Question 1

Which stage of syphilis is characterized by the appearance of a painless chancre, as shown in the image of a genital lesion?

Accepted Answer

Primary stage

Question 2

A patient presents with a bull’s eye rash after a tick bite and later develops joint pain. Which bacterium is most likely responsible, and what is the preferred treatment?

Accepted Answer

Borrelia burgdorferi; Doxycycline

Question 3

Which of the following is the main reservoir for Borrelia burgdorferi, the causative agent of Lyme disease?

Accepted Answer

Small field mice

Question 4

A urine culture from a patient with dysuria grows Gram-negative rods that ferment lactose and produce indole. Which organism is most likely responsible?

Accepted Answer

Escherichia coli

Question 5

Which enzyme produced by Proteus mirabilis is responsible for raising urine pH and contributing to kidney stone formation?

Accepted Answer

Urease

Question 6

A child develops bloody diarrhea after visiting a petting zoo. Laboratory tests reveal a Shiga-toxin producing E. coli. What is the most serious complication associated with this infection?

Accepted Answer

Hemolytic Uremic Syndrome (HUS)

Question 7

Which Gram-negative rod is associated with post-burn wound infections, produces a blue-green pigment, and is often resistant to antibiotics?

Accepted Answer

Pseudomonas aeruginosa

Question 8

A patient with peptic ulcers is found to have a Gram-negative, curved rod in the stomach mucosa. Which enzyme does this bacterium produce to survive the acidic environment?

Accepted Answer

Urease

Question 9

Which laboratory test is most appropriate for confirming the diagnosis of Neisseria gonorrhoeae in a male patient with urethral discharge?

Accepted Answer

Gram stain showing Gram-negative diplococci inside neutrophils

Question 10

A child presents with fever, stiff neck, and a petechial rash. Which organism is most likely responsible, and what is the primary mode of transmission?

Accepted Answer

Neisseria meningitidis; respiratory droplets

Question 11

Which of the following bacteria is transmitted by vehicles such as air or water and multiplies in alveolar macrophages, causing severe pneumonia in immunocompromised patients?

Accepted Answer

Legionella pneumophila

Question 12

A patient presents with massive, watery diarrhea described as 'rice-water stools.' Which bacterium is responsible, and what is the mainstay of treatment?

Accepted Answer

Vibrio cholerae; fluid and electrolyte replacement

Question 13

Which of the following is a distinguishing laboratory feature of Campylobacter jejuni?

Accepted Answer

Growth on CAMPY agar at $$42^\circC$$

Question 14

Which toxin is produced by Shigella dysenteriae and E. coli O157:H7, leading to hemolytic anemia and kidney damage?

Accepted Answer

Shiga-toxin

Question 15

A child under 4 years old develops meningitis and epiglottitis. Which encapsulated bacterium is most likely responsible?

Accepted Answer

Haemophilus influenzae type b

Question 16

Which of the following best describes the transmission route of Salmonella typhi?

Accepted Answer

Contact with human feces or carriers

Question 17

A patient with a history of burns develops a wound infection with a Gram-negative rod that forms biofilms and is resistant to multiple antibiotics. Which infection control measure is most important in the hospital setting?

Accepted Answer

Strict hand hygiene and equipment sterilization

Question 18

Which laboratory method is used to confirm the presence of antibodies against Borrelia burgdorferi in Lyme disease after an initial positive screening test?

Accepted Answer

Western blot

Question 19

Which of the following is a common sign of secondary syphilis, as seen in the provided images?

Accepted Answer

Generalized rash on palms and soles

Question 20

A patient with a history of exposure to turtles develops diarrhea. Which bacterium is most likely responsible, and what is the best diagnostic test?

Accepted Answer

Salmonella; stool culture

Microbiology Study Guide: Spirochetes and Gram-Negative Bacteria

Study Guide - Practice Questions

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