Temporal flux in β-lactam resistance among Klebsiella pneumoniae in Western Australia

Our aim was to identify long-term β-lactam resistance trends in local Klebsiella pneumoniae isolates, which are a common cause of sepsis in Western Australia. We studied three collections of K. pneumoniae isolates from Western Australia between 1977 and 2015 comprising contemporary blood culture (n = 98), multiresistant (n = 21) and historical (n = 50) isolates. Antimicrobial resistance was determined by Clinical and Laboratory Standards Institute agar dilution methods. PCR DNA sequencing identified β-lactamase variants and porin mutations contributing to β-lactam resistance. Isolates were genotyped by PFGE, multilocus sequence typing and a variable number tandem repeat method. From 1989 onwards, we detected the SHV-2a extended-spectrum β-lactamase (ESBL) in ceftriaxone-resistant isolates, and in ceftazidime- and aztreonam-resistant isolates from 1993. Ceftriaxone, ceftazidime and aztreonam resistance persisted, with blaCTX-M types becoming the dominant ESBLs by 2010. CTX-M-15 was encountered in both multiresistant and blood culture isolates. Meropenem resistance was detected for the first time in 2011 in a locally isolated blaIMP-4-positive K. pneumoniae. We found sequence types ST23 and ST86 that occurred in multiple isolates from invasive infections. ST86 was the most common and maintained a high degree (90 %) of similarity by PFGE since 1977. Ceftazidime-resistant K. pneumoniae sequence types have caused invasive infections in Western Australia since 1993. Invasive isolates producing CTX-M-14 and CTX-M-15 appeared in Western Australia during the last decade, before the appearance of carbapenemases. The diversity of β-lactam resistance and β-lactamase resistance mechanisms in Western Australian K. pneumoniae has increased since ESBLs were first described locally.

The implications of endemic IMP-4 carbapenemase for clinical laboratory susceptibility testing

A local predominance of carbapenemase producing Enterobacteriaceae with low minimum inhibitory concentrations (MIC) to meropenem prompted a review of methods available for carbapenemase detection. We report on results using two selective media, temocillin discs, CarbaNP test, GeneXpert Carba-R assay and an in-house PCR assay.

Molecular epidemiology of Neisseria gonorrhoeae using multi-antigen sequence typing and pulse-field gel electrophoresis in highly endemic Western Australian populations

Background

The remote and indigenous populations of Western Australia (WA) have one of the highest notification rates of gonorrhoea in the world. Despite this, the low rate of antimicrobial resistance in Neisseria gonorrhoeae from these regions permits the use of amoxycillin as empirical therapy. We describe the first molecular epidemiological study of gonococci isolated from this population using two different typing platforms.

Methods

Pulse-field gel electrophoresis (PFGE), Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) and antimicrobial susceptibility tests were performed on 128 consecutive N. gonorrhoeae isolates cultured between January 2011 and December 2013. To highlight clusters isolates were evaluated based on their tbpB sequence types.

Results

No predominant NG-MAST or PFGE types were found. A total of 67 distinct PFGE pulsotypes were identified amongst the 128 isolates in this study with 20 PFGE pulsotypes representing 78 isolates. A total of 59 NG-MAST sequence types were found, represented by 45 porB alleles and 28 tbpB alleles with 13 tbpB genomogroups from 45 NG-MAST sequence types. TbpB genomogroup 29, represented by 45 isolates, was by far the most common genomogroup overall.

Conclusions

Results from this study suggest that gonococcal epidemiology in WA is quite different between remote regions and major population centres and, in some cases, geographically restricted. It is likely that isolates originating from endemic regions of WA mostly represent independent, small sexual networks with an infrequent interchange between other communities and regions. Given the high rate of antimicrobial resistance elsewhere in Australia, ongoing surveillance is essential to ensure the enduring efficacy of amoxycillin empiric use in the remote regions of WA.

Macrorestriction analysis of clinical and environmental isolates of Sporothrix schenckii

Sporothrix schenckii causes sporotrichosis, a disease that most commonly presents as a subacute or chronic skin infection. An unusually high incidence of clinical cases of sporotrichosis occurred in the southwest of Western Australia over the last 5 years. Anecdotal accounts from patients implicated contact with hay prior to infection. Isolates of S. schenckii from hay and clinical cases were investigated by traditional phenotypic methods and pulsed-field gel electrophoresis (PFGE). The phenotypic evaluation separated S. schenckii from Ophiostoma spp. A DNA macrorestriction method using SfiI and NotI macrorestriction digestion by PFGE was developed to investigate the epidemiological connections. BioNumerics software was used to analyze the results. DNA macrorestriction digestion patterns for the recent Western Australian clinical isolates and four hay isolates were indistinguishable. Eastern state clinical isolates, national Quality Assurance Program isolates, and other environmental isolates gave different macrorestriction patterns. Clinical isolates from the southwest of Western Australia collected in the 1980s and 1990s were also characterized using PFGE. The patterns generated were indistinguishable from those of the recent clinical isolates. PFGE showed that the dominant strain of S. schenckii causing sporotrichosis in Western Australia is present in hay, has caused sporotrichosis for at least 15 years, and is a different strain from the strains found in other parts of Australia.