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J Med Microbiol. 2016 May;65(5):429-437. doi: 10.1099/jmm.0.000242. Epub 2016 Mar 4.

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

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1The Marshall Centre for Infectious Diseases, School of Pathology and Laboratory Medicine, University of Western Australia,Nedlands, Western Australia,Australia.
2PathWest Laboratory Medicine, Fiona Stanley Hospital,Murdoch, Western Australia,Australia.
3PathWest Laboratory Medicine, QEII Medical Centre,Nedlands, Western Australia,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.


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