Relationship between antibiotic resistance and biofilm production of Staphylococcus aureus isolates from bovine mastitis

The objective was to analyze the relationship between the antibiotic-resistance profile and the biofilm formation of S. aureus isolates from bovine mastitis. Thirty (30) isolates of S. Rev Mex Cienc Pecu 2021;12(4):1117-1132 1118 aureus from cases of subclinical mastitis in dairy farms in semi-intensive production and backyard production systems, located in the states of Guanajuato and Michoacán, Mexico, were analyzed. An antibiogram was performed by the Kirbi-Bauer disc-diffusion method. Biofilm formation was determined by the violet crystal staining method. For the evaluation of antibiotic resistance genes and biofilm formation, genomic DNA was obtained from a colony for the identification of the genes: blaZ, mecA, tetK, tetM, gyrA and gyrB, and icaA and icaD. The results showed that 100 % of the isolates were resistant to penicillin and dicloxacillin, followed by cefotaxime (86.6 %), ampicillin and cephalotin (83.3 %) and ceftazidime (80.0 %), while a 36.6 % resistance to oxacillin was observed. It was identified that all isolates of S. aureus had the ability to form biofilm with a range between 20 to 98 %. It was also observed that isolates with a high multi-resistance presented a greater formation of biofilm, establishing a significant positive correlation. In conclusion, S. aureus isolates from bovine mastitis presented high levels of antibiotic resistance; as well as an important biofilm-forming capacity, demonstrating the existence of a positive correlation between these two factors.