These data confirm the potent in vitro activity of fidaxomicin against C. difficile. Moreover, this study provides an important baseline for ongoing long-term surveillance of antimicrobial resistance and prospective tracking of prominent and emerging strain types.

Emergence and spread of predominantly communityonset Clostridium difficile PCR ribotype 244 infection in Australia, 2010 to 2012 D W Eyre (david.eyre@ndm.ox.ac.

Pseudomonas aeruginosa are noscomially acquired, opportunistic pathogens that pose a major threat to the health of burns patients and the immunocompromised. We sequenced the genomes of P. aeruginosa isolates RNS_PA1, RNS_PA46 and RNS_PAE05, which displayed resistance to almost all frontline antibiotics, including gentamicin, piperacillin, timentin, meropenem, ceftazidime and colistin. We provide evidence that the isolates are representatives of P. aeruginosa sequence type (ST) 235 and carry Tn6162 and Tn6163 in genomic islands 1 (GI1) and 2 (GI2), respectively. GI1 disrupts the endA gene at precisely the same chromosomal location as in P. aeruginosa strain VR-143/97, of unknown ST, creating an identical CA direct repeat. The class 1 integron associated with Tn6163 in GI2 carries a blaGES-5–aacA4–gcuE15–aphA15 cassette array conferring resistance to carbapenems and aminoglycosides. GI2 is flanked by a 12 nt direct repeat motif, abuts a tRNA-gly gene, and encodes proteins with putative roles in integration, conjugative transfer as well as integrative conjugative element-specific proteins. This suggests that GI2 may have evolved from a novel integrative conjugative element. Our data provide further support to the hypothesis that genomic islands play an important role in de novo evolution of multiple antibiotic resistance phenotypes in P. aeruginosa.

Objectives In the early 2000s, a binary toxin (CDT)-producing strain of Clostridium difficile, ribotype (RT) 027, caused extensive outbreaks of diarrhoeal disease in North America and Europe. This strain has not established in Australia and there is a markedly different repertoire of circulating strains compared to other regions of the world. The C. difficile Antimicrobial Resistance Surveillance (CDARS) study is a nationwide longitudinal surveillance study of C. difficile infection (CDI) in Australia. Here, we describe the molecular epidemiology of CDI in Australian healthcare and community settings over the first 5 years of the study, 2013–2018. Methods Between 2013 and 2018, 10 diagnostic microbiology laboratories from five States in Australia participated in the CDARS study. From each of five states, one private (representing community) and one public (representing hospitals), submitted isolates of C. difficile or PCR-positive stool samples during two collection periods per year, February-March (summer/autumn) and August-September (winter/spring). C. difficile was characterised by toxin gene profiling and ribotyping. Results A total of 1523 isolates of C. difficile was studied. PCR ribotyping yielded 203 different RTs, the most prevalent being RT014/020 (n=449, 29.5%). The epidemic CDT+ RTs 027 (n=2) and 078 (n=6), and the recently described RTs 251 (n=10) and 244 (n=6) were not common, while RT126 (n=17) was the most prevalent CDT+ strain. Conclusions A heterogeneous C. difficile population was identified. C. difficile RT014/020 was the most prevalent strain found in humans with CDI. Continued surveillance of CDI in Australia remains critical for the detection of emerging strain lineages.

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