Impact of Chlorine and Heat on the Survival of
            <i>Hartmannella vermiformis</i>
            and Subsequent Growth of
            <i>Legionella pneumophila</i>

Studies on Legionella show a continuum from environment to human disease. Legionellosis is caused by Legionella species acquired from environmental sources, principally water sources such as cooling towers, where Legionella grows intracellularly in protozoa within biofilms. Aquatic biofilms, which are widespread not only in nature, but also in medical and dental devices, are ecological niches in which Legionella survives and proliferates and the ultimate sources to which outbreaks of legionellosis can be traced. Invasion and intracellular replication of L. pneumophila within protozoa in the environment play a major role in the transmission of Legionnaires' disease. Protozoa provide the habitats for the environmental survival and reproduction of Legionella species. L. pneumophila proliferates intracellularly in various species of protozoa within vacuoles studded with ribosomes, as it also does within macrophages. Growth within protozoa enhances the environmental survival capability and the pathogenicity (virulence) of Legionella. The growth requirements of Legionella, the ability of Legionella to enter a viable non‐culturable state, the association of Legionella with protozoa and the occurrence of Legionella within biofilms complicates the detection of Legionella and epidemiological investigations of legionellosis. Polymerase chain reaction (PCR) methods have been developed for the molecular detection of Legionella and used in environmental and epidemiological studies. Various physical and chemical disinfection methods have been developed to eliminate Legionella from environmental sources, but gaining control of Legionella in environmental waters, where they are protected from disinfection by growing within protozoa and biofilms, remains a challenge, and one that must be overcome in order to eliminate sporadic outbreaks of legionellosis.

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“…Legionella are relatively resistant to conventional chlorination (Kuchta et al, 1993). Legionella spp.…”

Section: Detection and Disinfectionmentioning

confidence: 99%

Legionella: from environmental habitats to disease pathology, detection and control

Atlas

1999

Environmental Microbiology

213

148

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“…Hartmannella vermiformis was more resistant to chlorine than any of the Candida spp. tested certainly due to its ability to form cysts with a double wall (Kuchta et al, 1993;Greub & Raoult, 2004). Chlorine doses of 3 and 6 lg mL À1 had no effect, compared with control ('0 lg mL À1 ', hatched).…”

Section: Chlorine Treatmentmentioning

confidence: 99%

“…Microscopic observations showed that amoebae resistant to H 2 O 2 at 9000 lg mL À1 were in cyst form (data not shown). Cysts are well known to be less vulnerable than trophozoites (Kuchta et al, 1993;Greub & Raoult, 2004).…”

Section: Hydrogen Peroxide Treatmentmentioning

confidence: 99%

“…These results highlighted the negative influence of amoebae on the anti-Candida activity of Oxygenal 6©. FLA, which represent a form of protection against disinfectants for internalized microorganisms, may furthermore increase the virulence of microorganisms and amoebae, as is well known, for example, in the case of Legionella pneumophila (Kuchta et al, 1993;Greub & Raoult, 2004).…”

Section: Oxygenal 6© Treatmentmentioning

confidence: 99%

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Efficacy of dental unit disinfectants againstCandidaspp. andHartmannella vermiformis

et al. 2014

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Human oral commensal Candida yeasts, as well as environmental free-living amoebae (FLA) such as Hartmannella, are known to be direct or indirect human pathogens. These microorganisms may be isolated from dental unit waterlines (DUWL), because of contamination coming from the tap water and/or a patient's mouth. This study compared the efficacy of commonly used DUWL disinfectants (chlorine, H2 O2 , and Oxygenal 6©) against three species of Candida (C. albicans, C. glabrata, and C. parapsilosis) and one FLA species (H. vermiformis), growing either as single or as mixed biofilms in tap water. Results showed variable efficacies: H2 O2 had no significant activity, while chlorine was effective but only at the highest doses tested, probably not compatible with DUWL uses. Oxygenal 6© was the most efficacious in preventing the growth of yeasts in tap water. However, in the presence of FLA, Oxygenal 6© displayed a reduced antimicrobial activity against sessile C. albicans. In conclusion, none of the tested disinfectants could eradicate yeasts or FLA. Moreover, the antiyeast activity of Oxygenal 6© was reduced in the presence of FLA. Both sessile or planktonic and mixed or single-species conditions should be considered when evaluating the activity of disinfectants for DUWL maintenance. This study also highlighted that FLA should be included in the testing protocols.

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“…Trophozoites and cysts of Hartmannella vermiformis may survive at 4 mg l )1 of chlorine treatment and still support intracellular multiplication and growth of Leg. pneumophila (Kuchta et al 1993). Similarly, cysts of Acanthamoeba castellanii and Acanthamoeba polyphaga can retain their viability at 10 mg l )1 of chlorination (Kilvington and Price 1990;Storey et al 2004).…”

Section: Introductionmentioning

confidence: 97%

Heterogeneity in chlorine susceptibility forLegionella pneumophilareleased fromAcanthamoebaandHartmannella

Chang

Kao

Liu

2009

Journal of Applied Microbiology

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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 BCYEα 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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Impact of Chlorine and Heat on the Survival of Hartmannella vermiformis and Subsequent Growth of Legionella pneumophila

Cited by 75 publications

References 17 publications

Legionella: from environmental habitats to disease pathology, detection and control

Legionella: from environmental habitats to disease pathology, detection and control

Efficacy of dental unit disinfectants againstCandidaspp. andHartmannella vermiformis

Heterogeneity in chlorine susceptibility forLegionella pneumophilareleased fromAcanthamoebaandHartmannella

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