RESUMEN
Hospital infections associated with multidrug-resistant (MDR) Pseudomonas aeruginosa are a worldwide public health problem. Efflux systems and biofilm formation are mechanisms related to resistance to carbapenemics. In this study, quantum dots (QDs) were used to evaluate the effect of carbonyl cyanide-3-chlorophenylhydrazone (CCCP), an efflux pump system inhibitor, on biofilm formation and antimicrobial resistance profile of P. aeruginosa strains. For this, QDs were covalently conjugated to meropenem (MPM) and incubated with a P. aeruginosa resistant isolate (P118) or a control sensitive strain (ATCC Pa27853). P118 was also analyzed with conjugates after previous CCCP efflux inhibitor incubation. Fluorescence microscopy images showed that both sensitive and resistant bacteria were efficiently labeled. Nevertheless, P118 isolates presented fluorescent cell agglomerates, suggesting biofilm formation. The addition of the CCCP changed the labeling profile of the resistant isolate, and the absence of agglomerates was observed, indicating no biofilm formation. Genetic assays revealed the presence of MexA and MexE genes encoding channel proteins from efflux pump systems in both resistant and sensitive strains. Disk-diffusion and broth microdilution tests determined drug susceptibility profiles in the presence and absence of CCCP for P118 isolates. We verified that the CCCP efflux system inhibitor may contribute to P. aeruginosa resistant phenotype reduction for some antimicrobials. This study verified the efficiency of QD-MPM conjugates to trigger and study biofilm formation, or its inhibition, before and after CCCP addition. QDs conjugated to antimicrobials can be used as nanotools to investigate multidrug-resistant bacterial strains on biofilm formation.