Phenotypic and molecular investigation of antibiotic resistance and tolerance to biocides and heavy metals in gram-negative bacilli isolated in a university hospital

Abstract

Bacteria have been exposed to biocides and heavy metals for decades, either by the consequences of industrialization, such as the disposal of pollutants in water or soil, or even by effluent from hospitals. The current scenario in which multiresistant bacteria are widely disseminated worldwide in health care settings, such as hospitals, is alarming and of extreme concern to public health. Tolerance to biocides and heavy metals has been gaining ground in hospital pathogens, and may be contributing to the silent co-selection of antibiotics and the evolution of hospital bacteria. Antibiotic resistance is a widely studied subject, however, studies correlating resistance to antibiotics to tolerance to other antimicrobials such as biocides and heavy metals are scarce and have even been neglected. Klebsiella pneumoniae, Enterobacter spp., Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa have been the main gram-negative bacilli isolated in health care-related infections (IRAS) and, according to the World Health Organization (WHO), are pathogenic critical to bacterial resistance to antibiotics. Thus, the objective of this research project is to know the epidemiological distribution and correlation between resistance genes to antibiotics, biocides and heavy metals as well as to evaluate the tolerance phenotype to biocides and heavy metals in gram-negative bacilli isolated from blood culture from universitary hospital. For this purpose, the phenotypic and molecular investigation of tolerance to the biocides of chlorhexidine digluconate, benzalkonium chloride, triclosan and sodium hypochlorite and heavy metals silver and copper will be carried out as well as the investigation of resistance genes to broad-spectrum beta-lactam antibiotics, quinolones and aminoglycosides. Approximately 150 non-fermenting enterobacteria and gram-negative bacilli resistant to and susceptible to the abovementioned antibiotics will be studied. The chromosomal or plasmid location of genes of interest and the genomic similarity of the involved isolates will also be determined. With the data obtained in this study we intend to know and understand better the epidemiology of the tolerance to heavy metals and biocides, and the selective pressure that antibiotics, biocides and heavy metals can exert on the studied species, and thus it is possible to contribute to IRAS control measures. (AU)