Pesquisa de Staphylococcus aureus enterotoxigênicos formadores de biofilmes isolados de bovinos com mastite em rebanhos leiteiros e perfil de resistência frente a desinfetantes

Abstract

Dairy production in Brazil stands out as one of the most important activities for Brazilian livestock, being responsible for the source of income of millions of Brazilians. However, this activity is constantly influenced by the occurrence of mastitis, especially in the subclinical form, which occurs in herds. Staphylococcus spp is the main genus of mastitis-causing bacteria in cattle. The aim of this study was to investigate enterotoxigenic Staphylococcus aureus biofilm-forming isolates from bovine mastitis in dairy herds and to profile resistance against disinfectants. Ten farms linked to a federally registered Milk Processing power plant were selected. Physical examination of the mammary gland and milk of the animals was performed and then the California Mastitis Test. Samples were collected from 960 animals for microbiological examination after antisepsis of the roof ostium with 70 ° GL alcohol. In the laboratory, aliquots of 10 μl of milk were seeded on 5% sheep blood agar and then plates incubated at 37 ° C for 48 hours. Subsequently, 213 isolates Staphylococcus spp. classified as strong and moderate biofilm producers were selected for characterization regarding the phenotypic profile and presence of the femA gene for identification of S. aureus. Of these, 152 isolates were confirmed, which were subjected to detection of genes capable of producing biofilms (icaA, icaD and Bap), genes encoding enterotoxins (SeA, SeB, SeC, SeD, SeE), and resistance related genes (Tet (k), Vana). The action of disinfectants (chlorhexidine and lactic acid) used in the milking routine on biofilm in formation and consolidated in 86 of these samples was tested. In 84.16% (134/152) of the samples the BAP gene was found, in 78.29% (119/152) the IcaD gene and in only 1.32% (2/152) the IcaA gene. Only enterotoxins Sec in 17.76% (27/152) of the samples and See in 0.66% (1/152). TetK resistance genes were found in 48.68% (74/152) of the samples. Satisfactory results were observed for the two disinfectants tested on the biofilm in formation, in 94.2% (81/86) of chlorhexidine isolates and 100% of lactic acid isolates. However, for the consolidated biofilm the action percentage was much lower, the lactic acid showed low efficacy over the already formed biofilm, with only 3.5% of reduction rate, while chlorhexidine was able to reduce 43% of the consolidated biofilm. The effect of disinfectants on reducing biofilm adhesion was quite significant. Research into more effective products that act on both free bacterial cells and microorganisms in the form of biofilms is suggested.