Susceptibility of microflora to antibacterial drugs at different stages of hard rennet cheese production

The research aimed to analyze the susceptibility of milk microflora isolated at different stages of hard rennet cheese production and its evaluation. The susceptibility to antibacterial drugs of isolated cultures of bacteria Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii, which were found in the finished product, was determined. For each study, 15 samples of bacterial cultures were selected, and the experiment was conducted in triplicate. A total of 180 bacterial culture samples were examined. The disk diffusion method was used to determine the susceptibility of bacteria to antibacterial drugs. Studies of the resistance of bacteria isolated at different stages of hard rennet cheese “Ukrainian” production showed that the final product contains Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii resistant to certain antibacterial drugs, which may pose a health threat to consumers. Among the microflora isolated from raw milk, Escherichia coli was resistant to fluoroquinolones, penicillins, cephalosporins, tetracyclines, aminoglycosides, trimethoprim, and fosfomycin. In the normalized mixture, Escherichia coli was resistant to gentamicin and amikacin and moderately resistant to doxycycline. After pasteurization, Escherichia coli was susceptible to ciprofloxacin and resistant to all other tested antibacterial drugs. Resistance to gentamicin and amikacin, as well as moderate resistance to doxycycline, was maintained at almost every stage of production and in the final product. After pasteurization, these bacteria isolated from the brine became resistant to most antibacterial drugs, except for ciprofloxacin, gentamicin, amikacin, and fosfomycin. Klebsiella pneumoniae, isolated from the brine, was resistant to ampicillin after its pasteurization. It was resistant to fosfomycin both before and after pasteurisation of the brine. The bacterium isolated from the finished cheese retained resistance to fosfomycin and ampicillin. Acinetobacter baumannii, isolated from both the raw milk and the final product, was resistant to cefotaxime. Moderate susceptibility to amikacin and fosfomycin was restored after cheese maturation.