[Aminoglycosides resistance of methicillin-resistant Staphylococcus aureus].
In the last decade, there has been a dramatic increase in the isolation frequency of methicillin-resistant Staphylococcus aureus (MRSA) in Japan. Especially, a high incidence of multiple resistant MRSA strains has been reported. These strains are resistant not only to beta-lactams but to aminoglycosides and macrolides. About 90% of MRSA strains were resistant to gentamicin (GM) and/or tobramycin (TOB), producing an aminoglycoside modifying enzyme, mainly, APH (2")/AAC (6) and/or AAD (4',4"). Based on these modifying enzymes produced, MRSA strains were classified into three groups; group 1 produced APH (2")/AAC (6), belonging to phage group I and coagulase IV, group 2 produced AAD (4',4"), belonging to phage group III and coagulase II, and group 3 produced APH (2")/AAC (6) and AAD (4',4"), belonging to phage group III and coagulase II. The epidemiological results suggest that MRSA strains changed from group 1 to group 2, and then to group 3. Recently, arbekacin (ABK), a new anti-MRSA aminoglycoside, has been introduced into clinical practice. ABK shows a potent activity to GM-resistant strains, due to poorly modification by APH (2")/AAC (6'). However, there were few ABK- and GM-resistant strains in clinical isolates. These strains produced a higher amount of the enzyme than ABK-susceptible and GM-resistant strains. This observation suggests that ABK-resistant strains might be derived from GM-resistant strains by mutation of the gene coding APH (2")/AAC (6').
Okamoto
R
R
Laboratory of Drug Resistance in Bacteria, Gunma University School of Medicine.
Okubo
T
T
D000123:Acetyltransferases / Q000378:metabolism; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016106:Methicillin Resistance; D009713:Nucleotidyltransferases / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000123:Acetyltransferases; D010770:Phosphotransferases; D009713:Nucleotidyltransferases; C020658:glutamine-synthetase adenylyltransferase