Identificação molecular de bactérias psicrotróficas, detecção de genes de virulência e perfil de resistência a antimicrobianos

Abstract

The cooling of the milk in the producing property is an important method of preserving the raw material, but may favor the development of psychotrophic deteriorating and opportunistic pathogenic bacteria, such as Listeria monocytogenes. The objective of this study was to evaluate the milk produced in agreste region of Pernambuco regarding the concentration of psychrotrophic bacteria and their enzymatic characteristics, identifying those with deteriorating potential, as well as to verify the occurrence of Listeria spp. potentially pathogenic, qualifying them for antimicrobial resistance profile. The mean concentration of psychrotrophic bacteria was 2.1 x 105 CFU/mL of refrigerated raw milk. However, in 58.3% of the farms psychrotrophic counts were below 10 CFU/mL. Lipolytic and/or proteolytic activity was demonstrated by 38% of the psychrotrophic isolates, which were identified in 13 species. Aeromonas, Exiguobacterium and Staphylococcus were dominant genera, covering 77% of the isolates and, to a lesser extent, Macrococcus, Bacillus, Paenibacillus, Enterobacter, Hafnia, Enterococcus and Lactococcus. Regarding ocourrence of Listeria spp., 140 presumptive isolates were obtained, of which 32.85% were confirmed for the genus Listeria. Of these, 8.69% presented the three virulence genes investigated - hlyA, inlA and actA, indicating that these isolates possess properties of a virulent strain. The antimicrobial resistance profile of Listeria spp. demonstrated that vancomycin, gentamicin and tetracycline are the most effective drugs against these bacteria. Ampicillin was the antimicrobial with the highest resistance index, presented by 60.87% of the isolates. The results of this work allow us to infer possible failures in the production and storage of raw milk and to adjust hygienic-sanitary and control procedures in order to avoid high concentration of psychrotrophic bacteria and consequent production of deteriorating enzymes. It is also inferred that milk produced and stored cold in the agreste of Pernambuco constitutes a risk to public health and to the milk production chain of the State for the presence of Listeria spp. potentially pathogenic and multi-resistant to antimicrobials.