Potencial de resistencia a los antimicrobianos de Staphylococcus aureus inductor de mastitis subclínica de bovinos lecheros y presente en secreciones nasales de los ordeñadores

Abstract

Staphylococcus aureus is one of the saprophytic bacteria commonly found on the skin and mucous membranes of animals, being one of the bacteria with the highest incidence in subclinical mastitis. At present, one of the most relevant problems is the reckless and indiscriminate application of antibiotics, leading to subclinical mastitis presenting different resistance mechanisms to various antibiotics available on the market. The objective of the following research is to evaluate the antimicrobial resistance of Staphylococcus aureus in dairy cows and milkers in the Quero canton, Yanayacu-Mochapata parish, Tungurahua province, Caserío 12 de Octubre on the Velazco family farm. Eighty milk samples were collected and tested for subclinical mastitis using the California Mastitis Test. We found 28 positive animals for subclinical mastitis, of which 12 were positive for Staphylococcus aureus. Five samples were also taken from the milkers by means of a nasal swab, resulting in all samples positive for Staphylococcus. aureus. The samples were taken to the microbiology laboratory of the Faculty of Agricultural Sciences of the Technical University of Ambato where: type of hemolysis, gram staining, biochemical tests in salt-mannitol and catalase/coagulase test were carried out. Finally, the bacteria were isolated and the respective antibiogram with the Kirby-Bauer method was performed. The prevalence of subclinical mastitis was 35% of the total samples and 42% were samples positive for Staphylococcus aureus. The results in dairy cows were: none of the samples were resistant to gentamicin, chloramphenicol and rifampicin; 8.3% were resistant to clindamycin, 25% of the strains were resistant to novobiocin and 16.6% were resistant to linezolid. In the milkers the results were 40% of the strains resistant to gentamicin, 40% resistant to rifampin, 60% of the samples resistant to clindamycin and 60% resistant to novobiocin. Keywords: subclinical mastitis, Staphylococcus aureus, biochemical tests, resistance.