Macrolide, Lincosamide, and Streptogramin B–Constitutive-Type Resistance inCorynebacterium pseudodiphtheriticumIsolated from Upper Respiratory Tract Specimens

Abstract

Corynebacterium pseudodiphtheriticum is commonly found in normal upper respiratory tract flora in humans. In certain conditions it can cause the opportunistic infections, especially in immunocompromised patients. In certain strains of Corynebacterium sp., the macrolide, lincosamide, and streptogramin B (MLSb) resistance mechanism related to the presence of the erm(X) gene was discovered; hence, the need appeared for further investigation to confirm the existence of this gene among C. pseudodiphtheriticum. About 58 strains of C. pseudodiphtheriticum were used in this study. All strains were isolated from the nasal mucous membrane of patients with upper respiratory tract infection symptoms. Among the tested strains 52 were erythromycin resistant, and only 6 were erythromycin sensitive. The tested strains showed a very high percentage (89.7%) of the phenotype MLSb-constitutive resistance mechanism. The MLSb-inducible resistance among the tested strains was not observed. Association of the MLSb mechanism with resistance to chloramphenicol, trimethoprim/sulfamethoxazole and chloramphenicol, and trimethoprim/sulfamethoxazole was observed in 12.1%, 15.5%, and 44.8% tested strains, respectively. Among all isolates with the phenotype MLSb resistance, the presence of the erm(X) gene was confirmed by the polymerase chain reaction method. The results suggest that C. pseudodiphtheriticum with the MLSb-constitutive-type resistance can play a significant role in crossing this mechanism with other Corynebacterium sp., which colonize the nasal and throat mucous membrane.