Problem of immunoglobulin M co-detection in serological response to bacterial and viral respiratory pathogens among children suspected of legionellosis

The objective of this research was an analysis of the serological response to respiratory bacterial and viral pathogens, in 156 children admitted to hospital in Warsaw with a suspicion of legionellosis. Levels of immunoglobulin (Ig) M to Bordetella pertussis, Mycoplasma pneumoniae, respiratory syncytial virus (RSV), adenoviruses, human parainfluenza virus (HPIV) t. 1-4 and influenza t. A + B viruses were determined retrospectively by ELISAs. In the prospective examinations (only Legionella pneumophila sg1), a positive level of IgM was found in 35 patients, but in 59 children together with retrospective tests. There were positive results for B. pertussis (21 children), followed by HPIV (10 children), M. pneumoniae (5 patients), RSV (4 persons), adenoviruses (3 children), and influenza A + B virus (3 persons). Positive results for > 1 agent were found in 16 children. The most often co-detected IgM were to L. pneumophila sg1 and B. pertussis (9 children) and L. pneumophila sg1 and M. pneumoniae (5 patients). The distribution of IgM to L. pneumophila sg1, B. pertussis and HPIV among children ≤ 4 years differed significantly from IgM specific to other pathogens. A high number of HPIV infections, mainly single, was found among infants. Positive results of IgM to L. pneumophila sg1 were mainly found in children aged 4-5 years. and the oldest children (over 10 years.). However, among the oldest children, anti-L. pneumophila sg1 antibodies were often found together with IgM to B. pertussis. Infections due to more than 2 pathogens were only observed among patients with pneumonia, especially due to L. pneumophila sg1 and/or B. pertussis. Conversely, co-detection of IgM ELISA for L. pneumophila and M. pneumoniae were mainly detected among patients hospitalized without pneumonia.