Which organism is described as multidrug resistant, nonmotile, nonhemolytic gram-positive bacilli that are resistant to penicillin but sensitive to vancomycin?

Which organism is described as multidrug resistant, nonmotile, nonhemolytic gram-positive bacilli that are resistant to penicillin but sensitive to vancomycin?

• A. Erysipelothrix rhusiopathiae
• B. Corynebacterium jeikium
• C. Listeria monocytogenes
• D. Corynebacterium diphtheriae

Answer: (B)

The pattern being tested is how antibiotic resistance together with basic phenotypic traits points to a specific gram-positive bacillus. When a nonmotile, nonhemolytic gram-positive rod is resistant to penicillin but remains susceptible to vancomycin, the organism that fits best is Corynebacterium jeikeium. This species is notorious in hospital settings as a multidrug-resistant pathogen, often causing bloodstream infections or device-related infections in patients with weakened defenses or implanted devices. Its typical treatment relies on vancomycin because many beta-lactam antibiotics, including penicillin, are ineffective against it. Other gram-positive rods listed may have different motility or hemolysis patterns and are not characteristically defined by this exact penicillin-resistant/vancomycin-susceptible profile, so they don’t fit as well.

The pattern being tested is how antibiotic resistance together with basic phenotypic traits points to a specific gram-positive bacillus. When a nonmotile, nonhemolytic gram-positive rod is resistant to penicillin but remains susceptible to vancomycin, the organism that fits best is Corynebacterium jeikeium. This species is notorious in hospital settings as a multidrug-resistant pathogen, often causing bloodstream infections or device-related infections in patients with weakened defenses or implanted devices. Its typical treatment relies on vancomycin because many beta-lactam antibiotics, including penicillin, are ineffective against it. Other gram-positive rods listed may have different motility or hemolysis patterns and are not characteristically defined by this exact penicillin-resistant/vancomycin-susceptible profile, so they don’t fit as well.