Spectrum and resistance determinants of oral streptococci clinical isolates

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.