Detection of the ermX determinant of macrolide resistance in clinical strains of Corynebacterium urealyticum

Abstract number: 1134_02_425

Ortiz A., García-Cía J.I., Fernández-Roblas R., Esteban J.

Objectives:

To detect the presence of the ermX macrolide resistance gene in clinical isolates of C. urealyticum.

Methods:

57 C. urealyticum strains were isolated from clinical samples in the Fundación Jiménez Díaz hospital. The strains were maintained frozen until the studies to evaluate macrolide resistance were performed. Antibiotic susceptibility testing was performed by agar dilution assay in 14 cases and by disc diffusion assay in 43 cases. Detection of ermX gene was performed by using primers Cerm-1 and Cerm-2 according to the protocol described by Rosato et al. DNA was extracted by boiling a suspension of bacteria in distilled water. Amplification products were analysed by agarose gel electrophoresis and molecular weight of the amplicons were calculated by using the PhotoCapt software (BioGene, USA).

Results:

46 strains were resistant to erythromycin and clindamycin, and 11 were susceptible to both antimicrobials. We detected the gen ermX in 34 cases (all of them resistant). 12 macrolide-resistant strains gave negative results for ermX detection. The susceptible strains did not show any amplification product.

Conclusions:

The ermX gene is detected in 73.9 % of macrolide-resistant Corynebacterium urealyticum strains. However, there were 26.1 % macrolide-resistant strains in which ermX gene was not detected. Other resistance determinants must be involved in macrolide resistance among Corynebacterium urealyticum.