Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP) Annual Report 2015

From 1 January to 31 December 2015, 31 Australian institutions participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aim of ASSOP 2015 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that are antimicrobial resistant, with particular emphasis on susceptibility to methicillin and to characterise the molecular epidemiology of the methicillin-resistant isolates. Overall 18.2% of the 2,399 SAB episodes were methicillin-resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 18.8% which was not significantly higher than the 15.1% mortality associated with methicillin-sensitive SAB. With the exception of the ss-lactams and erythromycin, antimicrobial resistance in methicillin sensitive S. aureus (MSSA) remains rare. However, in addition to the ss-lactams, approximately 50% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin and ciprofloxacin and approximately 15% resistant to co-trimoxazole, tetracycline and gentamicin. When applying the EUCAST breakpoints teicoplanin resistance was detected in two S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA clones; ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). ST22-IV [2B] (EMRSA-15) is the predominant healthcare-associated clone in Australia. Sixty-seven percent of methicillin-resistant SAB were due to community-associated clones. Although polyclonal, almost 43% of community-associated clones were characterised as ST93-IV [2B] (Queensland CA-MRSA) and ST1-IV [2B] (WA1). CA-MRSA in particular the ST45-V [5C2&5] (WA84) clone has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. As CA-MRSA is well established in the Australian community it is important antimicrobial resistance patterns in community and health-care-associated SAB are monitored as this information will guide therapeutic practices in treating S. aureus sepsis.