Effluents from a university clinical analysis teaching laboratory: an inductive study on adhesion and cellular response of Pseudomonas aeruginosa

Abstract

Microbial resistance to antibiotics is a global threat and the World Health Organization (WHO) predicts that future pandemics will involve resistant microorganisms. Recently, the WHO published a list of pathogenic microbes whose priority level varies among medium, high and critical. All bacteria in the list can form biofilms. Biofilms are structures made of polymeric adhesive matrix composed by multispecies in close association. Additionally, biofilm provides an important physical barrier. Different phenotypes are found in biofilms, ensuring resistance to oxidative stress, as well as environmental stress factors. It results cell persistence because there is generation of a gradient of chemical inhibitors at subinhibitory levels, which promote the development of resistant subpopulations able to grow and disseminate. Clinical analysis laboratories are sources of selective pressures for potentially pathogenic bacteria because different substances are handled and discarded daily by the effluents generated. This study assessed the activity of a highly toxic leachate on isolates of Pseudomonas aeruginosa recovered from the sinks of a university clinical analysis teaching laboratory. In vitro biofilm formation tests, pyocyanin quantification, cell wall hydrophobicity test, motility test and susceptibility to seven antibiotics were carried out. The isolate with the most antibiotic resistance was assessed. There was a reduction in adhesion of 14 to 430%. Biofilm was formed, however, on all tested materials; the cells preferentially adhered to hydrophilic surfaces, dolomite, followed by galvanized iron and glass. Maximum pyocyanin production was 12 mM. Swimming motility was stimulated, recording a 12-fold increase in speed, while swarming and twitching motility were inhibited by around 20 and 60%, respectively. All isolates were resistant to cephalosporins and one isolate was detected resistant also to ciprofloxacin. The results indicated that P. aeruginosa survived the leachate, triggering different adaptive physiological responses to persist in the stressful environment.