Affiliation:
1. Department of Microbiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555,1 and
2. Laboratory of Drug Resistance in Bacteria, Gunma University School of Medicine, 3-39-22 Showamachi, Maebashi, Gunma 371-8511,2Japan
Abstract
ABSTRACT
A multiple-primer PCR was used to identify genes encoding aminoglycoside-modifying enzymes in 381 clinical isolates of methicillin-resistant
Staphylococcus aureus
(MRSA). The technique used three sets of primers delineating specific DNA fragments of the
aph(3′)-III, ant(4′)-I
, and
aac(6′)-aph(2")
genes, which influence the MICs of gentamicin, tobramycin, and lividomycin. Isolates with none of the three genes detected were susceptible to all three agents. Isolates with the
aph(3′)-III
gene showed resistance to lividomycin (MIC > 1,024 μg/ml), and those with the
ant(4′)-I
gene were resistant to tobramycin (MIC ≥ 8 μg/ml). Isolates with only the
aac(6′)-aph(2")
gene were resistant to gentamicin (MIC ≥ 8 μg/ml) and tobramycin in decreasing order; those with both the
ant(4′)-I
and
aac(6′)-aph(2")
genes also were resistant to gentamicin and tobramycin, but in increasing order. Susceptibility testing, then, could detect specific genes. In 381 Japanese MRSA isolates, the
ant(4′)-I, aac(6′)-aph(2")
, and
aph(3′)-III
genes were prevalent in 84.5, 61.7, and 8.9%, respectively. Isolates with only the
ant(4′)-I
gene had coagulase type II or III, but isolates with both the
ant(4′)-I
and
aac(6′)-aph(2")
genes included all coagulase types. Most isolates with coagulase type IV or VII carried the
aac(6′)-aph(2")
gene. Of the MRSA isolates with
ant(4′)-I
and/or
aac(6′)-aph(2")
genes, 97% were resistant to aminoglycosides in clinical use, but a new aminoglycoside, arbekacin, had excellent activity against these isolates.
Publisher
American Society for Microbiology
Cited by
110 articles.
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