Microbiology – MCQ 6 – A patient in an ICU is on central venous line for the past one week.

A patient in an ICU is on central venous line for the past one week. He is on ceftazidime and 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 10 days of therapy. The most likely organism causing this infection is
A. Staphylococcus aureus A
B. Virdans streptococci
C. Enterococcus faecalis
D. Coagulase negative staphylococcus

Correct answer : C. Enterococcus faecalis

Catalase negative gram positive cocci in chains – indicates that they are staphylococci. Enterococci are commonly seen in hospital acquired infections and they are resistant to cephalosporins and even to vancomycin.