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Molecular epidemiology of tetracycline resistance among viridians group streptococci isolated from various clinical specimens

Viridans Group Streptococci (VGS) are inhabitant of normal oropharyngeal, urogenital tract and gastrointestinal tract and also considered as both commensals as well as pathogen. VGS causes serious infections which include septicemia, Infective Endocarditis (IE), meningitis and sepsis in neutropenic patients. Even though, tetracycline is occasionally used, resistance among VGS against this antibiotic has been well documented. All 106 VGS isolates were tested for tetracycline resistance by MIC. Detection of tetracycline (tet (M), tet (K), tet (L), tet (O)) resistance genes were performed by PCR. Thirty two out of 106 isolates were found to be resistant to tetracycline by MIC. Among the 32 tetracycline resistant isolates, 14 (43.75%) isolates amplified tet (M) gene, 3 (9.38%) isolates amplified tet (O) gene, 1 (3.12%) isolate amplified tet (M) and tet (O) genes, 1 (3.12%) isolate was positive for tet (M) and tet (L) genes. Among the resistance genes present, tet (M) was the most predominant gene reported in our isolates. The relationship of tet (M) gene with the conjugative transposons which are responsible for the dissemination of various resistance genes warrants a periodical surveillance of this gene, which may serve as an indicator for the dissemination of other resistance genes among VGS and other Streptococcus sp.

Author(s): Jin-qi Sun, Lei Li, Kai Zhao, Lei-feng Zhang, Heng-tao Ji, Yan-xia He