MCQ – 89186

A patient admitted to an ICU is on a central venous line for the last one week. He is on ceftazidime and amikacin. After 7 days of antibiotics, he develops a spike of fever, and his blood culture is positive for gram-positive cocci in chains, which are catalase negative.Following this, vancomycin was started, but the culture remained positive for the same organism even after 2 weeks of therapy. The most likely organism causing infection is?

Correct Answer � C Explanation

Answer: Enterococcus faecalis Cor

1. From the case scenario, the most likely organism involved is Enterococcus faecalis.

2. The culture is catalase negative, so Staphylococcus aureus and coagulase-negative Staphylococcus are ruled out.

3. And Streptococcus viridans is usually sensitive to penicillin, except in neutropenic patients where vancomycin is given; hence, it is ruled out.

4. So, the points are in favor of Enterococcus faecalis.

5. Here, even after treatment with aminoglycoside, cephalosporin, and even with vancomycin, the culture remains positive. 

6.  So, this is a case of vancomycin-resistant enterococci. The mechanism is the alteration of the D- alanyl–D-alanine chain in cell wall.