Caracterização fenotípica e molecular de bactérias multirresistentes isoladas em um hospital universitário

Abstract

Healthcare-associated infections are a global concern, as they often involve multidrug resistant and virulent microorganisms, increasing mortality, hospital costs, and patient insecurity. These bacteria, both Gram-negative and Gram-positive, spread easily and can become superbugs by acquiring virulence factors and developing resistance mechanisms such as extended-spectrum β-lactamase (ESBL) production, carbapenemases, and vancomycin resistance. Thus, the present study investigated the antimicrobial resistance profile and virulence factors in multidrug-resistant bacteria isolated by the University Hospital of Lagarto (HUL), through phenotypic and genetic characterization. The project was approved by the Teaching and Research Management of HUL and by the Ethics Committee of the Federal University of Sergipe. The research was conducted between September 2023 and January 2025. Fifty strains were analyzed, and tests were performed for the detection of antimicrobial resistance, phenotypic detection of ESBL through the double-disk synergy test, and phenotypic detection of carbapenemases through the modified carbapenem inactivation method. Molecular tests were carried out to verify the presence of genes encoding ESBLs and carbapenemases. Tests were also conducted to detect virulence factors (polysaccharide capsule, type 1 fimbriae, hypermucoviscosity, and biofilm). Paeruginosa species were subjected to genetic testing for virulence genes (aprA, plcN, plcH, algD, and lasB). The most frequently found microorganism was Klebsiella pneumoniae (52 %), followed by Pseudomonas aeruginosa (14 %), Escherichia coli (10 %), Enterococcus faecalis (6 %), and other bacteria (18 %). The main source of isolates was urine (52 %). Regarding antimicrobial resistance, K. pneumoniae showed 92% resistance to fourth-generation cephalosporins and 73 % to carbapenems. Paeruginosa showed 100 % resistance to carbapenems, and E. coli showed 100% resistance to fluoroquinolones. Enterococcus faecalis and faecium showed 100% resistance to both vancomycin and teicoplanin. The most prevalent ESBL gene was TEM, with 51.1 %. 22.2 % of Gram-negative samples simultaneously harbored TEM + SHV + CTX-M-1 genes. The blaKPC gene was the most prevalent carbapenemase, detected in 40% of isolates, especially in P. aeruginosa (85.7 %). 35.1 % of Gram negative samples presented both carbapenemase and ESBL genes simultaneously. The vanA gene was found in 60 % of Enterococcus isolates. Among the virulence factors, 78 % had a polysaccharide capsule, 66 % had type 1 fimbriae, 94 % were biofilm producers, and all P. aeruginosa strains presented the tested virulence genes. The results confirmed the national trend of increasing detection of multidrug-resistant Gram-negative bacteria, especially K. pneumoniae and P. aeruginosa. The significant detection of biofilm and other virulence factors indicates a high infectious potential of the strains. The findings will serve as a basis for future studies and may contribute to improving the institution's protocols in combating healthcare-associated infections.