Ida T, Okamoto R, Shimauchi C, Okubo T, Kuga A, Inoue M. Identification of aminoglycoside-modifying enzymes by susceptibility testing: epidemiology of methicillin-resistant Staphylococcus aureus in Japan.
J Clin Microbiol 2001;
39:3115-21. [PMID:
11526138 PMCID:
PMC88306 DOI:
10.1128/jcm.39.9.3115-3121.2001]
[Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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 microg/ml), and those with the ant(4')-I gene were resistant to tobramycin (MIC > or = 8 microg/ml). Isolates with only the aac(6')-aph(2") gene were resistant to gentamicin (MIC > or = 8 microg/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.
Collapse