Assessment of the content of Gram-positive strains of microorganisms identified in the production environment of livestock complexes

Introduction. Modern livestock enterprises ensure the country's food security. The implemented automation of technological processes can reduce the impact of traditional harmful factors. In this regard, it is the biological factor that is one of the main occupational risk factors. The widespread use of antibiotics and feed additives contributes to the emergence of multidrug‑resistant strains. Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) are circulating among animals and the environment and can pose a danger to people in contact with animals.

The study aims to evaluate the content and resistance to antibacterial drugs (with the identification of resistance genes) of priority gram-positive microorganisms that cause opportunistic infections in the production environment of the livestock complex.

Materials and methods. The authors analyzed the content of gram-positive strains of microorganisms detected in the production environment of livestock complexes and studied the antibiotic sensitivity of isolated strains of Staphylococcus aureus and Enterococcus faecalis. The scientists conducted the diagnosis of methicillin resistance in 89 isolates of Staphylococcus aureus by PCR with hybridization-fluorescence detection.

Results. The content of microorganisms in the air of the working area ranges from 112,124 to 242,700 thousand microbial bodies/m³. Gram-positive flora dominates, with representatives of the genus Enterococcus predominating (in 60±5.3% of samples). The total content of bacteria of the genus Staphylococcus is up to 20±4.6% of samples.

In the structure of microorganisms, when examining flushes from surfaces in the work area, the predominance of strains of the genus Staphylococcus (in 90±3.8% of samples) and the genus Enterococcus (in 95.0±0.5% of samples) was established, the species Enterococcus faecalis was isolated in 85.0±2.7% of samples.

Gram-negative flora was identified in 40±1.6% of samples (Proteus vulgaris, Echerichia coli, Citrobacter freundii, Klebsiella spp. in the amount of 10⁶ CFU/tampon). The bulk of the isolated microorganisms consisted of 2-3-component cultures (90±1.6%). The strains demonstrate resistance to: tetracyclines (100%), macrolides (88.2%), fluoroquinolones (ciprofloxacin — 35.3%, norfloxacin — 41.2%), lincosamides (clindamycin — 88.3%); aminoglycosides (amikacin — 82%, gentamicin — 58.8%, tobramycin — 88.2%), penicillins (ampicillin — 57%) and glycopeptides (vancomycin — 46.6%).

All Staphylococcus aureus is characterized by simultaneous resistance to several antibiotics. In the studied sample, Staphylococcus aureus methicillin resistance (mecA) DNA was identified in 38.2% of the analyzed samples.

All isolates of the Enterococcus faecalis species demonstrate 100% resistance to imipenem and erythromycin, and sensitivity to ampicillin in 90.1% of cases. Up to 90% of the strains are resistant to gentamicin, levofloxacin and ceftriaxone. Half (50.0±5.50%) of Enterococcus faecalis isolates have multiple drug resistance (to three or more classes of antibacterial drugs).

Limitations. The limitation of this study is the simultaneous sampling in winter, before cleaning and disinfection of premises and equipment.

Conclusion. To assess the health risks of employees of livestock enterprises, a comprehensive sampling strategy using additional sampling methods, as well as the use of a combination of various nutrient media and molecular methods for isolating resistance genes of identified microorganisms, is of paramount importance. Reduction of microbial contamination of the air should be ensured by compliance with the regulated requirements for the sanitary and hygienic maintenance of animals. Comprehensive health improvement plans should include preventive and focal disinfection, disinfection and deratization. Due to the growing need for the rational use of available antimicrobial drugs, taking into account the spectrum of their activity and the profile of antibiotic resistance of the main pathogens, the results of the research can be used in the treatment of inflammatory diseases in employees of these enterprises.

Ethics. The conducted research did not require the conclusion of the Ethics Committee.

Contributions:
Masyagutova L.M. — review of publications on the topic, analysis of literary sources, generalization of data;
Gizatullina L.G. — sampling for bacteriological analysis, conducting research, analyzing the results;
Bakirov A.B. — data synthesis, editing;
Zaidullin I.I. — material processing, editing.
All co-authors — responsibility for approving the final version of the article and ensuring the integrity of all parts of the article.

Funding. The study had no funding.

Conflict of interest. The authors declare no conflict of interest.

Received: 17.07.2025 / Accepted: 24.07.2025 / Published: 05.09.2025

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