat bite fever. Vancomycin,
gentamicin, and metronidazole are not first-line and may be less effective.
6. Which of the following statements about the epidemiology of rat bite fever is correct?
[ ] A. It is most commonly transmitted by flea bites.
[ ] B. It is caused by a virus.
[ ] C. It is a zoonotic infection transmitted by rodents.
[ ] D. It is exclusively found in developing countries.
CORRECT: C. It is a zoonotic infection transmitted by rodents.
Rat bite fever is a zoonotic bacterial infection transmitted primarily by rats and other rodents. It is not viral, not
flea-borne, and occurs worldwide.
7. A laboratory technologist is processing a blood culture from a patient with suspected
rat bite fever. Which of the following best describes the growth characteristics of
Streptobacillus moniliformis?
[ ] A. Rapid growth within 24 hours on sheep blood agar
[ ] B. Requires CO2 and grows as satellite colonies around Staphylococcus aureus
[ ] C. Grows as L-phase variants requiring cholesterol
[ ] D. Forms endospores under aerobic conditions
CORRECT: B. Requires CO2 and grows as satellite colonies around Staphylococcus aureus
S. moniliformis often requires enriched CO2 conditions and may exhibit satellite growth near S. aureus. It
does not form spores or grow rapidly on standard blood agar without enrichment.
HIGHP - Page 3 of 17
Questions and Answers | Microbiology
Laboratory | 2026/2027 Updated | 100%
Correct
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
50 exam-style multiple-choice questions. Each question includes the correct answer and a complete rationale
for focused revision.
COVERAGE
This exam covers the clinical microbiology, epidemiology, pathogenesis, laboratory diagnosis, and treatment
of rat bite fever, with emphasis on Streptobacillus moniliformis and Spirillum minus. It integrates case-based
reasoning with laboratory identification, antimicrobial selection, and zoonotic risk assessment.
STUDY GUIDE
Recommended duration: 3 hours. Passing target: 70%.
HIGHP - Page 1 of 17
,1. A patient presents with fever, rash, and polyarthritis after a rat bite. Which culture
medium is most appropriate for isolating the causative agent of rat bite fever?
[ ] A. MacConkey agar
[ ] B. Blood agar with 5% sheep blood
[ ] C. Thayer-Martin agar
[ ] D. Sodium polyanethol sulfonate (SPS) broth
CORRECT: D. Sodium polyanethol sulfonate (SPS) broth
Streptobacillus moniliformis requires enriched media with SPS to inhibit gram-positive organisms and is often
cultured in SPS broth. MacConkey inhibits gram-positive bacteria, Thayer-Martin is for Neisseria, and blood
agar alone may not suppress contaminants.
2. Which of the following best describes the Gram stain morphology of Streptobacillus
moniliformis?
[ ] A. Gram-negative fusiform bacilli with bulbous ends
[ ] B. Gram-positive spore-forming bacilli
[ ] C. Gram-negative spirochetes
[ ] D. Gram-positive cocci in clusters
CORRECT: A. Gram-negative fusiform bacilli with bulbous ends
S. moniliformis is a Gram-negative pleomorphic bacillus with characteristic bulbous or fusiform ends.
Spirochetes describe Spirillum minus, while the other options are unrelated.
3. A patient with rat bite fever develops endocarditis. Which complication is most
characteristic of Streptobacillus moniliformis infection?
[ ] A. Acute glomerulonephritis
[ ] B. Septic arthritis
[ ] C. Hepatosplenomegaly
[ ] D. Endocarditis
CORRECT: D. Endocarditis
Endocarditis is a well-known complication of S. moniliformis infection, occurring in up to 10% of cases. Septic
arthritis and hepatosplenomegaly can occur but are less specific. Glomerulonephritis is not typical.
4. Which of the following laboratory findings is most consistent with rat bite fever caused
by Spirillum minus?
[ ] A. Positive culture on SPS broth
[ ] B. Visualization of spirochetes on darkfield microscopy
[ ] C. Growth on MacConkey agar
HIGHP - Page 2 of 17
, [ ] D. Positive oxidase test
CORRECT: B. Visualization of spirochetes on darkfield microscopy
S. minus is a spirochete that can be visualized by darkfield microscopy or Giemsa stain but does not grow on
standard culture media. SPS broth is for S. moniliformis, and the other tests are not relevant.
5. A patient with rat bite fever is allergic to penicillin. Which antimicrobial is the most
appropriate alternative for treating Streptobacillus moniliformis?
[ ] A. Doxycycline
[ ] B. Vancomycin
[ ] C. Gentamicin
[ ] D. Metronidazole
CORRECT: A. Doxycycline
Doxycycline is an effective alternative for penicillin-allergic patients with rat bite fever. Vancomycin,
gentamicin, and metronidazole are not first-line and may be less effective.
6. Which of the following statements about the epidemiology of rat bite fever is correct?
[ ] A. It is most commonly transmitted by flea bites.
[ ] B. It is caused by a virus.
[ ] C. It is a zoonotic infection transmitted by rodents.
[ ] D. It is exclusively found in developing countries.
CORRECT: C. It is a zoonotic infection transmitted by rodents.
Rat bite fever is a zoonotic bacterial infection transmitted primarily by rats and other rodents. It is not viral, not
flea-borne, and occurs worldwide.
7. A laboratory technologist is processing a blood culture from a patient with suspected
rat bite fever. Which of the following best describes the growth characteristics of
Streptobacillus moniliformis?
[ ] A. Rapid growth within 24 hours on sheep blood agar
[ ] B. Requires CO2 and grows as satellite colonies around Staphylococcus aureus
[ ] C. Grows as L-phase variants requiring cholesterol
[ ] D. Forms endospores under aerobic conditions
CORRECT: B. Requires CO2 and grows as satellite colonies around Staphylococcus aureus
S. moniliformis often requires enriched CO2 conditions and may exhibit satellite growth near S. aureus. It
does not form spores or grow rapidly on standard blood agar without enrichment.
HIGHP - Page 3 of 17
