INTRACELLULAR GROWTH OF LEGIONELLA-PNEUMOPHILA SEROGROUP-1 MONOCLONAL-ANTIBODY TYPE-2 POSITIVE AND NEGATIVE BACTERIA

Epidemiological evidence suggests that monoclonal antibody type 2 posi tive (MAB 2+) Legionella pneumophila serogroup 1 (LP1) more often caus es disease than do MAB 2- isolates, and there is evidence that MAB 2- LP1 grow less well in cells than do MAB 2+ bacteria. We tested the int racellular growth rates of ten randomly selected MAB 2- LP1 isolates, by using guinea-pig alveolar macrophages, and human monocyte-derived m acrophages. Save a low virulence control, all ten MAB 2- isolates grew as well in cells as a virulent MAB 2+ isolate. Heterogeneity of MAB 2 - LP1 growth in cells exists, making poor intracellular growth an unli kely explanation for why MAB 2+ LP1 appear to cause disease more often .