Chlorhexidine exposure of clinical Klebsiella pneumoniae strains leads to acquired resistance to this disinfectant and to colistin

• Published in: International journal of antimicrobial agents 2019-06, Vol.53 (6), p.864-867
• Main Authors: Zhang, Yizhi, Zhao, Yajie, Xu, Chunquan, Zhang, Xiucai, Li, Jiahui, Dong, Guofeng, Cao, Jianming, Zhou, Tieli
• Format: Article
• Language: English
• Subjects: Adaptive resistance; Chlorhexidine; Colistin; Cross-resistance; Fitness; Klebsiella pneumoniae
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2019.02.012

•Three K. pneumoniae isolates were cultured with increasing chlorhexidine concentrations to assess acquired resistance.•Increased resistance to chlorhexidine and colistin after exposure to increasing chlorhexidine concentrations was observed.•The main mechanism of adaptive resistance was probably hyperexpression of cepA encoding an efflux pump.•An amino acid substitution in PmrB was responsible for cross-resistance to colistin. Chlorhexidine is widely used as a disinfectant in hospitals, which may impose a selective pressure on bacteria. This study aimed to determine whether continuous exposure to chlorhexidine could lead to adaptive resistance and cross-resistance as well as investigating potential resistance mechanisms. Three clinical Klebsiella pneumoniae strains susceptible to conventional antimicrobials were selected and were continuously cultured in broth with gradually increasing concentrations of chlorhexidine. Antimicrobial susceptibility was determined. Mechanisms of acquired resistance to chlorhexidine and colistin were analysed by PCR and reverse transcription quantitative PCR (RT-qPCR). Furthermore, fitness was assessed through growth curve assays. Increased resistance to chlorhexidine and colistin was observed in all strains. Expression of the cepA gene was upregulated in the adapted strains, suggesting that hyperexpression of CepA was probably the main mechanism of adaptive resistance to chlorhexidine. The amino acid substitutions Leu82Arg and Arg256Gly in PmrB were detected in all of the adapted strains, whilst Leu344Pro was only identified in one adapted strain, indicating that the PmrB substitution was responsible for the cross-resistant phenotype. Moreover, chlorhexidine adaptation might have an effect on bacterial growth.