Serotype prevalence and antibiotic susceptibility patterns of pneumococcal isolates in Zunyi city, China

Objectives: To assess the serotype distribution and antimicrobial susceptibility of pneumococci isolated from inpatients of all ages suspected of having bacterial infections. Methods: In this retrospective study, pneumococcal isolates were consecutively collected from the Third Affiliated Hospital of Zunyi Medical University, in Zunyi city, China, between January 2014 and December 2016. Pneumococci were identified using routine microbiological assays. We performed antimicrobial susceptibility analyses using the bacteria identification/susceptibility system VITEK2 and E-tests. Capsular types of all isolates were determined by multiplex polymerase chain reaction. Results: We identified 778 pneumococcal isolates. Serotypes 19F, 6A/6B, 19A, 23F, and 15B/15C were the most prevalent strains, accounting for 71.5% (556/778) of all isolates. Data show that 409 (70.4%) isolates could be covered by the PCV13 vaccine in children less than 2 years old. Irrespective of serotypes, 747 (96%) isolates were sensitive to penicillin, while 720 to 778 (90% to 100%) isolates were not susceptible to erythromycin, tetracycline, and trimethoprim/sulfamethoxazole. For isolates resistant to penicillin, ceftriaxone, cefotaxime, and meropenem, 22 to 39 (70% to 81.25%) strains belonged to PCV13 serotypes. Conclusion: We found a substantial increase in the annual number of pneumococcal isolates since 2014. The theoretical impact of PCV13 was high in children less than 2 years old, and penicillin might be effective against pneumococcal infections in this region.