Virulence properties and antimicrobial resistance of Pseudomonas aeruginosa isolated from cave waters at Roraima Tepui, Guayana Highlands.

Pseudomonas aeruginosa is a prominent member of emerging waterborne pathogens. The environmental reservoirs of multi-resistant phenotypes and other virulence factors in this bacterium are poorly understood. Our study aimed to determine the virulence properties of P. aeruginosa isolated from Roraima Sur Cave (RSC) waters at Guayana Highlands. Based on the best identification at species level by biochemical tests, 16S rRNA sequencing and phylogenetic inferences, one RSC isolate named LG11 was characterized for virulence properties in comparison with P. aeruginosa reference strains. PCR amplification of alginate, elastase, exoenzyme S, exotoxin A, neuraminidase and Quorum-Sensing genes showed a high virulence potential in LG11. This isolate demonstrated multi-resistance to ceftriaxone, tigecycline and imipenem. Pyocyanin production was greater in LG11 (0·478 µg ml ) than the strain ATCC 10145 (0·316 µg ml ), but the highest pigment concentration (2·140 µg ml ) was displayed by the clinical strain CVCM 937 (P = 0·000175). Pronounced biomass production on granite and glass (P < 0·05) and well-developed biofilms indicated the ability of P. aeruginosa from RSC to colonize surfaces found in human and healthcare environments. These data suggest that waters from pristine ecosystems such as RSC could be reservoirs of this opportunistic bacterium carrying important virulence properties with potential epidemiological implications. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows for the first time the occurrence of virulence genes and multi-resistance to antimicrobials in Pseudomonas aeruginosa isolated from cave waters at Guayana Highlands. These findings, together with the biofilm formation on surfaces found in human and healthcare settings, suggest public health risks and the potential of these virulence properties to be transferred from or to native populations in waters. Our results provide important insights to the current knowledge of P. aeruginosa in the environment, setting the basis for future studies driven to assess reservoirs of multi-resistant bacteria and virulence features unknown in pristine ecosystems.