Drug-resistant genes and serotypes of pneumococcal strains of community-acquired pneumonia among adults in Japan

Background: A high frequency of drug-resistant pneumococci has been reported in Asian countries. Few data on the drug-resistance or serotype of pneumococcal strains responsible for community-acquired pneumonia (CAP), however, are available for the past two decades in Japan. Methodology: Susceptibility to antibiotics and the genotype of antibiotic-resistant genes and serotypes of Streptococcus pneumoniae isolates from 114 adult patients with CAP were examined in a nationwide study in Japan between 2001 and 2003. Results: Most of the cases were non-bacteraemic pneumonia and the case fatality rate was 4.4%. The most frequent genotype of the pbp gene was pbp1a + 2x + 2b (gPRSP; 36.8%) followed by pbp 2x (28.1%) and of the macrolide-resistant gene, it was ermB (50.0%). The most common serotype was 19F (29.1%), followed by serotype 23F (13.2%), 6B (12.3%) and 3 (11.4%). The coverage of serotypes of isolates by a 23-valent pneumococcal polysaccharide vaccine (PPV) would be 82.5% in these patients with CAP. Most of strains with serotypes 19F and 23F were gPRSP. A cluster of serotype 3 strains associated with the pbp 2x and ermB gene was also noted. Conclusion: A high frequency of altered pbp gene mutations or of macrolide-related genes and a high serotype coverage by the 23-valent PPV found in our study of pneumococcal pneumonia facilitates attempts to increase the coverage rate of the 23-valent PPV in adults older than 65 years in Japan.