Incidence rates, emerging serotypes and genotypes, and antimicrobial susceptibility of pneumococcal disease in Taiwan: A multi-center clinical microbiological study after PCV13 implementation.

Objectives The multi-center clinical microbiological study in Taiwan aimed to evaluate the impact of childhood PCV13 immunization on pneumococcal disease, and the magnitude of serotype replacement in invasive and non-invasive pneumococcal disease among all age groups. Methods The study of culture-confirmed pneumococcal disease (CCPD) was conducted at four hospitals across Taiwan in 2015-2018. Pneumococcal pneumonia was defined as clinical diagnosis with positive sputum or bronchoalveolar lavage culture. Serotyping, multi-locus sequence typing, and antimicrobial susceptibility testing for penicillin and ceftriaxone were performed. Results A total of 1413 CCPD cases were identified. Invasive pneumococcal disease (IPD) accounted for 13.4% (190/1413) of CCPD. PCV7-type CCPD incidence declined among all age groups between 2015 and 2018. In adults aged 50-64 years, PCV7-type pneumococcal pneumonia incidence in 2018 was 72% lower than that in 2015, and all pneumococcal pneumonia incidence was 35% lower than that in 2015. In children, CCPD incidence was higher in 2018 than in 2015 (IRR 1.75 for age < 5 years, IRR 1.56 for age 5-17 years). Incidence of CCPD caused by non-PCV13-types, mainly 15A and 23A, increased significantly in those younger than 50 years. Serotypes 19A and 19F constituted the largest clonal complex, CC236/320 (n = 280, 19.8%). The rates of penicillin and ceftriaxone non-susceptibility were higher in PCV13-type isolates. Conclusions Childhood PCV13 immunization exerted an indirect protection to vaccine serotype clinically defined non-bacteremic pneumococcal pneumonia among adults, especially those between 50 and 64 years of age. Emerging non-PCV13 serotypes mainly caused non-invasive mucosal disease among children.