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A hospital-associated outbreak of Legionnaires' disease caused by Legionella pneumophila serogroup 1 is characterized by stable genetic fingerprinting but variable monoclonal antibody patterns.

Abstract

An outbreak of 18 pneumonia cases caused by Legionella pneumophila serogroup 1 occurred at a Swedish university hospital 1996 to 1999. Eight clinical isolates obtained by culture from the respiratory tract were compared to 20 environmental isolates from the hospital and to 21 epidemiologically unrelated isolates in Sweden, mostly from patients, by using pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphism analysis (AFLP), and monoclonal antibody (MAb) typing. All patients and most environmental isolates from the outbreak hospital belonged to the same genotypic cluster in both PFGE and AFLP. This genotype was distinctly different from other strains, including a cluster from a second hospital in a different part of the country. The MAb subtype of the outbreak clone was Knoxville except for three isolates that were Oxford. A variation in the MAb reactivity pattern was also found in a second genotypic cluster. These changes in the MAb reactivity pattern were due to the absence or presence of the lag-1 gene coding for an O-acetyltransferase that is responsible for expression of the lipopolysaccharide epitope recognized by MAb 3/1 of the Dresden Panel. In all MAb 3/1-positive strains, the lag-1 gene was present on a genetic element that was bordered by a direct repeat that showed a high degree of sequence homology. Due to this homology, the lag-1 gene region seemed to be an unstable element in the chromosome. MAb patterns are thus a valuable adjunct to genotyping methods in defining subgroups inside a genotypic cluster of L. pneumophila sg 1.

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    • Authors

    Bernander S, Jacobson K, Helbig JH, Lück PC, Lundholm M

    Institution

    Department of Clinical Microbiology, Karolinska Hospital, and Microbiology and Tumor Biology Center, MTC, Karolinska Institute, Stockholm, Sweden. sverker.bernander@ks.se

    Source

    Journal of clinical microbiology 41:6 2003 Jun pg 2503-8

    MeSH

    Acetyltransferases
    Antibodies, Bacterial
    Antibodies, Monoclonal
    Bacterial Typing Techniques
    DNA Fingerprinting
    Disease Outbreaks
    Electrophoresis, Gel, Pulsed-Field
    Hospitals, University
    Humans
    Legionella pneumophila
    Legionnaires' Disease
    Polymorphism, Restriction Fragment Length
    Serotyping

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    12791873