Bactericidal activity and sanitary–microbiological effectiveness of the biocidal preparation “Crezonid”

Under modern conditions of veterinary medicine and industrial livestock production, effective disinfection has acquired strategic importance as a key component of biosecurity systems, prevention of infectious diseases, and containment of antimicrobial resistance within the One Health concept. High microbial load, significant organic contamination (blood, feces, feed residues), and the ability of pathogens to form biofilms substantially reduce the effectiveness of many traditional disinfectants. Therefore, the development and comprehensive evaluation of new biocidal preparations combining high antimicrobial activity, stability in the presence of protein impurities, and an acceptable safety profile are highly relevant. The aim of the study was to experimentally investigate the bactericidal activity of the biocidal preparation “Crezonid” and to determine its sanitary–microbiological effectiveness against opportunistic microorganisms. The study was conducted using the suspension method in accordance with DIN EN 1656:2010-03, DSTU EN 1040:2004, and EN 12353 standards, employing test cultures of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 6538 at a concentration of 2 × 10⁹ CFU/cm³. It was established that “Crezonid” exhibits pronounced bactericidal action: the minimum effective concentration is 0.5 % with an exposure time of 30 minutes, ensuring complete inhibition of both test microorganisms. At a concentration of 1.0 %, the bactericidal effect was observed after 10 minutes of exposure. The bactericidal dilutions were 1:240 for E. coli and 1:320 for S. aureus (10-minute exposure without protein load). The phenol coefficient, calculated relative to reference phenol, reached 2.8 for E. coli and 3.4 for S. aureus, indicating a 2.8–3.4-fold higher bactericidal activity compared to phenol. Special attention was paid to the preparation’s resistance to organic contamination. The protein index, defined as the ratio of bactericidal dilutions without protein to those in the presence of inactivated bovine blood serum, was 2.95 (calculated 2.9–3.0) for E. coli and 3.15 (3.1–3.2) for S. aureus without load; in the presence of protein, it was 1.3 and 1.4, respectively. Such low index values (1.3–1.4) indicate minimal reduction in effectiveness under conditions typical of livestock facilities, representing a significant advantage compared to phenol (index 2.0–2.2) and some quaternary ammonium compound–based agents (1.6–1.8). Comparative analysis with analogues (“Chas Pik”, “Biokontakt,” phenol) confirmed that “Crezonid” exceeds or is not inferior to competitors in terms of phenol coefficient and bactericidal dilution, while demonstrating superior resistance to protein load. This allows the preparation to be recommended for use at lower working concentrations, contributing to economic efficiency and reducing toxic load on personnel and the environment. The obtained data substantiate the feasibility of using the biocidal preparation “Crezonid” for preventive and emergency disinfection of surfaces, equipment, and vehicles in veterinary practice, livestock complexes, and veterinary–sanitary control facilities. Prospects for further research are associated with studying the agent’s effectiveness under real production conditions, evaluating its activity against biofilms, and assessing its spectrum of action against a wider range of pathogens, including mycobacteria and spore-forming microorganisms.