Avaliação fenotípica e genotípica da resistência a fármacos antimicrobianos de bastonetes Gram- negativos não fermentadores isolados de espécimes clínicos hospitalares

Abstract

The introduction of antimicrobials in the 1930s revolutionized medical practice and promoted advances in therapeutic approach to patients with infectious diseases. Originally, it was thought that they would be an absolutely effective solution, providing the cure for these patients, controlling diseases that, until then, had decimated populations. However, it was soon realized that the use of these drugs could promoted an unwanted effect, namely the selection of samples resistant to them, an increasingly worrying conundrum. Among the sites that most favor the spread of antimicrobial resistance, the environments related to health care deserve mention. Among the microorganisms of current clinical relevance, the non-fermenting Gram-negative rods stand out, including Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia, respectively. This study aims at the phenotypic and genotypic evaluation of antimicrobial resistance in samples of A. baumannii, P. aeruginosa and S. maltophilia sampled from hospitalized patients. The phenotypic and genotypic resistance profiles were evaluated by disk diffusion and polymerase chain reaction. The results obtained for the samples of A. baumannii revealed high percentages of resistance to antimicrobials. β-lactams resistance, the most commonly used drugs, stood out as higher than 80%. Genes that encode resistance to this group of antimicrobials, such as blaOXA-23, blaKPC, blaVIM and blaOXA-143, were also frequently detected. P. aeruginosa showed lower percentages of phenotypic resistance, ranging between 10 and 34%, but that still arouse concern. In samples of these species, the genetic markers aac (6’)-Ib-cr, blaBEL-1, blaCTX-M, blaGES, blaKPC-2, blaSHV and blaVIM were observed. Contrastingly, S. maltophilia presented a sample resistant to the two tested antimicrobials and no resistance marker, in contrast to the other three samples of the microorganism which, although were shown to be sensitive in the antibiogram, harbored genetic markers related to resistance to antimicrobials. The study of bacterialresistance to antimicrobial drugs and mechanisms related to the expression of the trait are an important tool to support the design of strategies aimed at controlling the evolution of resistance rates, minimizing the repercussions of this property.