Association between disinfectant resistance genes in exoU and exoS Pseudomonas aeruginosa with sensitivity to multipurpose disinfecting solutions and antibiotics.

Abstract

Background: The aim of this study was to determine differences in susceptibility of exoU and exoS Pseudomonas aeruginosa to multi-purpose disinfecting solutions (MPDS) and antibiotics and their association with disinfectant resistance genes.

Methods: A total of 16 exoU and 24 exoS P. aeruginosa keratitis isolates were tested for susceptibility against four multipurpose disinfecting solutions (OPTI-FREE PureMoist, Acuvue RevitaLens, Biotrue, and Renu Advanced Formula) using minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations. Antibiotic susceptibility to ciprofloxacin, levofloxacin, gentamicin, and tobramycin was determined by MIC. Whole genome sequences from 27 isolates were utilized to identify disinfectant resistance genes and single nucleotide polymorphisms (SNPs) in the genes using the Comprehensive Antibiotic Resistance Database (CARD) and Geneious Prime respectively. Polymerase chain reaction (PCR) was used to detect the disinfectant resistance genes qacE, qacEΔ1, and sugE1. Correlation between disinfectant resistance genes and their SNPs with disinfectant and antibiotic MICs was determined by Spearman's Rho.

Results: All MPDS were bactericidal at full strength, but upon dilution OPTI-FREE Puremoist and Renu Advanced Formula were the most active against the exoU and exoS groups correspondingly. ExoU showed significantly higher resistance than exoS (p ≤ 0.04) to levofloxacin (37.5 % vs. 8.3 %), gentamicin (43.8 % vs. 0 %), and tobramycin (37.5 % vs. 0 %). The qacEΔ1 and sugE1 genes along with several SNPs in the resistance genes were more common in the exoU group. SNPs in disinfectant resistance genes correlated with MPDS MICs/MBCs, notably mexQ Arg1036His (R ≥ -0.38, p ≤ 0.04), Gly505Asp (R ≥ 0.40, p ≤ 0.04) and opmD Gly269Ser (R ≥ 0.43, p ≤ 0.03). QacEΔ1 and sugE1 were linked to increased MIC (R ≥ 0.54, p < 0.01) and MBC (R ≥ 0.50, p < 0.01) for Renu Advanced Formula. Also, multiple SNPs and qacEΔ1 and sugE1 showed moderate to large positive associations with antibiotic resistance.

Conclusions: ExoU strains had distinct MPDS susceptibility patterns, with higher disinfectant resistance genes prevalence and mutations, contributing to MPDS and antibiotics resistance.