Dissemination of antimicrobial resistance and Potassium Tellurite (PT) in the hospital environment: can the use of means with Tellurite and the detection of insertion sequences contribute to prevention and intervention?

Multidrug resistance is a public health problem. Enterobacteriaceae strains may be reservoirs of antimicrobial and potassium tellurite (PT) resistance genes, which is a determinant of bacterial escape to intraphagocytic killing mechanisms. The mobility of resistance genes and their genetic rearrangements are significantly involved in the dissemination of these genes. Mobile genetic elements such as integrons and transposons, as well as IS26 (considered among the predominant ISs), facilitate the formation and mobilization of sets of resistance genes in plasmids capable of transferring these determinants of resistance and virulence horizontally. There is evidence of associations, in plasmids, of genes encoding adhesins, toxins and antimicrobial resistance, possibly related to PT resistance. In the present work, 342 samples were collected for bacteriological culture in different units of a University Hospital in Rio de Janeiro, Brazil (Hospital Kitchen, Medical and Surgical Clinics Wards, and Intensive Care Unit): 98 samples from hands of professionals, 85 hand samples from food handlers, 104 stool samples (rectal swab) from patients and 55 food samples. We isolated 27 strains of Enterobacteriaceae through selective media containing cephalothin (32µg/mL). Bacterial identification was performed by conventional phenotypic methods. Antimicrobial susceptibility tests, as well as the phenotypic test for Extended-Spectrum Beta-lactamases (ESBLs) production, were performed by disk diffusion. PT resistance was also tested by direct seeding in media with 25µg/mL and 112 µg/mL of the compound. Plasmids were visualized by agarose gel electrophoresis of bacterial DNA extracts. Additionally, antimicrobial resistance genes and IS26 were detected by PCR assays. From a total of 27 strains of Enterobacteriaceae isolated, eight strains of Enterobacteriaceae were selected, considering phenotypes indicative of ESBLs production, resistance to aminoglycosides and presence of plasmids of high and low molecular weight (from the hands of food handlers, food and feces from hospitalized patients).  Three strains 3/8 (37.5%) were resistant to aminoglycosides and cephalosporins, concomitantly. Four 4/8 strains (50.0%) were positive for the phenotypic test for ESBL production and six 6/8 strains (75.0%) were resistant to PT. Strains with resistance to aminoglycosides and producing ESBL showed amplification product for the genes tested. We consider that these antimicrobial resistance genes, also the determinants for resistance to PT (as a bacterial virulence factor), as well as IS26, may contribute to the plasticity and fitness of R plasmids, in different environments, favoring the circulation of relevant pathogenic strains.