Division of Microbiology, Calgary Laboratory Services, Calgary, Alberta, Canada.
J Antimicrob Chemother. 2012 May;67(5):1114-20. doi: 10.1093/jac/dks026. Epub 2012 Feb 14.
A study was designed to investigate the molecular epidemiology of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae isolated in a centralized region over a 10 year period (2000-09).
Molecular characterization was done using isoelectric focusing, PCR and sequencing for bla(CTX-M), bla(TEM) and bla(SHV) genes and plasmid-mediated quinolone resistance determinants. Genetic relatedness was determined with PFGE using XbaI and multilocus sequencing typing.
A total of 89 patients with incident infections were identified; the majority presented with hospital-onset urinary tract infections. The absolute number of ESBL-producing isolates remained very low until 2003, increased slightly in 2004, remained stable until 2008 and then in 2009 there was an abrupt increase in the numbers of ESBL producers identified. The majority of K. pneumoniae produced CTX-M-14 and -15, and have replaced SHV-12-producing isolates since 2005. We identified four different major sequence types (STs) among 32% of isolates (i.e. ST17, ST20, and the new ST573 and ST575) and provided insight into their clinical and molecular characteristics. The ST isolates were more likely to produce community-onset infections, were associated with bla(CTX-M) and emerged during the latter part of the study period. ST17 produced CTX-M-15 and SHV-12, and was more likely to be positive for qnrB; ST20 produced CTX-M-14 and was positive for qnrS. The multiresistant ST575 that produced CTX-M-15 appeared in 2009.
Our study highlights the importance of molecular epidemiology in providing insight into the emergence, characteristics and distribution of STs among ESBL-producing K. pneumoniae.
本研究旨在调查在一个集中区域的 10 年（2000-09 年）期间分离的产超广谱β-内酰胺酶（ESBL）的肺炎克雷伯菌的分子流行病学。
采用等电聚焦、PCR 和测序方法对 bla（CTX-M）、bla（TEM）和 bla（SHV）基因和质粒介导的喹诺酮耐药决定因子进行分子特征分析。通过 XbaI 和多位点序列分型的 PFGE 确定遗传相关性。
共鉴定出 89 例有感染事件的患者，大多数为医院获得性尿路感染。直到 2003 年，产 ESBL 分离株的绝对数量仍然很低，2004 年略有增加，直到 2008 年保持稳定，然后在 2009 年，鉴定出的产 ESBL 数量突然增加。大多数肺炎克雷伯菌产生 CTX-M-14 和 -15，自 2005 年以来已取代 SHV-12 产生的分离株。我们在 32%的分离株中发现了 4 种不同的主要序列类型（ST）（即 ST17、ST20 以及新的 ST573 和 ST575），并深入了解了它们的临床和分子特征。ST 分离株更可能引起社区获得性感染，与 bla（CTX-M）相关，并在研究后期出现。ST17 产生 CTX-M-15 和 SHV-12，更可能对 qnrB 呈阳性；ST20 产生 CTX-M-14，对 qnrS 呈阳性。2009 年出现了多耐药 ST575，该型产生 CTX-M-15。
本研究强调了分子流行病学在提供有关产 ESBL 肺炎克雷伯菌 ST 出现、特征和分布的见解方面的重要性。
