Coexistence of multidrug resistance mechanisms and virulence genes in carbapenem-resistant Pseudomonas aeruginosa strains from a tertiary care hospital in South India.

OBJECTIVES: This study aimed to identify the multiple drug resistance mechanisms and various virulence genes in high-level carbapenem-resistant Pseudomonas aeruginosa (CARPA) isolates collected from patients hospitalised in a tertiary care hospital in South India.

METHODS: A total of 156 CARPA isolates were included in the study. Multiplex PCR was optimised to detect carbapenemase and extended-spectrum β-lactamase (ESBL) genes. Semi-quantitative reverse transcription PCR (RT-PCR) was optimised to evaluate oprD deficiency. Efflux pump activity was determined by phenylalanine-arginine β-naphthylamide (PAβN) assay, and expression of mexA and mexC genes was evaluated by real-time quantitative PCR (qRT-PCR). Presence of the virulence genes exoS, algD, algU, lasR and rhlR were detected by qRT-PCR and plcH and lasB by RT-PCR.

RESULTS: Genes encoding carbapenemases and ESBLs were detected in 48.7% (blaVIM, 23.1%; blaNDM-1, 17.3%; blaVIM+blaNDM-1, 7.1%; and blaIMP, 1.3%) and 4% (blaVEB, 4.5%) of CARPA isolates, respectively. Loss of porin OprD was observed in nine isolates (5.8%), two of which harboured the blaVIM gene. Among efflux pump-positive isolates, mexA expression was significantly upregulated. algD expression was detected in 93% of CARPA isolates, followed by algU (89%), rhlR (84%), lasR (81%) and exoS (76%). The lasB and plcH genes were detected in 94% and 92% of isolates, respectively.

CONCLUSIONS: Co-existence of multiple antimicrobial resistance mechanisms together with virulence genes in carbapenem-resistant isolates has become an alarming emerging threat. Continuous monitoring of multidrug-resistant pathogens is important for clinicians in order to determine therapeutic options against such infections.