CHARACTERISTICS OF ANTIBIOTIC RESISTANCE PHENOTYPES OF STAPHYLOCOCCUS AUREUS

Relevance. The issue of bacterial resistance to antibiotics has long surpassed the scope of side effects associated with antimicrobial therapy. In reality, this problem has always been far-reaching, though its full complexity, and the underlying cause-and-effect relationships, have only gradually been recognized. Today, the virtually unlimited adaptive capacity of bacteria to develop resistance to various xenobiotics, including antibiotics, is well understood. There is also growing awareness of humanity’s limited ability to foresee the global consequences of seemingly minor anthropogenic environmental influences, such as the widespread use of antibiotics. Objective. The purpose of the study was to establish the resistance phenotypes of S. aureus to β-lactam antibiotics. Materials and methods. The study included 82 strains of Staphylococcus aureus, isolated from various body biotopes of symptomatic patients and asymptomatic carriers across different age groups. The resistance phenotypes of S. aureus to β-lactam antibiotics were examined, with a comparative analysis between isolates obtained from children (n = 39) and adults (n = 43). Antibiotic susceptibility was assessed using the disc diffusion method by Bauer-Kirby on Mueller-Hinton agar, employing standard paper discs impregnated with benzylpenicillin, oxacillin, and cefoxitin. The analysis of S. aureus resistance and the identification of resistance phenotypes were performed using the WHONET 5.5 software (Copyright © 1989– 2008 World Health Organization). Results. The analysis of S. aureus resistance revealed the frequency distribution of resistance to three βlactam antibiotics. Among all 82 S. aureus isolates, the most prevalent resistance was to penicillin, observed in 89.0% of cases. Resistance to oxacillin was found in 56.1% of isolates, while resistance to cefoxitin was identified in 6.1% of the strains. Conclusion. Phenotypic analysis of S. aureus antibiotic resistance based on our data demonstrated a high prevalence of the BORSA (Borderline Oxacillin-Resistant S. aureus) phenotype, identified in 52.5% of the 82 isolates. This finding is concerning due to the increased likelihood of these strains developing multidrug resistance. In the pediatric group, the frequency of the penicillinase-producing phenotype was 1.2 times higher than in the adult group, suggesting potential overuse or inappropriate prescribing of β-lactam antibiotics in children, contributing to the selection of resistant strains. In contrast, the frequency of the mecApositive phenotype (indicative of methicillin resistance) among adult isolates was 3.6 times higher than in the pediatric group, reflecting a trend toward the accumulation of multidrug-resistant S. aureus strains with age.