DETERMINATION OF PRESENCE OF RESISTANCE TO ERYTHROMYCIN AND TETRACYCLINE ANTIBIOTICS IN ISOLATED STREPTOCOCCUS SPECIES FROM GROUP C AND GROUP G

The purpose of this study was to determine the presence of resistance to macrolide and tetracycline in _-haemolytic streptococci which belong to group C (GCS) and group G (GGS), isolated from variuos clinical specimens collected at the Institute of Public Health of Serbia during the period 2006-2008. After determination of resistance in isolated streptococci to tested antibiotics, their phenotypic and genotypic characteristics were investigated. Resistance to erythromycin and tetracycline were evaluated in a total of 112 GGS and 29 GCS isolates. Resistance to erythromycin was determined in 6 (6.9%) GGS isolates and 4 of them were also resistant to tetracycline. Resistance to erythromycin was determined in 2 (5.4%) GCS isolates, but both isolates were sensitive to tetracycline. The erythromycinresistance phenotypes were determined by the double-disk test with erythromycin and clindamycin disks. All 8 isolates showed the MLSB macrolide resistance phenotype leading to macrolide, lincosamide and streptogramin B resistance. These 8 isolates were genotyped for the presence of the erm(TR), erm(B), mef(A) and tet(M) genes and transposon of the Tn916-Tn1545 family by polymerase chain reaction. The presence of erm(TR) gene was detected in 3 GGS isolates and in both GCS isolates, while the presence of erm(B) gene was detected in other 3 GGS isolates. The presence of tet(M) gene with transposon of the Tn916-Tn1545 family was detected in all 4 tetracycline-resistant GGS isolates. The results of this study indicate that continued monitoring of macrolide- and tetracycline- resistance in tested groups of streptococci in Belgrade and in Republic of Serbia is necessary.