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?
Staphylococcus aureus Incorrect
Enterococcus faecalis Correct
Answer: Enterococcus faecalis Cor
From the case scenario, the most likely organism involved is Enterococcus faecalis.
The culture is catalase negative, so Staphylococcus aureus and coagulase-negative Staphylococcus are ruled out.
And Streptococcus viridans is usually sensitive to penicillin, except in neutropenic patients where vancomycin is given; hence, it is ruled out.
So, the points are in favor of Enterococcus faecalis.
Here, even after treatment with aminoglycoside, cephalosporin, and even with vancomycin, the culture remains positive.
- So, this is a case of vancomycin-resistant enterococci. The mechanism is the alteration of the D- alanyl–D-alanine chain in cell wall.