title: Sero diagnosis of Legionella infection in community acquired pneumonia.
abstract: OBJECTIVE
  Legionella pneumophila has been increasingly recognized as an emerging pathogen responsible for community acquired pneumonia (CAP) worldwide. In India, the actual burden is not known. The present study was thus undertaken to see the presence of Legionella infection in patients with community acquired pneumonia admitted in a tertiary care centre in north India.
  
  
  METHODS
  Both children and adults (n=113) with symptoms of pneumonia were included in the study. Clinical samples (blood, urine, nasopharyngeal aspirates, bronchoalveolar lavage, sputum, etc.) were collected and subjected to culture and other tests. Enzyme linked immunosorbent assay (ELISA) was done by commercial kits for all the three classes of immunoglobulins (IgG, IgM & IgA). Urinary antigen was also detected using commercial kits. Culture was performed on 51 respiratory tract fluid samples. Serum samples of 44 healthy controls were also screened for the presence of anti-legionella antibodies (IgG, IgM & IgA).
  
  
  RESULTS
  Thirty one of the 113 cases (27.43%) were serologically positive. Anti-legionella IgG, IgM and IgA antibodies were positive in 7.96, 15.92 and 11.50 per cent patients respectively. In controls, seropositivity was 9.09 (4/44). IgA was positive in 3 and IgM, IgG combined in one. Antigenuria detection by Microwell ELISA kit showed 17.69 per cent positivity. Four antigenuria positive patients were also serologically positive; of these two patients were positive for IgM, hence considered as confirmed cases of Legionella infection. None of the sample was culture positive.
  
  
  CONCLUSIONS
  Combination of serology and antigenuria detection may be a valuable tool for the diagnosis of Legionella infection in absence of culture positivity. In order to evaluate the actual burden of Legionella in community acquired pneumonia, further studies with larger samples need to be done.
authors.affiliation: Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Sabah
authors.initials: S
authors.lastname: Javed
authors.forename: Rama
authors.initials: R
authors.lastname: Chaudhry
authors.forename: Kapil
authors.initials: K
authors.lastname: Passi
authors.forename: Sutikshan
authors.initials: S
authors.lastname: Sharma
authors.forename: Padmaja
authors.initials: P
authors.lastname: K
authors.forename: Benu
authors.initials: B
authors.lastname: Dhawan
authors.forename: A B
authors.initials: AB
authors.lastname: Dey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007223:Infant; D016952:Legionella pneumophila / Q000276:immunology; D007877:Legionnaires' Disease / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D012698:Serologic Tests; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial