High-level aminoglycoside resistance among enterococci and group A streptococci

Abstract

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 polymerase chain reaction (PCR). The PCR method revealed the presence of genes coding for aminoglycoside-3'-O-phosphoryltransferase-III (APH(3')-III), aminoglycoside-6'-N-acetyltransferase/2''-O-phosphoryltransferase (AAC(6')/APH(2'')), or both, in 20.6%, 9.6% and 4.1% of the enterococci, respectively. 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')-III and exhibited high-level resistance to kanamycin and streptomycin. 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.

Molecular Detection of Antimicrobial Resistance

“…A study (369) of the presence of high-level aminoglycoside resistance in 73 enterococci and 54 group A streptococci compared a high-load disk method, tube macrodilution, and PCR. Only one streptococcal isolate displayed high-level resistance to streptomycin and kanamycin; PCR revealed the presence of the aphA3 gene.…”

Six-Month Multicenter Study on Invasive Infections Due to Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis in Argentina

“…High-level resistance to aminoglycosides has been described in a few isolates of S. pyogenes and groups G and C S. dysgalactiae subsp. equisimilis (9,33).…”

Identification of Aminoglycoside-Modifying Enzymes by Susceptibility Testing: Epidemiology of Methicillin-Resistant Staphylococcus aureus in Japan

“…However, characterizing strains containing several AME genes solely on the basis of aminoglycoside resistance profiles can be difficult, since one resistance profile is often partially duplicated thereby masking the presence of an additional profile. DNA hybridization and PCR amplification are sensitive and specific methods for the detection of genes including those encoding AME (34,36,38). However, such special techniques and the necessary equipment are not practical for the routine clinical laboratory, unlike conventional susceptibility tests.…”