Objectives Domestic epidemiological studies are needed to ascertain the disease burden of bacteraemia in individual countries. This study aimed to evaluate the domestic trends in paediatric and adult bacteraemia in Japan. Setting Laboratory-based surveillance was used to obtain data from 592 hospitals located throughout Japan. Participants The study was conducted using the results of 827 780 and 3 512 524 blood culture tests obtained from children and adults, respectively, between January 2010 and December 2016. Outcome measures We analysed the temporal trends in specific bacterial species (Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Haemophilus influenzae, Listeria monocytogenes and Neisseria meningitidis) detected from the blood cultures of children and adults. For children aged ≤2 years, the data were analysed for each year of age. The proportions of bacteraemia-positive results among the patients were also evaluated. Results The number of bacteraemia-positive samples over the study period was 47,125/827,855 (5.7%) in children and 959,765/3,513,885 (27.3%) in adults. S. pneumoniae was the most frequent cause of bacteraemia in children in 2010. However, after 2011, S. aureus bacteraemia was the most frequent, followed by S. pneumoniae and E. coli. E. coli bacteraemia showed significant increases in both children and adults. In children, S. pneumoniae and H. influenzae bacteraemia decreased from 2010 to 2013. However, S. pneumoniae bacteraemia case numbers stabilised from 2013, whereas H. influenzae bacteraemia cases continued to decrease until 2016. Conclusion The results suggest that the introduction of the 13-valent pneumococcal conjugate vaccine did not substantially affect disease occurrence. In contrast to the decreasing trends in H. influenzae and S. pneumoniae bacteraemia, S. aureus, E. coli and S. agalactiae bacteraemia showed increasing trends. These findings shed light on recent temporal trends in bacteraemia in both children and adults in Japan.
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