Integrated chemical and microbiological monitoring of food safety: resistant pathogens and antibiotic residues in the northern region of Kazakhstan

Animal-derived products are an important factor in the transmission of both antimicrobial residues and resistant pathogens, which affect food quality and pose a threat to public health. Despite the importance of these hazards, no integrated studies combining microbiological and chemical analyses had been carried out in northern Kazakhstan. This study therefore aimed to detect resistant pathogens and antibiotic residues in retail cow’s milk and chicken meat and to explore possible links between the two parameters. Its novelty lies in integrating phenotypic resistance profiles with quantitative residue data obtained from the same samples, providing a deeper insight into food borne risks associated with antimicrobials. A total of 108 retail samples were collected in Kostanay region (Kazakhstan) (70 milk and 38 chicken meat). Standardised GOST/ISO protocols were used to isolate and identify Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, Klebsiella pneumoniae and Listeria monocytogenes. Phenotypic resistance to 17 antibiotics was assessed by the disk diffusion method (EUCAST/CLSI). Residues from 6 drug groups (tetracyclines, β lactams, aminoglycosides, bacitracin, chloramphenicol and nitrofuran metabolites) were quantified by solid phase ELISA (RIDASCREEN® and EuroProxima kits). 37 pathogenic isolates (34.3 %) were recovered: 13 E. coli, 12 S. aureus, 8 Str. agalactiae, 3 K. pneumoniae and 1 L. monocytogenes. Multiple drug resistance was frequent: 46 % of E. coli were resistant to ampicillin, amoxicillin and tetracycline, and 38 % to fluoroquinolones; one third of S. aureus were resistant to benzylpenicillin and tetracycline; 75 % of Str. agalactiae were resistant to vancomycin and tetracycline. L. monocytogenes remained susceptible to all tested drugs. ELISA detected antibiotic residues in every sample. Chloramphenicol and nitrofuran metabolites—both prohibited in food animals—were found in 100 % of samples, albeit below method detection limits. Penicillin residues in some meat samples approached the maximum permitted level (50 µg/kg; mean = 7.5 ± 3.9 µg/kg), whereas other drug concentrations complied with EU/EEC limits. It should be noted that the maximum residue limits (MRL) for individual veterinary drugs vary in some cases in the regulatory systems of the ECC and the EU, which may affect the assessment of conformity and food safety in different regions. No direct correlation was seen between residue presence and phenotypic resistance, underscoring the complex nature of antibiotic resistance development. In conclusion, retail milk and chicken meat may simultaneously contain multiple resistant pathogens and antibiotic residues, including prohibited ones. A direct relationship between these factors has not been established, which indicates the complex nature of resistance formation. The results confirm the need for comprehensive control and rational use of antibiotics in animal husbandry. The results of the study can be used to improve sanitary control of food products and prevent the spread of antibiotic-resistant microorganisms.