title: Analysis of Haemophilus influenzae serotype f isolated from three Japanese children with invasive H. influenzae infection.
abstract: In Japan, publicly subsidized Haemophilus influenzae serotype b vaccines became available in 2011; consequently, the incidence of invasive H. influenzae infection in paediatric patients of less than 5 years of age decreased dramatically. In 2013, the first case of H. influenzae serotype f (Hif) meningitis in a Japanese infant was reported, and another case of Hif meningitis in a Japanese infant was observed in 2013. We experienced a fatal paediatric case of Hif bacteraemia in 2004; therefore, we conducted an analysis of the three Hif strains isolated from these three Japanese children with invasive Hif infections. All three strains were β-lactamase-non-producing, ampicillin-sensitive strains, with MICs of 1 µg ml(-1) or less. However, one of the three strains showed slightly elevated MICs for ampicillin (1 µg ml(-1)), cefotaxime (0.25 µg ml(-1)) and meropenem (0.13 µg ml(-1)). A molecular analysis by multilocus sequence typing identified all three strains as sequence type (ST) 124, which is a predominant invasive Hif strain in many countries. SmaI-digested PFGE showed variable DNA fragmentation patterns among the strains, suggesting that some highly virulent strains have originated from a single ST124 clone and caused invasive Hif infections in Japan. Additional studies are needed to determine the factors that have led to the clonal expansion of virulent ST124 strains.
authors: Division of Infectious Diseases, Chiba Children's Hospital, Chiba, Japan.
authors: Tadashi
authors: T
authors: Hoshino
authors: Chiba Prefectural Institute of Public Health, Chiba, Japan.
authors: Yushi
authors: Y
authors: Hachisu
authors: Chiba Prefectural Institute of Public Health, Chiba, Japan.
authors: Takashi
authors: T
authors: Kikuchi
authors: Division of Infectious Diseases, Chiba Children's Hospital, Chiba, Japan.
authors: Shoko
authors: S
authors: Tokutake
authors: Division of Infectious Diseases, Chiba Children's Hospital, Chiba, Japan.
authors: Hideyuki
authors: H
authors: Okui
authors: Division of Infectious Diseases, Chiba Children's Hospital, Chiba, Japan.
authors: Satoru
authors: S
authors: Kutsuna
authors: Division of Infectious Diseases, Chiba Children's Hospital, Chiba, Japan.
authors: Chie
authors: C
authors: Fukasawa
authors: Department of Metabolism, Chiba Children's Hospital, Chiba, Japan.
authors: Kei
authors: K
authors: Murayama
authors: Children's Medical Center, Fujisawa City Hospital, Kanagawa, Japan.
authors: Asami
authors: A
authors: Oohara
authors: Children's Medical Center, Fujisawa City Hospital, Kanagawa, Japan.
authors: Hiroyuki
authors: H
authors: Shimizu
authors: Department of Pediatrics, Nagoya City West Medical Center, Aichi, Japan.
authors: Midori
authors: M
authors: Ito
authors: Department of Pediatrics, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Yoshiko
authors: Y
authors: Takahashi
authors: Department of Infectious Diseases, Medical Mycology Research Center, Chiba University, Chiba, Japan.
authors: Naruhiko
authors: N
authors: Ishiwada
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology*; D002675:Child, Preschool; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D006193:Haemophilus influenzae / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*; D006801:Humans; D007223:Infant; D007564:Japan / Q000453:epidemiology; D008583:Meningitis, Haemophilus / Q000453:epidemiology / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D065288:Serogroup; D001618:beta-Lactamases / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D000667:Ampicillin; D001618:beta-Lactamases