Role of Biofilms in Pathogenesis and Clinical Course of Recurrent Tonsillitis and Peritonsillar Abscess. Summary of the Doctoral Thesis
Authors:   ,   Rīga Stradiņš University, Vīksne (Klagiša) Renāta 
Published: November 2023

After nasopharyngitis and otitis media tonsillitis is the 3rd most common infection that requires patients to see an otorhinolaryngologist. When episodes of tonsillitis recur, acute tonsillitis diagnosis turns into recurrent tonsillitis (RT). Exacerbations of RT are treated with antibiotics. Currently, the frequency of exacerbations in the last 3 years is used as the main determining factor in the selection of patients for elective tonsillectomy. If there are 7 episodes of tonsillitis in a year, or 5 episodes of tonsillitis in a year for 2 consecutive years, or 3 episodes of tonsillitis in a year for 3 consecutive years, tonsillectomy is recommended. The etiopathogenesis of RT is not clear and is being actively studied. The reason for ineffective antibacterial therapy is explained by specific resistance mechanisms of bacteria, formation of biofilms, insufficient concentration of antibiotics in tonsillar tissue. RT reduces patients` quality of life and is a medical and a financial burden. During exacerbation of RT a peritonsillar abscess (PTA) as a complication may develop. Therefore, the aim of the study was to identify the etiological agents of RT and PTA in tonsil crypts and parenchyma samples, to determine antibacterial resistance and biofilm formation capacity of pathogenic bacteria, and to evaluate their importance in the pathogenesis and clinical course of RT and PTA. The study included several parts: 1st part was dedicated for evaluating RT and PTA patients undergoing tonsillectomy. The RT group consisted of 99 patients who underwent planned tonsillectomy due to RT despite appropriate antibacterial therapy. The PTA patient group consisted of 29 patients who underwent acute tonsillectomy for drainage of peritonsillar abscess. The objective of 2nd part was to evaluate the most accurate method of obtaining samples from tonsillar crypts. The study group of 25 patients with RT was created. In this part, tonsillar crypt samples were obtained in 2 ways and the results were compared. The objective of 3rd part was to evaluate the microbiological results of tonsillar crypt sample of healthy individuals. A group of healthy individuals without tonsillar pathology consisted of 91 participants – students of Medical Faculty of Rīga Stradiņš University. In 4th part a bacteriological evaluation of post-tonsillectomy patients was performed. The group consisted of 16 patients who previously had RT and had a tonsillectomy performed a year ago. These patients were subjected to clinical and bacteriological evaluation. During each part tonsillar crypt samples were taken for bacteriological analysis, antibacterial sensitivity and biofilm production capacity of isolated strains was assessed. The examinations were carried out in the laboratory of the Biology and Microbiology Department of Rīga Stradiņš University and the Laboratory of Bacteriology of the Pauls Stradiņš Clinical University Hospital. During the study a biopsy needle was developed and patented for obtaining an optimal sample of tonsillar crypts. The study found that RT patients, compared to PTA patients and healthy individuals, had a higher diversity of microorganisms in the tonsillar crypts, the predominant pathogen being S. aureus. Biofilm forming strains were detected in RT, PTA patients, but no significant antibacterial resistance was detected and no relationship between the biofilm producing phenotype and antibacterial sensitivity was observed. Clinically relevant pathogens (S. aureus, K. pneumoniae, P. aeruginosa) and susceptible biofilm producing strains were isolated from tonsillar crypts of healthy individuals without tonsillar pathology. The tonsillar crypts of healthy individuals are an important reservoir of pathogenic bacteria and biofilm producing strains. The results of our study confirm that tonsillectomy is effective in preventing bacterial colonization. The thesis is presented as a unifying material of peer-review publications, it summarizes the results of the research. The obtained results on RT and oral microbiota are of international importance and contain recommendations for use in clinical practice. 3.2 Clinical Medicine; Sub-Sector – Otorhinolaryngology. Keywords: recurrent tonsillitis, peritonsillar abscess, biofilms, antibacterial susceptibility.