Australian Group on Antimicrobial-resistance (AGAR) Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP) Annual Report 2016

From 1st January to 31st December 2016, 32 institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aim of ASSOP 2016 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. A total of 2,540 S. aureus bacteraemia episodes were reported, of which 19.7% were methicillin-resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 23.1% which was significantly higher than the 15.3% mortality associated with methicillin-susceptible SAB. With the exception of the ss-lactams and erythromycin, antimicrobial-resistance in methicillin-susceptible S. aureus (MSSA) was rare. However, in addition to the ss-lactams approximately 45% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin and ciprofloxacin and approximately 14% 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-betalactam antimicrobials was largely attributable to 2 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. Seventy two percent of methicillin-resistant SAB were due to community associated clones. Although polyclonal almost 60% of community associated clones were characterised as ST93-IV [2B] (Queensland CA-MRSA), ST5-IV [2B] and ST1-IV [2B]. CA-MRSA in particular the ST45-V-T [5C2&5] clone has acquired multiple antimicrobial-resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. Twelve percent of CA-MRSA were ST45-V-T [5C2&5]. As CA-MRSA is well established in the Australian community it is important antimicrobial-resistance patterns in community- and healthcare-associated SAB is monitored as this information will guide therapeutic practices in treating S. aureus sepsis.