Studies on the etiology of lower respiratory infectionsAs a contribution to knowledge about the etiology of lower respiratory tract infections (LRI) in infants, 235 patients aged one year or less admitted to a children's hospital at northern metropolitan area of Santiago, Chile along years 1987 throughout 1989 with radiologically confirmed diagnosis were studied. Infants were eligible only if their symptoms lasted for not more than five days and their hospital stay was less than two days. Controls consisted on 74 healthy infants. A search for presumtive etiology was done by means of usual bacteriological procedures {pharyngeal swabs and blood cultures), plus latex test for type b Haemophitus influanzae (Hib) and Streptococcus pneumoniae (SP* in concentrated urine specimens; indirect inmunofluorescence (IF) for specific Chlamydia tracbomatis