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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 b-lactamase-non-producing, ampicillinsensitive strains, with MICs of 1 mg ml "1 or less. However, one of the three strains showed slightly elevated MICs for ampicillin (1 mg ml "1 ), cefotaxime (0.25 mg ml "1) and meropenem (0.13 mg 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.

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Background: Pediatric parapneumonic effusion/ pleural empyema (PPE/PE) is a severe infectious condition, and its management should be guided by local epidemiology and the patient's medical history. This survey aimed to determine the clinical and bacteriologic features of PPE/PE in Japan. Methods: A nationwide retrospective questionnaire survey was conducted, targeting 159 pediatric specialist training medical facilities for inpatients ≤18 years of age who were admitted for PPE/PE between January 2007 and December 2016. Results: Valid responses were obtained from 122 facilities, and 96 patients were identified from 38 facilities. The median age (interquartile range) was 2.7 (0.8-7.8) years. Overall, 60 (63 %) patients were men and 49 (51%) had comorbidities. The causative bacteria were identified in 59% of patients by culture except in one case identified using PCR. Streptococcus pyogenes (16%), Staphylococcus aureus (14%) and Streptococcus pneumoniae (13%) were the major pathogens. Carbapenems were administered to 34% of patients without comorbidities. Chest tube drainage was performed in 71%, intrapleural fibrinolytic therapy in 9.4%, surgery in 25% and mechanical ventilation in 29% of the patients. Five patients (5.2%) had complications and one (1.1%) had sequelae, but all patients (100%) survived. Conclusions: This is first report of a nationwide survey pertaining to pediatric PPE/PE in Japan. We found that the etiology showed a different trend from that reported in other countries. It is worrisome that molecular methods were rarely used for pathogenic diagnosis and carbapenems were overused. Thus, it is imperative to establish clinical guidelines for PPE/PE in Japan.

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