Prevalence of Corynebacteria in diabetic foot infections

Microbiological flora of diabetic foot infections are usually polymicrobial and frequently include bacteria of the Corynebacterium sp. (diphtheroids). The purpose of this study was to determine the prevalence of these bacteria in both deep and superficial cultures in diabetic patients with foot infections.

The charts of 50 patients of successive admissions to the Orthopedic-Diabetes Service at our hospital were reviewed to obtain the following data: age, sex, ethnic origin, method of treatment of diabetes, blood glucose level, prior antibiotics, and reports of cultures taken from bedside and intraoperative sites. Data were analyzed to compare the prevalence of diphtheroids in reliable versus nonreliable cultures and the influence of other parameters on the presence of these organisms.

Fourteen of 19 (74%) of the intraoperative specimens grew diphtheroids compared with 25 of 65 (39%) of the bedside cultures, a highly significant difference. In addition, there was a somewhat greater occurrence of diphtheroids in women compared with men. The likelihood that contamination is the cause for the presence of diphtheroids is highly unlikely, because one arm of the study included cultures derived from deep tissue at the time of the surgical procedure (i.e., the intraoperative cultures). Cultures always grew at least one other organism in addition to the diphtheroid.

Corynebacteria, commonly known as diphtheroids, are present as a part of the polymicrobial flora in a large percentage of diabetic patients with foot infections. Because the diphtheroids were identified in culture material taken in the operating room or at the time of incision and drainage in a higher percentage of patients than in specimens from superficial cultures, it is highly unlikely that they are contaminants.