ANTIMICROBIAL RESISTANCE OF OPPORTUNISTIC ORAL ISOLATES: A COMPARATIVE MONITORING STUDY (2021 AND 2025)

Abstract

Introduction. The rational use of antibiotics in dentistry is a key factor that improves the quality of medical care. Monitoring studies of bacterial sensitivity to antibiotics in a time retrospective, the development of local antibiotic therapy protocols, the use of personalized approaches to the use of antibiotics are effective mechanisms for containing antibiotic resistance and achieving a rapid and effective therapeutic effect. Standardization of the interpretation of results ensures effective treatment of oral diseases of microbial etiology.

The aim of this study was to conduct a comparative study of the sensitivity of opportunistic representatives of the oral microbiota isolated from patients with periodontitis to antibiotics in a 5-year retrospective (compare isolates isolated in 2021 and 2025).

Materials and methods. The studies were conducted during 2021-2025 at the clinical and clinical-laboratory bases of the departments of the Faculty of Dentistry of the State Higher Educational Institution "Uzhgorod National University". In order to assess the antibiotic resistance of bacteria in a time retrospective manner, we conducted a comparative study of the sensitivity of bacteria belonging to opportunistic microorganisms.

In 2021, 452 bacterial isolates were isolated from 252 patients with periodontitis. In 2025, 249 patients with periodontitis were examined and 430 isolates of microorganisms were isolated, which were subjected to antibiotic sensitivity testing. The stage of periodontitis was determined according to the new classification of periodontal diseases and peri-implant conditions (2017). The study selected biological material from patients of both sexes aged 35-65 years with stage II-III periodontitis (II - moderate, III - severe with potential tooth loss).

The material for the study was taken from periodontal pockets by inserting a sterile aluminum pin with a sterile cotton swab into them. Then the pin was placed in a sterile Amies transport medium (Italy) and delivered to the laboratory. The material was sown on nutrient media by the Gold sector culture method on Himedia differential diagnostic media: blood agar (MPA + 5% blood) for the isolation of bacteria of the genus Streptococcus; Endo Agar - bacteria of the Enterobacteriaceae family, Mannitolsalt Agar - bacteria of the genus Staphylococcus, Biel esculent Agar - bacteria of the genus Enterococcus. Bacteria were identified by morphological, tinctorial and biochemical signs using systems for identification of the company Sani-Med (Ukraine). For the cultivation of anaerobic representatives of the microbiota, the nutrient medium Schedler agar + 5% sheep blood («Himedia», India) was used. To create anaerobic conditions, an anaerostat with a system for creating anaerobic conditions (AnaeroGen System – «Oxoid», Great Britain) was used. Identification of isolated pure anaerobic bacterial cultures was carried out using MALDI-TOF (matrix-activated laser desorption/ionization and time-of-flight mass spectrometry).

Antibiotic susceptibility was determined by the disk diffusion method according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST). When studying the sensitivity of microorganisms, standard disks with antibiotics manufactured by "Pharmaktiv" (Ukraine) were used.

Results. Comparative analysis of antibiotic sensitivity of bacteria of the genera Porphyromonas, Staphylococcus, Streptococcus, Enterobacteralis, Enterococccus showed that the change in the sensitivity of microorganisms to antibiotics is clearly demonstrated in the decrease in the activity of amoxicillin/clavulanate, imipenem and meropenem. A significant decrease in sensitivity to cephalosporins was noted. At the same time, it should be noted that the sensitivity to cefuroxime did not change significantly. Susceptibility to macrolides was low. The revealed variability in antibiotic susceptibility in time retrospectively (the general trend of change in antibiotic susceptibility) indicates the feasibility of a patient-oriented approach and conducting an antibiotic regimen in each individual case.

Conclusions: The analysis of changes in the sensitivity of bacterial isolates in 2021 and 2025 showed significant changes in the spectrum of effectiveness of various antibacterial drugs. The data obtained indicate a decrease in the sensitivity of pathogens to a number of widely used antibiotics, which reduces the effectiveness of empirical therapy and emphasizes the need for an individualized approach.

It was found that both anaerobic, aerobic and facultative anaerobic representatives of the oral microbiota show a general tendency to decrease in sensitivity to combined beta-lactam antibiotics, carbapenems and macrolides. A significant decrease in the sensitivity of bacteria of the genus Porphyromons to metronidazole was found. Only a tendency for the formation of resistance of the isolated isolates to fluoroquinolones was detected.

No significant decrease in the proportion of fluoroquinolone fourth-generation–susceptible strains was detected. In view of the obtained results, a patient-centered approach involving antimicrobial susceptibility testing prior to treatment initiation should become standard practice. This strategy would optimize antimicrobial selection, reduce the risk of resistance development, and improve the effectiveness of infectious disease management.

The findings also indicate the necessity of developing antimicrobial prescribing guidelines based on annual surveillance of microbial susceptibility patterns, particularly for urgent clinical situations or when susceptibility testing cannot be performed.