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  • Title: Heterogeneity in chlorine susceptibility for Legionella pneumophila released from Acanthamoeba and Hartmannella.
    Author: Chang CW, Kao CH, Liu YF.
    Journal: J Appl Microbiol; 2009 Jan; 106(1):97-105. PubMed ID: 19040705.
    Abstract:
    AIMS: To assess chlorine susceptibility of Legionella pneumophila grown from two amoebic hosts, Acanthamoeba castellanii and Hartmannella vermiformis. METHODS AND RESULTS: After being released from amoebae, Leg. pneumophila were chlorinated at 2 and 5 mg l(-1) for 5 min-24 h. Bacterial culturability and cytoplasmic membrane deterioration were quantified by culture assay on BCYEalpha agar and BacLight stains coupled with a fluorescent microscope, respectively. Chlorination reduced the culturability of Leg. pneumophila by 2.93-4.59 log CFU ml(-1) and damaged cellular membrane by 53.8-99.2%. Moreover, cells released from H. vermiformis exhibited significantly lower degrees in culturability reduction (P = 0.0008) and membrane deterioration (P < 0.0001) when compared with those from A. castellanii. The amoebic genus is the most significant parameter affecting cytoplasmic membrane integrity of chlorinated Legionella (P < 0.0001), followed by free chlorine concentration (P = 0.042). CONCLUSIONS: Legionella pneumophila replicated from H. vermiformis possess greater chlorine resistance than the cells from A. castellanii. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the heterogeneity of amoebae-grown Leg. pneumophila in chlorine susceptibility, which should be considered in the control of legionellae proliferation, particularly in the systems where H. vermiformis is dominant, e.g. hot water plumbing.
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