Antibiotic resistance of microorganisms isolated from cows with subclinical mastitis

Abstract

Cow mastitis is a polyetiological disease involving pathogenic microorganisms. Antibiotics are used to treat sick animals, which contributes to the development of resistant clones of bacteria, and consumption of the corresponding milk leads to the spread of antibiotic-resistant microorganisms. The purpose of the work is to determine strains of antibiotic-resistant bacteria in the milk of cows suffering from subclinical mastitis. Bacteriological studies of mammary gland secretion samples were performed by inoculating the sediment obtained after centrifugation of the examined material on an agarised nutrient medium (with 5% ram erythrocytes). The study of antimicrobial sensitivity was performed by the disk diffusion method. It was established that pathogens with multiple resistance to antibiotics circulate among cows suffering from mastitis on the farm, which indicates their indiscriminate use in animal therapy schemes, in particular mastitis. It was found that the overall level of phenotypic resistance to antimicrobial agents of the examined isolates was within 19-33% (in Staphylococcus spp. – 19.9%, in E. coli – 33.2%, in Enterococcus spp. – 32.5%). The analysis of the results allowed assigning the culture study to the category of multiresistant: 31.6% of cultures of Staphylococcus spp. demonstrated resistance to five groups of antibiotics; 54.5% of Escherichia cultures – up to five groups of antibiotics; 37.5% of cultures of Enterococcus spp. resistant to three groups of antibiotics. It was established that 100% of the studied cultures of Staphylococcus spp. are sensitive to netilmicin, sparfloxacin, gatifloxacin and clarithromycin. Therewith, 100% of the examined cultures of Enterococcus spp. sensitive to gentamicin, norfloxacin, and nitrofurantoin, and 100% of the examined E. coli cultures were sensitive to cephalothin, meropenem, gentamicin, tobramycin, amikacin, nitroxoline, and gatifloxacin. Thus, dairy cows suffering from subclinical mastitis are a source of bacteria with multiple resistance to antibiotics and carry risks for consumers due to the consumption of dairy products contaminated with pathogens of zoonotic diseases, which requires proper control by veterinary service specialists