Isolation of coryneform bacteria from blood cultures of patients at a University Hospital in Saudi Arabia

ABSTRACT

Coryneform bacteria have been increasingly recognized as opportunistic pathogens in recent years. The aim of this study is to identify and determine the antimicrobial susceptibility of coryneform bacteria isolated from blood cultures of patients seen at King Khalid University Hospital [KKUH], Riyadh, Kingdom of Saudi Arabia and review the literature. All coryneform bacteria isolated from blood culture specimens between January 2001 and March 2003 were prospectively identified by API Coryne System [BioMerieux, France]. Clinical data were collected from each patient's medical record. Antimicrobial susceptibility to 16 antimicrobial agents were determined by minimum inhibitory concentration [MIC] using E-test [AB Biodisk, Solna, Sweden]. Out of 50 coryneform bacteria isolated, 19 different species were identified. Corynebacterium propinquum was the most common species 6/50 [12%] followed by Corynebacterium auris 5/50 [10%], Corynebacterium afermentans, Corynebacterium striatum, Dermabacter hominis, Brevibacterium, and Arthrobacter species 4/50 [8%] each. Underlying chest diseases were common among the patients 11/50 [22%], followed by different surgeries 10/50 [20%]. Of all, 12/50 [24%] patients were from different intensive care units [ICUs], 36/50 [72%] had either vascular, urinary or respiratory intubation. Three patients in ICUs died, one was an elderly patient with gastrointestinal bleeding and 2 teenagers [one had tracheoesophageal fistula and the other was post-arrest road traffic accident patient]. Vancomycin was the most active antimicrobial agent against all coryneform species. The majority had MIC <1 ug/ml. For most isolates, the MIC90s of erythromycin, clindamycin, and ciprofloxacin were above the break points. Corynebacterium striatum was the only isolate susceptible to ampicillin. This study revealed that coryneform bacteria are increasingly being recognized as a cause of serious infections in immunocompromised patients. We recommend identification and susceptibility testing of predominant isolates of coryneform bacteria from different clinical sites of seriously ill patients to select the antimicrobial agent necessary for clinical intervention