Actualités de l′épidémiologie et du rôle pathogène des corynébactéries

Abstract

The corynebacteria are aerobically growing, asporogenous, irregularly shaped gram-positive rods. During the last few years, there has been an increase in the number of publications claiming an association of coryneform bacteria with disease. The well-known species Corynebacterium diphtheriae, agent of diphteria, is still endemic in many countries of all continents but it can be also isolated in France from serious infections such as endocarditis. The related species C. ulcerans can produce a diphtheria-like toxin and was isolated from wounds in humans after cat or dog bites. Many lipophilic species such as C. jeikeium and C. urealyticum are recognized as pathogens responsible for septicaemia and urinary tract infections, respectively, but several reports have recently associated granulomatous mastitis in women to the presence of other lipophilic bacteria notably the recently described species C. kroppenstedtii. Other Corynebacterium species are associated with infections such as C. aurimucosum ( C. nigricans) isolated from female genital infections and C. glucuronolyticum isolated from male genital infections. Some species of the closely related anaerobic genera Actinomyces such as A. neuii can grow in aerobic atmosphere and cause subcutaneous abscesses not histologically related to actinomycosis. Recently, the Actinomyces related genus Actinobaculum has been documented to cause urinary tract infection. Susceptibility testing should always be performed with clinically relevant isolates by using a disk diffusion method but also by determining the MIC and the MBC in the case of penicillin tolerant C. diphtheriae isolates. Recently, the CLSI/NCCLS has published guidelines for the susceptibility testing of Corynebacterium isolates as well as for the interpretive criteria. The species C. jeikeium and C. urealyticum are mainly resistant to antibiotics except to glycopeptides, but other species can show resistance to one class of antibiotics. Mechanism of resistance to β-lactams is probably based on modified cell wall components such as porins. For other antibiotics such as macrolides, modification of targets can explain resistance. Microbiologists should be now aware of the potential pathogenic role of these corynebacteria in order to accurately isolate and identify them from some clinical specimens.