title: Susceptibility to antimicrobial agents and analysis of plasmids in gentamicin- and methicillin-resistant Staphylococcus aureus from Dublin hospitals.
abstract: Methicillin- and gentamicin-resistant Staphylococcus aureus (MGRSA) strains isolated from Dublin Hospitals were classified into two groups (phenotypes). Phenotype-I strains expressed high level resistance to gentamicin and were susceptible to fusidic acid; strains resistant to tetracycline harboured a 3 X 10(6)-mol. wt plasmid. Strains in phenotype II usually expressed low level resistance to gentamicin, were resistant to fusidic acid and often harboured a (22-24) X 10(6)-mol. wt plasmid that specified resistance to ethidium bromide, tetracycline, kanamycin, neomycin and trimethoprim, or to combinations of these markers. A few phenotype-II strains expressed higher levels of resistance to gentamicin and other aminoglycosides. All MGRSA strains carried a 21 X 10(6)-mol. wt plasmid conferring resistance to penicillin, ethidium bromide, cadmium and mercury. Gentamicin resistance was invariably chromosomal and all strains carried chromosomal resistance to methicillin, erythromycin, streptomycin and spectinomycin. Several methicillin-resistant S. aureus (MRSA) strains isolated before the emergence of gentamicin resistance harboured a 21 X 10(6)-mol. wt penicillinase plasmid with the same restriction endonuclease profile as that from some MGRSA strains. Some MRSA strains carried other plasmids related to those found in MGRSA strains.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001434:Bacteriophage Typing; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000032:analysis; D004996:Ethidium / Q000494:pharmacology; D005839:Gentamicins / Q000494:pharmacology*; D006801:Humans; D007494:Ireland; D008712:Methicillin / Q000494:pharmacology*; D010403:Penicillin Resistance; D011815:R Factors; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D014169:Transformation, Bacterial
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D005839:Gentamicins; D004262:DNA Restriction Enzymes; D004996:Ethidium; D008712:Methicillin