Nationwide survey of the development of drug resistance in the pediatric field in 2007 and 2010: drug sensitivity of Haemophilus influenzae in Japan (second report)

The Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease conducted national surveillance for Haemophilus influenzae in 2007 (phase 3) and 2010 (phase 4), following the previous surveillance conducted from 2000 to 2001 (phase 1) and in 2004 (phase 2). We examined the antimicrobial susceptibility for H. influenzae derived from clinical specimens of pediatric patients collected nationwide from 27 institutions during phases 3 (386 strains) and 4 (484 strains). The frequency of beta-lactamase-nonproducing ampicillin (ABPC)-resistant (BLNAR) strains, which rapidly increased from 11.4 % in phase 1 to 43.4 % in phase 2, has gradually decreased from 38.3 % in phase 3 to 37.8 % in phase 4. In contrast, On the other hand, the frequency of beta-lactamase-producing strains, which continuously decreased from 8.3 % in phase 1 to 4.4 % in phase 3, has increased to 8.7 % in phase 4. Prevalence of beta-lactamase-producing clavulanic acid/amoxicillin-resistant (BLPACR) strains, especially, has increased from 1.6 % in phase 3 to 4.8 % in phase 4. The oral antimicrobial agents with the lowest MIC90 were levofloxacin in both phases, and tosufloxacin in phase 4 (a parts per thousand currency sign0.063 mu g/ml), whereas for intravenous use the corresponding agent was tazobactam/piperacillin in both phases (0.125 mu g/ml). There was no increase in the MIC90 of most beta-lactams between phase 3 and phase 4. In relationship to sex, age, presence of siblings, attendance at a daycare center, siblings' attendance at a daycare center, and prior administration of antimicrobial agents within 1 month, the frequency of beta-lactamase-nonproducing ABPC-intermediately resistant (BLNAI) strains + BLNAR strains was high (P = 0.005) in cases with prior administration of antimicrobial agents in phase 3.