Reduced susceptibility to chlorhexidine among extremely-drug-resistant strains of Klebsiella pneumoniae

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• 作者：L. Naparstek^a ; ^b ; Y. Carmeli^a ; I. Chmelnitsky^a ; E. Banin^b ; S. Navon-Venezia^a ; ^{shiri_nv@tasmc.health.gov.il}
• 关键词：XDR Klebsiella pneumoniae ; ST258 ; Extremely drug resistant ; Chlorhexidine resistance ; Heteroresistant subpopulations ; Efflux pumps
• 刊名：Journal of Hospital Infection
• 出版年：2012
• 期刊代码：177_01956701
• 类别：med
• 出版时间：May, 2012
• 卷：81
• 期：1
• 页码：15-19
• 文件大小：245 K

摘要

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Summary

Background

Over the last decade, extremely-drug-resistant (XDR) strains of Klebsiella pneumoniae have emerged worldwide, mainly as a result of patient-to-patient spread. The predominant clone, sequence type 258 (ST258), is associated with high morbidity and mortality, and is a worldwide threat to public health. It was hypothesized that reduced susceptibility to chlorhexidine, the most widely used hospital disinfectant, may contribute to the endemic nature of this strain.

Aim

To characterize and compare the susceptibility of the epidemic K.聽pneumoniae clone ST258 and non-epidemic K.聽pneumoniae clones to chlorhexidine.

Methods

The minimum inhibitory concentration (MIC) of chlorhexidine was determined in 126 XDR K.聽pneumoniae clinical isolates using agar dilution. Expression of three different efflux pumps - cepA, acrA and kdeA - was investigated in the absence and presence of chlorhexidine using quantitative real-time polymerase chain reaction. Heteroresistance to chlorhexidine was identified using population analysis.

Findings

The MIC of chlorhexidine was higher for K.聽pneumoniae ST258 (N聽=聽70) than other K.聽pneumoniae sequence types (N聽=聽56); 99%of ST258 isolates had MICs >32聽渭g/mL, compared with 52%of other K.聽pneumoniae sequence types (P聽<聽0.0001). Reduced susceptibility to chlorhexidine appeared to be independent of the expression of cepA, acrA and kdeA efflux pumps. Chlorhexidine-resistant subpopulations were observed independent of the bacterial sequence type or the MIC.

Conclusions

Reduced susceptibility to chlorhexidine may contribute to the success of XDR K.聽pneumoniae as a nosocomial pathogen, and may provide a selective advantage to the international epidemic strain K.聽pneumoniae ST258. The heterogeneous nature of chlorhexidine-resistant subpopulations suggests that this phenomenon might not be rendered genetically.