Triclosan Tolerance Is Driven by a Conserved Mechanism in Diverse <i>Pseudomonas</i> Species

Abstract

Perturbation of natural microbial communities by antimicrobials, such as triclosan, can result in selection for antibiotic tolerance, which is of particular concern when pathogens are present. Members of the genus <i>Pseudomonas</i> are found in many natural microbial communities and frequently demonstrate increased abundance following triclosan exposure. The pathogen and well-studied model organism <i>Pseudomonas aeruginosa</i> exhibits high triclosan tolerance; however, it is unknown if all <i>Pseudomonas</i> species share this trait or if there are susceptible strains. We characterized the triclosan tolerance phenotypes of diverse <i>Pseudomonas</i> isolates obtained from triclosan-exposed built environments and identified both tolerant and sensitive strains. High tolerance is associated with carriage of the enoyl-acyl carrier reductase (ENR) isozyme gene <i>fabV</i>, compared to the lesser protective effects of efflux or presence of ENRs. Given its unique importance, we examined <i>fabV</i> distribution throughout <i>Pseudomonas</i> species using large-scale phylogenomic analyses. We find <i>fabV</i> presence or absence is largely invariant at the species level but demonstrates multiple gain and loss events in its evolutionary history. We further provide evidence of its presence on mobile genetic elements. Our results demonstrate the surprising variability in triclosan tolerance in <i>Pseudomonas</i> and confirm <i>fabV</i> to be a useful indicator for high triclosan tolerance in <i>Pseudomonas</i> These findings provide a framework for better monitoring of <i>Pseudomonas</i> in triclosan-exposed environments and interpreting effects on species and gene composition.<b>IMPORTANCE</b> Closely related species are typically assumed to demonstrate similar phenotypes driven by underlying conserved genotypes. When monitoring for the effect of antimicrobials on the types of species that may be selected for, this assumption may prove to be incorrect, and identification of additional genetic markers may be necessary. We isolated several phylogenetically diverse members of <i>Pseudomonas</i> from indoor environments and tested their phenotypic tolerance toward the commonly used antimicrobial triclosan. Although <i>Pseudomonas</i> isolates are broadly regarded to be highly triclosan tolerant, we demonstrate the presence of both triclosan-tolerant and -susceptible strains, separated by a difference in tolerance of nearly 3 orders of magnitude. Bioinformatic and experimental investigation demonstrated that the presence of the gene <i>fabV</i> was associated with high tolerance. We demonstrate that <i>fabV</i> is not evenly distributed in all <i>Pseudomonas</i> species and that its presence could be a useful predictor of high triclosan tolerance suitable for antimicrobial monitoring efforts involving triclosan.