[Antimicrobial susceptibility of Haemophilus influenzae isolated from pediatric patients at a pediatric facility between 2009 and 2012].

We examined the antimicrobial susceptibility of 1,208 Haemophilus influenzae isolates obtained at a pediatric facility between 2009 and 2012. The percentage distribution of beta-lactamase-non-producing ampicillin (ABPC)-sensitive (BLNAS) strains was 38.2%, that of beta-lactamase-non-producing ABPC-intermediately resistant (BLNAI) strains was 13.9%, that of beta-lactamase-non-producing ABPC-resistant (BLNAR) strains was 38.2%, that of beta-lactamase-producing ABPC-resistant (BLPAR) strains was 5.2%, and that of beta-lactamase-producing clavulanic acid/amoxicillin-resistant (BLPACR) strains was 4.5%. Although the percentage of BLNAR strains increased dramatically from 13.9% (2000-2003; period I) to 32.7% (2004-2008; period II), it increased more slowly from period II to the present period (2009-2012). However, the percentage of BLNAI strains, which had decreased from 10.6% (period I) to 8.9% (period II), began to increase during the present period. Tosufloxacin (< or = 0.06 microg/mL) and tazobactam/piperacillin (< or = 0.13 microg/mL) exhibited a low 90% minimum inhibitory concentration for H. influenzae, as well as for BLNAR strains. A decreased susceptibility to cephems was also observed throughout all 3 periods. Serotype b strains (Hib) were observed in 54 of the 1,208 isolates (4.5%); their distribution decreased since period II (6.3%). In Hib, the percentage distribution of strains from patients less than 2 years of age, who are recommended to be vaccinated against Hib, decreased from 56.8% to 29.6%, and this reduction seems to have been achieved by increasing the percentage of Hib vaccine inoculations in Japan. Non-serotype b-capsulated strains were identified in 21 isolates (1.7%), and 11 of them were serotyped as type e, whereas the other 10 were serotyped as type f.