Background. A microbial nature of periodontitis requires an accurate analysis of the pathogenic potential of the periodontal pocket microflora thereby enabling correct diagnosis to be made and the most effective pharmacological agent to be selected for treating chronic periodontitis. Metronidazole demonstrates excellent results for anaerobic microorganisms in the periodontal pocket, whereas minocycline hydrochloride, moxifloxacin and amoxicillin/clavulanate are efficient for aerobic microorganisms. However, specialists find considerably relevant to analyze the correlations between specific bacterial associations in the periodontal pocket against local antibacterial therapy, as well as to track the contents of periodontal pockets long after antibacterial therapy. Therefore, a microbiological analysis of periodontal pocket contents is considered necessary in order to select and monitor the effectiveness of local antibacterial therapy.Objective. To evaluate the effectiveness of local antibacterial therapy for chronic generalized periodontitis by means of analysis of changes in the microbiological composition of periodontal pockets.Methods. The clinical trial involved 144 patients with chronic generalized periodontitis. The study included examination of patients and analysis of clinical data bases of the Department for General Practice Dentistry, Kuban State Medical University and the Dentistry Department, Stavropol State Medical University of the Ministry of Health of the Russian Federation. The trial included patients aged 30 to 60 with a diagnosis of chronic generalized periodontitis of different severity. All periodontitis patients were divided into 2 groups depending on the therapy: main and control groups. Each group had three subgroups depending on the severity of the pathologic process. The first subgroup of the control group (chronic generalized periodontitis of mild degree) consisted of 16 people (11.1%), the second subgroup (chronic generalized periodontitis of moderate degree) — 31 people (21.5%), the third subgroup (chronic generalized periodontitis of severe degree) — 7 people (4.9%). The first, second and third subgroups of the main group consisted of 28 (19.4%), 48 (33.3%) and 14 persons (9.7%) respectively. The severity of periodontitis was determined by the depth of the periodontal pocket, degree of bone resorption (according to x-ray examination), and pathologic tooth mobility. A local anti-inflammatory therapy for the patients of the control group included oral baths with propolis (15–20 drops of 10% propolis tincture diluted in 100 ml of warm water) 3 times a day for 7 days starting from the first visit. At the final stage of treatment after preliminary scaling and rootplaning, patients of the control group received antiseptic gel with 10% metronidazole and 2% chlorhexidine bigluconate to be injected into periodontal pockets with over 4 mm depth. Additionally, applications of adhesive dental films Diplene Denta L (with lincomycin) and Diplene Denta M (with metronidazole) were prescribed to be done in the home. In addition to the above-mentioned comprehensive therapy, patients of the main group received a single insufflation of minocycline hydrochloride microspheres into each periodontal pocket. The tools for the patients of the main group included plastic cannulas with minocycline hydrochloride microspheres in the form of powder in the tip of the cartridge, and a special syringe-insufflator. The technique of antibiotic insufflation into the periodontal pocket was preliminary trained on the model of jaws with the studied pathology. Statistical analysis of the results was performed using variance analysis in the Excel Microsoft Office 2016 (Microsoft, USA).Results. According to the systematic observation of the patients from the control group, periodic fluctuations in microbial population in the majority of pathologic pockets obtained a specific regularity: a decrease in the number of microorganisms on day 21 was followed by its increase in the subsequent period of observation after 30 and especially 60 days. According to the ongoing follow-up of the patients of the main group, fluctuations of microbial population in the majority of pathologic pockets obtained a certain regularity: a significant reduction in the number of microorganisms on day 21 was followed by its slight rise in the subsequent period of observation after 30 and a slight increase again in 60 days. Fluctuations in the number of microorganisms of periodontal pockets in the main group reveal their specific character: their number remained invariably lower than that of the control group throughout the observation period, while the total number of detected periodontopathogens decreased.Conclusion. The established correlations between the main indicators of microbiological status of periodontal pockets and the severity of chronic generalized periodontitis within different periods after the local therapy confirm the positive dynamics of treatment in the main group, where patients were insufflated with minocycline hydrochloride microspheres, proved by a change in the typology of microbial status of periodontal pockets and a number of periodontopathogenic microorganisms.