COMPARISON OF ANTIMICROBIAL SUSCEPTIBILITIES OF CORYNEBACTERIUM SPECIES BY BROTH MICRODILUTION AND DISK DIFFUSION METHODS

Corynebacterium species are increasingly being implicated in foreign-b ody infections and in immunocompromised-host infections. However, ther e are no specific recommendations on the method or the criteria to use in order to determine the in vitro activities of the antibiotics comm only used to treat Corynebacterium infections, The first aim of our st udy was to compare the susceptibilities of various species of Coryneba cterium to vancomycin, erythromycin, and penicillin by using a broth m icrodilution method and a disk diffusion method, Second, the activity of penicillin against our isolates was assessed by using the interpret ative criteria recommended by the National Committee for Clinical Labo ratory Standards for the determination of the susceptibility of strept ococci and Listeria monocytogenes to penicillin, Overall, 100% of the isolates were susceptible to vancomycin, while considerable variations in the activities of erythromycin and penicillin were noted for the d ifferent species tested, including the non-Corynebacterium jeikeium sp ecies. A good correlation in the susceptibilities of vancomycin and er ythromycin between the disk diffusion and the microdilution methods wa s observed, However, a 5% rate of major or very major errors was detec ted with the Listeria criteria, while a high rate of minor errors (18% ) was noted when the streptococcus criteria were used, Our findings in dicate considerable variations in the activities of erythromycin and p enicillin against the various species of Corynebacterium, Because of t he absence of definite recommendations, important discrepancies were o bserved between the methods and the interpretations of the penicillin activity.