The enzyme linked immunosorbent assay (ELISA) described was developed to detect a soluble antigen in the urine of

The detection of Legionella pneumophila DNA in clinical specimens using quantitative real-time polymerase chain reaction (qPCR) combined with direct sequence-based typing (SBT) offers rapid confirmation and timely intervention in the investigation of cases of Legionnaires' disease (LD). We assessed the utility of a specific L. pneumophila qPCR assay targeting the macrophage infectivity potentiator (mip) gene and internal process control with three clinical specimen types from confirmed LD cases. The assay was completely specific for L. pneumophila, as demonstrated by positive results for 39/39 strains from all subspecies and 16 serogroups. No cross-reaction was observed with any of the 54 Legionella non-pneumophila (0/69 strains) or 21 non-Legionella (0/58 strains). All L. pneumophila culture-positive respiratory samples (81/81) were qPCR-positive. Of 80 culture-negative samples tested, 47 (58.8%) were qPCR-positive and none were inhibitory. PCR was significantly more sensitive than culture for samples taken ≤ 2 days of hospitalisation (94.7% vs. 79.6%), with the difference being even more marked for samples taken between 3 and 14 days (79.3% vs. 47.8%). Overall, the sensitivity of the qPCR was ∼30% greater than that of culture and direct typing on culture-negative PCR-positive samples resulted in full 7-allele profiles from 23/46, 5 to 6 alleles from 8/46 and ≥ 1 allele from 43/46 strains.

Summary. Monoclonal antibody (MAb) to diphtheria toxin was produced in mouse hybridomas, and shown by ELISA to be of sub-class IgG,. Hybridomas were inoculated into mice to produce ascitic fluid from which MAb was purified by caprylic acid. The MAb was shown by immunoblotting to be directed against the A fragment of the toxin and also against the intact toxin molecule. After conjugation with fluorescein isothiocyanate, it was used in an immunoassay to detect toxin in culture supernates of Corynebacteriurn diphtheriae and C. ulcerans. The assay correlated well with the Elek test and with virulence in guinea-pigs; but it gave occasional false positive results, probably by binding of MAb to defective toxin.

Formolised yolk sac antigens of Legionella pneumophila serogroups 1-6 were used to test 1792 serum specimens from 1431 patients with respiratory illness of serological evidence of Legionnaires' disease (LD). Thirty-five patients showed titres against the serogroup 1 antigen diagnostic for LD. Only two further cases were considered to have non-serogroup I infections (both serogroup 4) indicating that such infections are rare. Titres of greater than 1/16 against the serogroup 1 antigen occur in only 3% of subjects without LD and thus the demonstration of such a titre in patients with pneumonia during the early phase of illness can alert the clinician to the likelihood of LD. The supply of serogroup 1 antigen from the Division of Microbiological Reagents and Quality Control to routine diagnostic laboratories will be continued and monovalent serogroup 2-6 antigens will continue to be made available to reference laboratories.

SUMMARY The sensitivity of an indirect immunofluorescence antibody test (IFAT) and a rapid microagglutination test (RMAT) for the diagnosis of Legionnaires' disease caused by Legionella pneumophila serogroup 1 was evaluated using serum specimens from 119 patients with bacteriologically confirmed infections. The sensitivity of both assays was found to be about 80%. In addition, antibody titres suggestive of L pneumophila infection were found in 40% of patients in the first week after admission to hospital. These data show that both assays can be used with confidence in the early diagnosis of Legionnaires' disease.