Changes in the lag-1 Locus of Legionella pneumophila Serogroup 1 Strains Result in Different Lipopolysaccharides Recognized by Monoclonal Antibodies but Do Not Influence Virulence

It is well established that Legionella pneumophila is an important cause of nosocomial and community-acquired pneumonia. L. pneumophila serogroup 1, the most prevalent serogroup, can be divided into several subtypes by using monoclonal antibodies (MAb). Researchers showed recently that changes in the lipopolysaccharide (LPS) MAb binding patterns are associated with changes in the virulence properties of L. pneumophila. Several studies showed that a majority of clinical isolates, especially strains associated with outbreaks, carried an LPS epitope that reacts with MAb 2 of the international standard panel and the MAb 3/1. Researchers used genetic fingerprinting to investigate several L. pneumophila serogroup 1 strains originated from the same source that differed in their reactivity with MAb 3/1 but were indistinguishable or very similar. Furthermore, researchers investigated whether the loss of the reactivity with MAb 3/1 resulted in differences in the multiplication in Acanthamoeba castellanii and macrophage cells. The lag-1 gene was amplified from chromosomal DNA and sequenced using an ABI 377 sequencer.