[A case with Abiotrophia defectiva isolated from postoperative blood culture of a patient with diffuse peritonitis]

We have recently detected Abiotrophia defectiva (A. defectiva) from postoperative blood culture of a patient with diffuse peritonitis. Pleomorphic Gram positive rod appearance and no growth on a standard sheep blood agar led us to suspect aerotolerant anaerobe. From the test results of simplified identification kit for anaerobes, we tentatively reported Clostridium tertium (C. tertium) to the clinician. However, the analysis of 16SrRNA sequence proved it to be A. defectiva. When Gram positive coccus or pleomorphic Gram positive rod are observed on blood culture, it is recommended to incubate Brucella HK (RS) blood agar plates for 24 hours at 35 degrees C both aerobically and anaerobically. The growth both aerobically and anaerobically suggests A. defectiva and Satellitism test and Rapid ID 32 STREP(SYSMEX) testing should be performed to identify the responsible bacteria. A. defectiva is Gram positive streptococcus and requires pyridoxal hydrochloride or L-cysteine to grow. It could be unidentified or misidentified and its particularity often leads incomplete report to the clinician. Our study shows that more careful examination will increase the detection of A. defectiva.