High-level aminoglycoside resistance among enterococd and group A streptococci

The occurrence of high-level aminoglycoside resistance (HLAmR) was determined for 73 enterococci and 54 group A streptococci by the high-load disc method, tube macrodilution and the porymerase chain reaction (PCR). The PCR method revealed the presence of genes coding for aminoglycoside-3'-0-phosphoryltransfcrasc-III (APH(3>m), ammoglycoside-6'-^-acetyltransferase/2"-0-phosphoryltransferasc (AACtfO/APHfr)), or both, in 20-6%, 9-6 % and 4-1 % of the enterococci, respec-tively. The prevalence of HLAmR to at least one aminoglycoside among local enterococci was 37 % (27/73). Only one of 54 Streptococcus pyogenes isolates produced APH(3>m and exhibited high-level resistance to kanamyrin and strepto-mycin. In general, the three methods yielded comparable results, with only three discrepancies among the 127 isolates examined. High-load disc screening and tube macrodilution proved to be practical, reliable and reproducible, and thus suitable for routine screening. Of 20 Enterococcus faecalis strains tested, all were penicillin-tolerant. Only one of seven penicillin-tolerant S. pyogenes strains was HLAmR. No association between the two forms of resistance was found