Avaliação de fatores de virulência de cepas nosocomiais de Acinetobacter baumannii

Abstract

Acinetobacter baumannii is a Gram-negative coccobacillus, opportunistic, and emerging as a nosocomial pathogen. Its success as an infectious agent is attributed to several virulence factors, particularly its ability to form biofilms, release extracellular proteases, and develop resistance to antimicrobials. This study aimed to investigate the secretion of proteases by different strains of A. baumannii, biofilm formation, and antibiotic resistance profiles, seeking to understand the influence of these factors on the pathogenicity of this bacterium. Twenty strains from the University Hospital of Ponta Grossa were analyzed and confirmed as A. baumannii through glucose and lactose oxidation tests and growth at 42°C. Qualitative tests of proteolytic degradation revealed that, of the 20 strains analyzed, 7 (35%) showed a degradation halo for both skim milk and milk agar media, while 13 (65%) exhibited this characteristic in only one of the media. The results of the qualitative caseinolysis tests in liquid medium partially confirmed these findings, as only 20% of the samples showed minimal casein degradation. Similarly, zymography revealed the presence of enzymatic activity bands around 25 kDa and 10 kDa. The samples ABHU1 and ABHU4 showed proteolytic activity in all applied tests. Furthermore, they demonstrated satisfactory results for the biofilm formation test, being classified as strong biofilm producers. All samples were resistant to the tested antimicrobials, except for colistin. Despite the large number of studies involving the association between A. baumannii with hospital outbreaks, severe infections, and antimicrobial resistance, factors that determine the virulence and pathogenicity of this microorganism need to be studied in depth. It becomes evident that the ability to form biofilms, in addition to other characteristics of this microorganism, can be considered an important virulence factor common to a large number of A. baumannii isolates. Detailed investigations still need to be conducted to provide new data on the proteases released by different strains of A. baumannii and their role in pathogenesis.