Assessment of Bacterial Contamination and Antimicrobial Resistance of Escherichia coli Isolates from Slovak Dairy Farms

The conditions in livestock housing are suitable for the survival of airborne microorganisms, mainly due to high temperatures, humidity, and the presence of organic material. The total count of airborne bacteria concentrations in cattle farms ranged from 3.01 log₁₀ CFU/mL to 6.90 log₁₀ CFU/mL; for coliform bacteria, they were from 2.18 log₁₀ CFU/mL to 3.34 log₁₀ CFU/mL; and for molds, they ranged from 3.00 log₁₀ CFU/mL to 4.57 log₁₀ CFU/mL. Bacteria resistant to antimicrobial substances and resistance genes can be spread on animal farms. Antimicrobial resistance in ubiquitous <i>Escherichia coli</i> isolated from cattle feces was investigated. Minimum inhibitory concentration (MIC) testing was utilized to identify phenotypic resistance profiles, and the PCR method was employed to detect the presence of resistant genes. A higher percentage of resistance was found to amikacin (65%), tetracycline (61%), streptomycin (56%), ampicillin (55%), and nalidixic acid (45%). Multidrug resistance was determined in up to 64.3% of the isolates studied. The most widespread resistance genes were <i>bla</i>_TEM (85.7%), <i>sul</i>2 (66.7%), <i>tet</i>B (52.38%), and <i>sul</i>1 (47.6%). We found that 4.8% of the <i>E. coli</i> isolates had the <i>bla</i>_CMY gene. We found that, despite phenotypic resistance, <i>E. coli</i> isolates do not necessarily carry genes conferring resistance to that particular antimicrobial agent.