Transcriptional expression of PmrB and arnA within polymyxin-resistant nosocomial isolates of Pseudomonas aeruginosa from India

Abstract

Objective: The polymyxin group of antibiotics is considered to be one of the most effective antimicrobial agents against many serious pathogenic bacteria, but the excessive use of these antibiotics has led to the development of drug resistance among bacteria. This study was designed to characterize polymyxin-resistant P. aeruginosa and to explore the role of PmrB and arnA in resistant phenotype. Methods: mRNA and cDNA of five selected polymyxin-resistant strains representing different MIC range; isolated under normal condition of strain growth, after treating sample/media with FeCl3 and MgCl2 alone, or after treating with FeCl3 and polymyxin antibiotic. The transcriptional expression was observed for PmrB and arnA by quantitative real time RT-PCR in reference to P. aeruginosa PAO1. The presence of plasmid mediated colistin resistance determinants mcr-1 was screened by PCR. Susceptibility of the strains was determined by disc-diffusion method and DNA fingerprinting was carried out by performing REP-PCR. Results: A down regulated expression of PmrB and arnA was observed even after the unique induction with FeCl3 and MgCl2. All the isolates were found to be resistant against cefepime and different clonal patterns of resistance were found among the isolates. Conclusion: This study has drawn a new insight into polymyxin resistance which will help in the detection and control of infections caused by multidrug resistant P. aeruginosa. The low susceptibility rate to aminoglycoside, piperacllin-tazobactam and ciprofloxacin was found and in addition, detection of PmrB and arnA as molecular markers in the follow up of infections caused by multidrug resistant P. aeruginosa.

Pseudomonas aeruginosa transcriptome analysis in a cystic fibrosis lung model reveals metabolic changes accompanying biofilm maturation and increased antibiotic tolerance over time

“…The brc-1 gene, which encodes a major facilitator superfamily (MFS) transporter associated with bicyclomycin resistance [25], was significantly underexpressed from 24 h to 7 d. The other two significant DEGs found were significantly underexpressed from 24 h to 48 h. This included mexG and arnA , which encode a transmembrane protein associated with multiple efflux pumps and a bifunctional UDP-glucuronic acid decarboxylase/UDP-4-amino-4-deoxy-L-arabinose formyltransferase [3], respectively. More specifically, the enzyme encoded by arnA is involved in lipid A modifications, linked to cationic antimicrobial peptide (CAMP) resistance [26, 27].…”

“…The brc-1 gene, which encodes a major facilitator superfamily (MFS) transporter associated with bicyclomycin resistance [25], was significantly underexpressed from 24 h to 7 d. The other two significant DEGs found were significantly underexpressed from 24 h to 48 h. This included mexG and arnA, which encode a transmembrane protein associated with multiple efflux pumps and a bifunctional UDP-glucuronic acid decarboxylase/UDP-4-amino-4-deoxy-L-arabinose formyltransferase [3], respectively. More specifically, the enzyme encoded by arnA is involved in lipid A modifications, linked to cationic antimicrobial peptide (CAMP) resistance [26,27]. To determine how AMR gene expression compared to phenotype, P. aeruginosa PA14 was grown as a biofilm on the EVPL tissue for 24 h, 48 h or 7 d then exposed to one of two clinically relevant polymyxins, polymyxin B or colistin, for a further 24 h. The CFU lung -1 was determined and compared with PA14 EVPL biofilms treated with phosphate-buffered saline (PBS) for the second 24 h incubation as a negative control (Figure 5).…”