A woman in her 80s with a history of an atrial valve replacement has had a recurring fever since the summer time. After several rounds of outpatient antibiotics and even a previous hospital admission, she was admitted again after 5 months of this fever of unknown origin. She had extreme weakness, low platelets, elevated troponin and a heart murmur. Previous blood cultures were negative. It appeared like endocarditis, but cardiology was (initially) hesitant to perform the more invasive (but informative) transesophogeal echocardiogram (TEE), since the original imaging was inconclusive, and new blood cultures were still negative. The TEE was eventually performed, and while it confirmed valve calcification, there weren't obvious vegetations that would suggest acute endocarditis. 

Eventually, 4.5 days after being collected in the ED, blood cultures became positive with small gram-negative coccobacilli. On solid media, the organism grew only on chocolate agar (after 48hrs)—no growth on SBA or MAC.

What organism(s) might you suspect and what biochemical tests should be performed?

Watch the reveal now!

Author Information

Richard E. Davis, PhD, D(ABMM), MLS(ASCP), Microbiology Director, Providence Sacred Heart Medical Center and Children’s Hospital.
Stay up to date on all ASM Clinical Public Health Microbiology (CPHM) activities when you sign up for our monthly CPHM Newsletter. Be the first to know about free educational webinars, continuing education credit opportunities, advocacy, updated guidelines and more.