In Vivo Evolution to Colistin Resistance by PmrB Sensor Kinase Mutation in KPC-Producing Klebsiella pneumoniae Is Associated with Low-Dosage Colistin Treatment

Abstract

e Colistin is a key drug for the treatment of infections caused by extensively drug-resistant strains of Enterobacteriaceae producing carbapenemases. However, the emergence of colistin resistance is being increasingly reported, especially among Klebsiella pneumoniae strains producing KPC-type carbapenemases (KPC-KP). In this work, we investigated colistin-susceptible (KPB-1) and colistin-resistant (KPB-2) sequential isolates obtained from a patient with a KPC-KP infection before and after low-dosage colistin treatment, respectively. By using a next-generation sequencing approach and comparative genomic analysis of the two isolates, we detected in KPB-2 a nonsynonymous nucleotide substitution in the gene encoding the PmrB sensor kinase, resulting in a leucine-to-arginine substitution at amino acid position 82. Compared with KPB-1, KPB-2 exhibited upregulated transcription of pmrA and of pmrK, which is part of the pmrHFIJKLM operon responsible for modification of the colistin lipopolysaccharide target. Complementation with wild-type pmrB in KPB-2 restored colistin susceptibility and reduced the transcription of pmrA and pmrK to basal levels, while expression of PmrB L82R in KPB-1 did not alter colistin susceptibility or upregulate pmrA and pmrK expression, confirming the dominance of wild-type PmrB versus the PmrB L82R mutant. The present results indicated that PmrB mutations mediating colistin resistance may be selected during low-dosage colistin treatment. The colistin-resistant phenotype of KPB-2 was stable for up to 50 generations in the absence of selective pressure and was not associated with a significant fitness cost in a competition experiment.

Colistin Resistance Mechanisms in Klebsiella pneumoniae Strains from Taiwan

“…1). As in previous studies (18,20,21,32,33), the mgrB region of these 8 strains was interrupted by IS10R and IS5-like elements. To demonstrate an effect on mgrB expression after IS element insertion in the promoter, the expression of mgrB mRNA was quantified by RT-qPCR, and the expression of mgrB was significantly reduced in those 5 strains (Table 1).…”

Tracking Nosocomial Klebsiella pneumoniae Infections and Outbreaks by Whole-Genome Analysis: Small-Scale Italian Scenario within a Single Hospital

“…The entire set of pmr genes was highly conserved among the 16 strains, including the pmrB locus, which has been indicated as a colistin resistance determinant (42). All colistin-resistant strains harbored a variant of the mgrB gene interrupted by an IS5-like transposon ( Table 3).…”

Correlation of β-Lactamase Production and Colistin Resistance among Enterobacteriaceae Isolates from a Global Surveillance Program

“…Several species of Enterobacteriaceae are naturally resistant to polymyxin derivatives, including Proteeae and Serratia spp., and studies have documented a higher prevalence of these pathogens following the increasing usage of colistin, which was associated with high mortality rates (16,17). A recent study documented the in vivo evolution of a KPC-producing Klebsiella pneumoniae isolate to a stable colistin-resistant phenotype following low-dosage colistin use (13), and colistin heteroresistance among Enterobacteriaceae isolates following colistin therapy has also been reported (18). In addition to these resistance issues, related toxicity issues are also a concern (19).…”

“…It can be due to modifications of lipid A that alter the net charge of the cellular lipopolysaccharide (LPS), thereby reducing its affinity for polymyxins (12). In addition, mutations that activate the PhoPQ and PmrAB two-component signal transduction systems that regulate LPS modification, including alterations of the negative regulator encoded by mgrB, have been reported (12)(13)(14)(15). Several species of Enterobacteriaceae are naturally resistant to polymyxin derivatives, including Proteeae and Serratia spp., and studies have documented a higher prevalence of these pathogens following the increasing usage of colistin, which was associated with high mortality rates (16,17).…”