Mycoplasma pneumoniae and other pathogens in the aetiology of lower respiratory tract infections among Japanese children

The causes of lower respiratory tract infections in 1544 children attending a Japanese hospital over a period of 7 years were investigated. Both cultivation and two serological techniques were used to detect Mycoplasma pneumoniae whereas viral involvement was investigated only by serology. Pathogens were identified in 52 % of 1175 patients with pneumonia and 36% of 369 patients without pneumonia. Mycoplasma pneumoniae infection was specifically diagnosed in 414 (26·8 %) of the 1544 patients. Respiratory syncytial virus (RSV) was dominant in children up to 2 years of age. By the age of 3 years, M. pneumoniae was equalling it in incidence and became the main pathogen in older groups. It is suggested that M. pneumoniae may be more important in the 3–6 years age group than hitherto suspected. These observations may influence the choice of antibiotics for treating lower respiratory tract infections in childhood.