A national survey of antimicrobial resistance in Staphylococcus aureus in Australian teaching hospitals

Abstract

An extensive survey of the in-vitro susceptibility of clinical isolates of Staphylococcus aureus to 18 antimicrobial agents was conducted over three separate periods during 1986-1987 in 14 teaching hospitals in major Australian cities. The survey aimed to document the prevalence of resistance to a wide variety of drugs that are important as antistaphylococcal agents or as epidemiological markers. More than 7500 isolates were examined. Nationally, the prevalence of resistance was 85.3% to penicillin G, 14.4% to methicillin, 14.0% to amoxycillin/clavulanate, 9% to cephalothin, 5.4% to cephamandole, 9.9% to cefotaxime, 25.0% to erythromycin, 11.2% to clindamycin, 21.7% to tetracycline, 13.0% to gentamicin, 1.9% to amikacin, 5.8% to chloramphenicol, 18.3% to trimethoprim, 0.6% to rifampicin, 3.0% to fusidic acid and 1.2% to novobiocin. For none of the strains was resistance to vancomycin confirmed by minimal-inhibitory-concentration determination. A high proportion of the resistances was harboured in methicillin-resistant Staph. aureus, except for resistance to penicillin G, erythromycin and tetracycline. The prevalence of methicillin resistance varied widely among the states: 25.2% in Queensland, 23.5% in Victoria, 12.6% in New South Wales/the Australian Capital Territory, 11.3% in South Australia and 0.4% in Western Australia. Isolates from blood cultures were slightly-more susceptible to antimicrobial agents than were isolates from other body sites. Six common profiles of resistance to penicillin G, methicillin, erythromycin, clindamycin and tetracycline accounted for more than 95% of the isolates that were tested against all five agents. Vancomycin remains the most important antistaphylococcal drug in areas where resistance to methicillin is common.