Disk diffusion, agar dilution and the E-test for susceptibility testing of Corynebacterium jeikeium

Abstract

OBJECTIVE: The susceptibilities to penicillin, tetracycline, erythromycin, gentamicin, vancomycin and teicoplanin of 58 strains of Corynebacterium jeikeium were assessed by disk diffusion and agar dilution reference methods. METHODS: Zone sizes and minimal inhibitory concentrations (MIC) by agar dilution were interpreted using the ranges in the NCCLS tables for organisms other than Haemophilus, Neisseria gonorrhoeae, and Streptococcus pneumoniae. RESULTS: By agar dilution, 14%, 88%, 17% and 26% of the 58 isolates were susceptible to penicillin, tetracycline, erythromycin, and gentamicin, respectively. Using the breakpoints for Listeria monocytogenes, all strains showed concordant results for penicillin by disk diffusion. Discrepancies in the interpretative categories by disk diffusion were found in four cases (two very major and two minor) for tetracycline, in nine (two very major, two major, and five minor) for erythromycin, and in 1 case (very major) for gentamicin. All 58 strains were susceptible to vancomycin and teicoplanin by agar dilution and disk diffusion. The overall agreement of interpretative disk diffusion for all six antibiotics was 95.9%. In addition, all strains were susceptible to both glycopeptides by E-test. However, for vancomycin the MIC results in 58.6% were two log2 dilutions and in 1.7% more than two log2 dilutions higher by E-test than by agar dilution, whereas for teicoplanin agreement within one log2 dilution was 100%. CONCLUSIONS: Further evaluation of methodologies of disk diffusion is required to obtain a better agreement for erythromycin and tetracycline. The criteria of the NCCLS for interpretation of disk diffusion are adequate for susceptibility testing of C. jeikeium to penicillin, gentamicin, vancomycin and teicoplanin.

Antibiotic Susceptibility Testing (Agar Disk Diffusion and Agar Dilution) of Clinical Isolates of <i>Corynebacterium jeikeium</i>

“…Previous investigators noted that C. jeikeium isolates uniformly were susceptible to the glycopeptide antibiotics teicoplanin and vancomycin [6][7][8]49] and the experimental drug daptomycin [50]; our data were corroboratory. It should be stressed though that vancomycin was effective for chemotherapy of infection, but not for eradication of skin colonization [24].…”

“…With few exceptions, and like Pennekamp et al [49], we encountered very few discrepancies. The latter group of investigators proposed to adopt NCCLS interpretive criteria of penicillin G for Listeria monocytogenes as surrogate markers for C. jeikeium, i.e., a breakpoint of ^2 Ìg/ml; our data appear to indicate that the enterococcal breakpoint of ^8 Ìg/ml of penicillin G would perform just as well (table 2).…”

“…Our data confirm those of Dealler [50] with respect to the variable susceptibility of C. jeikeium to fusidic acid and rifampin and the uniform resistance of this microorganism to mupirocin. Furthermore, the less variable resistance of C. jeikeium to penicillin G and erythromycin had been noted by Pennekamp et al [49], among others. Interestingly, doxycycline was somewhat more active than tetracycline (tables 1, 2).…”

Calibration of the disk diffusion test for trovafloxacin susceptibility testing of four anaerobic species

“…The E test values were always lower, down to 50% of the reference MIC values. Such discrepancies have been described by several authors for other antibiotics and aerobic as well as anaerobic isolates [26–28], both towards higher values [29–31] and lower values [32,33]. Basically, the E test is a diffusion method and it was originally described and patented by Professor Olof Vesterberg (Swedish Patent no.…”

MIC determination of fusidic acid and of ciprofloxacin using multidisk diffusion tests

“…The fact that the inhibition zone measurements can be processed in the local computer also offers other advantages. It has been reported that E test results sometimes deviate from the true MIC values [22–24], with values higher than the MIC [25–28] as well as lower than the MIC [29–32], sometimes depending on the combination of drug and species [33]. It has even been observed that E test deviations from the true MIC are greater at higher MIC values [28].…”