Multiple clonal types of nonvaccine serotypes constitute β-lactams nonsusceptible pneumococcus isolates from adult pneumonia patients in Japan

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background and objective </jats:bold>The global spread of antimicrobial-nonsusceptible <jats:italic>Streptococcus pneumoniae </jats:italic>is a major concern. Molecular epidemiology of those strains in relation to vaccine serotype remains to be explored in Japan. This study aimed to elucidate the distribution of molecular types with the serotypes and antimicrobial susceptibility of pneumococcus strains isolated from adult pneumonia patients. <jats:bold>Methods </jats:bold>We enrolled adult pneumonia patients from four sites in Japan between September 2011 and August 2014. <jats:italic>S. pneumoniae</jats:italic> isolates from sputum and blood were analyzed for serotyping by the Quellung reaction and for antimicrobial susceptibility by the agar dilution method and e-test and for multilocus sequence typing. <jats:bold>Results </jats:bold>In total, 204 isolates were analyzed from 200 patients with a median age of 72.5 years, of whom 55 (27.5%) patients had received a 23-valent pneumococcal polysaccharide vaccine (PPSV23). We detected 41 clonal complexes (CCs) and 62 sequence types (STs), including 10 new STs: CC/ST 180 of serotype 3 was the most common followed by CC/ST 236 of serotype 19F and CC/ST 99 of serotype 11A; 144 (70.6%) isolates were PPSV23 serotypes; 40 (19.6%) and 121 (59.3%) isolates were b-lactam nonsusceptible (bNS) and multidrug-nonsusceptible strains, respectively. Among the bNS strains, 18 (45%) were nonvaccine serotypes, and 4 CCs (CC236, CC63, CC242, and CC558) comprised of 62.5% of them.<jats:bold>Conclusion </jats:bold>Multiple CCs of bNS strains, including nonvaccine serotype are spreading. It is crucial to monitor the antimicrobial susceptibility, serotypes, and molecular types of pneumococci to predict the effectiveness of vaccines in preventing pneumonia by bNS pneumococci strains.</jats:p>