Systemic Bacteriology · NEET PG Preparation Microbiology
A 68-year-old man with acute myeloid leukemia undergoing chemotherapy presents with high-grade fever and chills. Blood cultures grow gram-positive ba…
Practice question from Systemic Bacteriology (NEET PG Preparation Microbiology), with the correct answer and a step-by-step solution.
hard · MCQ · Q-E264DC
A 68-year-old man with acute myeloid leukemia undergoing chemotherapy presents with high-grade fever and chills. Blood cultures grow gram-positive bacilli that form colonies with narrow zones of beta-hemolysis on blood agar. The organism exhibits tumbling motility at room temperature (25°C) and forms an umbrella-like pattern of motility in semisolid agar at room temperature. What is the most likely etiologic agent?
- A.Erysipelothrix rhusiopathiae
- B.Listeria monocytogenesCorrect answer
- C.Corynebacterium jeikeium
- D.Bacillus cereus
Solution
Listeria monocytogenes is a facultative intracellular, gram-positive bacillus that causes severe infections (meningitis, bacteremia) in immunocompromised patients and pregnant women. It is characterized by tumbling motility at 20-25°C and an umbrella-like growth pattern in semisolid motility media just below the surface at room temperature. It is also beta-hemolytic, mimicking Streptococcus agalactiae (Group B Strep), but is distinguished by being catalase-positive and motile.
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