Antimicrobial resistance of Streptococcus pneumoniae in adults with community-acquired pneumonia in Kazan before and during the COVID-19 pandemic

BACKGROUND: Diseases caused by Streptococcus pneumoniae remain one of the leading causes of infectious disease–related mortality in Russia and worldwide. The COVID-19 pandemic, accompanied by increased use of antibacterial agents for the treatment of respiratory tract infections, has affected both the spectrum of pathogens and the trends of antimicrobial resistance. However, findings vary across different regions. AIM: The study aimed to investigate trends in the frequency of pneumococcus strains resistant to antimicrobial agents in adults with community-acquired pneumonia in Kazan from 2019 to 2022. METHODS: It was a retrospective observational study of pneumococcal antimicrobial resistance using data from the Laboratory Diagnostic Center of the Republican Clinical Infectious Diseases Hospital named after Professor A. F. Agafonov. Sputum samples from adults with community-acquired pneumonia were collected from 11 medical institutions in Kazan between 2019 and 2022. Antimicrobial resistance was determined by the disk diffusion method and interpreted according to the Russian guidelines Determination of Microorganism Susceptibility to Antimicrobial Agents. The frequency of resistant pneumococcus strains and changes in resistance profiles were assessed. In addition, a retrospective analysis of the incidence of bacterial pneumonia in Kazan from 2019 to 2024 was performed. RESULTS: From 2019 to 2024, the incidence of bacterial community-acquired pneumonia among the adult population in Kazan increased from 76.8 per 100,000 population (95% CI, 71.3–82.3) to 88.3 per 100,000 (95% CI, 82.4–94.2) (p = 0.002). The highest and the lowest incidences were observed in 2024 and 2021, respectively. Among the 196 Streptococcus pneumoniae isolates studied, the proportions of resistant strains were as follows: penicillin, 38.3% (95% CI, 31.5–45.1); erythromycin, 26.0% (95% CI, 19.8–32.2); levofloxacin, 10.7% (95% CI, 6.1–15.3); clindamycin, 16.8% (95% CI, 11.5–22.1); tetracycline, 22.3% (95% CI, 14.1–28.5); and co-trimoxazole, 30.8% (95% CI, 24.3–37.3). CONCLUSION: A high proportion of pneumococcus strains resistant to major classes of antibacterial agents was identified. During the peak years of the COVID-19 pandemic (2020–2022), no significant changes were observed in the frequency or resistance profiles of pneumococcus strains isolated from patients with community-acquired bacterial pneumonia compared with 2019.