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Article in Japanese

Antimicrobial susceptibility and serotypes of Haemophilus influenzae isolated from pediatric patients at Chiba Children's Hospital between 2013 and 2016

Shota YAMAMOTO1), Chie FUKASAWA1), Taizo KUSANO1), Kenichi TAKESHITA1), Tadashi HOSHINO1)

This study examined the antimicrobial susceptibility and serotypes of 926 Haemophilus influenzae isolates obtained from pediatric patients between 2013 and 2016. The percentage distribution of β-lactamase-non-producing ampicillin-resistant strains was 35.7%, which had not increased from that obtained in the authors' previous study after 2000. However, the percentage of β-lactamase-producing strains did increase. Tosufloxacin (≤0.06μg/mL) and tazobactam/piperacillin (≤0.13μg/mL) exhibited a low 90% minimum inhibitory concentration against H. influenzae, however, 3 highly-resistant strains to tosufloxacin (≥16μg/mL) were observed. Only 2 non-typeable and all the serotyped strains were obtained from sterile and non-sterile sites, respectively. Serotype b strains (Hib) comprised only 2 of the 926 isolates; with their distribution dramatically decreased from that observed in the previous study after 2000. On the other hand, non-serotype b-capsulated strains were identified in 28 isolates, and 14 of them were serotyped as type e, whereas, the other 14 were serotyped as type f; and their distribution did not increase. Serotype replacement was not observed. For now, we do not need to change the therapeutic strategy against H. influenzae, and there is few risk of invasive infection of non-Hib strains. However, we need to continue to monitor the antimicrobial susceptibility and serotypes of H. influenzae.

1) Division of Infectious Diseases, Chiba Children's Hospital

Key words Haemophilus influenzae, antimicrobial susceptibility, serotypes
Received April 26, 2018
Accepted December 27, 2018

31 (2):85─94,2019