The profiles of oral streptococci sensitivity to antibacterial drugs may reflect information about the presence of macroorganism resistance determinants. The aim of the work was to isolate the spectrum of oral streptococci from the microbiota of the oral cavity of patients and to determine their sensitivity to a wide range of antibiotics. A total of 342 microbial streptococcal isolates were isolated from saliva samples and a periodontal pocket and tested for antibiotic sensitivity. Species identification of streptococci was carried out using biochemical API test systems. Evaluation of antibiotic resistance was performed using E-tests. Real-time PCR was used to identify the presence of tetracycline and macrolide resistance genes. The study identified six types of oral streptococci: S. oralis, S. salivarius, S. mitis, S. sanguinis, S. anginosus and S. mutans. All streptococci were sensitive to linezolid and meropenem. The proportion of penicillin-resistant streptococci in the subgroup S. oralis / mitis / mutans was 47,8% versus 23,5% in the subgroup S. salivarius / sanguinis / anginosus (p = 0.020). Significant levels of resistance were revealed to macrolides (erythromycin) - 47,9%, tetracyclines (tetracycline) - 44,4% and quinolones (ofloxacin) - 41%. Multiple drug resistance (MDR) was detected in 31,9% of oral streptococcal isolates, a combination of erythromycin, tetracycline and ofloxacin resistance was prevalent in 79 isolates (23,1%). The most common genotypes of macrolides and tetracycline resistant oral streptococci (in 127 streptococcal isolates with combined resistance) were ermB-mefE + and tetM + tetQ-, respectively. Thus, S. oralis / mitis / mutans group streptococci predominated in the structure of antibiotic-resistant oral streptococci, including MDR. So, being in one of the most densely populated biotopes of a macroorganism, oral streptococci can mediate the transfer of resistance determinants to more pathogenic and clinically significant microorganisms, which requires careful monitoring of their level of susceptibility to antimicrobial agents.

The system of antimicrobial peptides (AMP) is one of the most ancient mechanisms of the macroorganism resistance to infectious pathogens invasion. The aim of the study was to determine the role of the antimicrobial peptides system and periodontal pathogenic markers in the development and progression of inflammatory periodontal diseases. Gingival pocket washes (91 samples in total) for the research were received from patients with inflammatory periodontal diseases (chronic periodontitis and gingivitis) and intact periodontium. Using ELISA, the content of antimicrobial peptides was determined: human alpha-defensin (HNP 1-3), beta-defensin (HBD 1-3) and cathelicidin (LL-37). Periodontal pathogenic markers were isolated during RT-PCR. The study revealed differences in AMP concentrations by groups: level of HBD 2 in patients with chronic periodontitis was 1,36 times higher than those in the group of patients with chronic gingivitis (p=0,023) and 2,39 times higher than those in the control group (p<0,001), the content of HNP 1-3 in the group of patients with chronic periodontitis was reduced by 1,23 times compared with the indicators of the group of patients with gingivitis (p=0,045) and by 1,97 times compared with the indicators of the control group (p<0,001). The frequency of detection of periodontal pathogenic bacteria genes was 88,0% in patients with periodontitis, 76,92% in patients with gingivitis and 33,3% in the group with intact periodontium. HBD 2 content moderately correlated with the definition of P. gingivalis (r=0,612; p=0,022), T. forsythensis (r= 0,434; p=0,015), A. actinomycetemcomitans (r=0,483; p=0,006), a moderate negative correlation was detected between the content of HNP 1-3 and the release of periodontal pathogens in associations (P. gingivalis with T. forsythensis and T. denticola) (r=-0,388; p=0,031) in the group of patients with chronic periodontitis. Thus, the revealed relationships and correlations indicate shifts in the processes of reparative regeneration of the oral cavity and the regulation of local immunity in response to microbial invasion.

Currently, the impact of antibiotic resistance on human health is a worldwide problem and its study is of great interest from a molecular genetic, environmental and clinical view-point. This review summarizes the latest data about antibiotic resistance, the classification of microorganisms as sensitive and resistant to the action of antibiotics, reveals the concept of minimum inhibitory concentration from modern positions. The resistance of microorganisms to antibacterial agents can be intrinsic and acquired, as well as being one of the examples of evolution that are currently available for study. Modern methods of whole-genome sequencing and complex databases of nucleotide-tagged libraries give an idea of the multifaceted nature of the mechanisms of intrinsic resistance to antibiotics and are able to provide information on genes encoding metabolic enzymes and proteins that regulate the basic processes of the physiology of bacteria. The article describes the main ways of spreading the resistance of microorganisms, reflects the concepts of “founder effect” and the fitness cost of bacteria, which underlie the emergence and evolution of antibiotic resistance. It is shown that the origin of antibiotic resistance genes that human pathogens currently possess can be traced by studying the surrounding not only clinical, but also non-clinical (ecological) habitats. As well as microorganisms of the surrounding ecosystems are the donors of resistance genes in horizontal gene transfer.