Antibiotic susceptibility in relation to genotype of Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae responsible for community-acquired pneumonia in children

Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae are the main pathogens causing community-acquired pneumonia (CAP). We identified S. pneumoniae (n = 241), H. influenzae (n = 123), and M. pneumoniae (n = 54) as causative pathogens from clinical findings and blood tests from pediatric CAP patients (n = 903) between April 2008 and April 2009. Identification of genes mediating antimicrobial resistance by real-time PCR was performed for all isolates of these three pathogens, as was antibiotic susceptibility testing using an agar dilution method or broth microdilution method. The genotypic (g) resistance rate was 47.7 % for penicillin-resistant S. pneumoniae (gPRSP) possessing abnormal pbp1a, pbp2x, and pbp2b genes, 62.6 % for β-lactamase-nonproducing, ampicillin-resistant (gBLNAR) H. influenzae possessing the amino acid substitutions Ser385Thr and Asn526Lys, and 44.4 % for macrolide-resistant M. pneumoniae (gMRMP) possessing a mutation of A2063G, A2064G, or C2617A. Serotype 6B (20.3 %) predominated in S. pneumoniae, followed by 19F (15.4 %), 14 (14.5 %), 23F (12.0 %), 19A (6.2 %), and 6C (5.4 %). Coverage for the isolates by heptavalent pneumococcal conjugate vaccine (PCV7) and PCV13, respectively, was calculated as 68.5 and 80.9 %. A small number of H. influenzae were identified as type b (6.5 %), type e (0.8 %), or type f (0.8 %); all others were nontypeable. Proper use of antibiotics based on information about resistance in CAP pathogens is required to control rapid increases in resistance. Epidemiological surveillance of pediatric patients also is needed to assess the effectiveness of PCV7 and Hib vaccines after their introduction in Japan.