Serodiagnosis of atypical bacterial respiratory infections

Since prevalence of antibodies to bacteria causing atypical respiratory infections in Israel is as yet unknown, a 5-year antibody prevalence study was performed. Seroreactivity to Chlamydia pneumoniae (TWAR), with titers > or = 1:16 by microimmunofluorescence assay (MIF) was detected in 725/1305 (55.5%) of patients. 47/1012 ((4.6%) of adult patients had MIF results indicating recent infection with TWAR, (IgG titers of > or = 1:512, and/or IgM titers of > or = 1:16, and/or seroconversion). Antibody prevalence and titers were low in children aged 1-10 years, increased in teenagers, and peaked in adults and the elderly, in whom prevalence was up to 79% and mean geometric titer up to 1:163. Unlike the consistency in TWAR antibody prevalence and serological evidence of recent infection during the study period, a significant decrease in those variables was observed for Chlamydia trachomatis during the first 3 study years. Antibodies to M. pneumoniae were detected in 53 and to Legionella sp. in 47 out of 763 patients. There was serological evidence of recent infection with M. pneumoniae in 10 (including 7 children) and with Legionellae in 8. Improved diagnosis of atypical respiratory infection might be achieved by the combined use of these proposed serological procedures.