Antibiotic susceptibilities and plasmid profiles of nosocomial methicillin-resistant Staphylococcus aureus: A retrospective study

M. T. Gillespie, J. W. May, R. A. Skurray

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Methicillin-resistant Staphylococcus aureus strains isolated at a single Melbourne Hospital between 1969 and 1981 were examined for susceptibility to a range of antimicrobial agents and for the presence of plasmid DNA. Isolates obtained during 1969 possessed a plasmid of mol. wt 20 x 106, encoding heavy metal resistance and penicillinase production, and a plasmid of mol. wt 2.8 x 106, mediating tetracycline resistance. In the majority of isolates obtained after 1973, these functions were chromosomally encoded. Before 1980, both high- and low-level chromosomally-encoded gentamicin resistances were encountered, whereas isolates from 1980 and 1981 displayed low-level gentamicin resistance only; the latter phenotype was most commonly mediated by a plasmid of mol. wt 18 x 106 that also encoded resistance to tobramycin and kanamycin. Chloramphenicol resistance in strains isolated throughout the period was mediated by one of three plasmids, each of mol. wt c. 3 x 106.

Original languageEnglish
Pages (from-to)295-310
Number of pages16
JournalJournal of Medical Microbiology
Issue number3
Publication statusPublished - 1 Jan 1984

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