Survival of virulent<i>Legionella pneumophila</i>in aerosols

Hambleton, Peter; Broster, M. G.; Dennis, P. J.; Henstridge, R. M.; Fitzgeorge, R. B.; Conlan, J. Wayne

doi:10.1017/s0022172400029090

Cited by 69 publications

(45 citation statements)

References 49 publications

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“…Furthermore, post-exponential-phase cultures of L. pneumophila express a number of traits that have been correlated with virulence (3). Hambleton et al (6) reported that L. pneumophila cell populations in the exponential phase survived poorly in aerosols with a humidity of 65% compared to postexponential-phase cells. Interestingly, in comparisons of the exponential and post-exponential phases, cultivability loss occurred faster in the post-exponential phase with an inoculum size of 10 6 CFU ml Ϫ1 , whereas the converse was found at 10 8 CFU ml Ϫ1 .…”

Section: Discussionmentioning

confidence: 99%

Factors Influencing Survival of Legionella pneumophila Serotype 1 in Hot Spring Water and Tap Water

Ohno¹,

Kato

Yamada

et al. 2003

Appl Environ Microbiol

108

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The factors involved in the survival of Legionella pneumophila in the microcosms of both hot spring water and tap water were studied by examining cultivability and metabolic activity. L. pneumophila could survive by maintaining metabolic activity but was noncultivable in all microcosms at 42°C, except for one microcosm with a pH of <2.0. Lower temperatures supported survival without loss of cultivability. The cultivability declined with increasing temperature, although metabolic activity was observed at temperatures of up to 45°C. The optimal range of pH for survival was between 6.0 and 8. The metabolic activity could be maintained for long periods even in microcosms with high concentrations of salt. The cultivability of organisms in the postexponential phase in a tap water microcosm with a low inoculum size was more rapidly reduced than that of organisms in the exponential phase. In contrast, the loss of cultivability in microcosms of a high inoculum size was significant in the exponential phase. Random(ly) amplified polymorphic DNA analysis of microcosms where cultivability was lost but metabolic activity was retained showed no change compared to cells grown freshly, although an effect on the amplified DNA band pattern by production of stress proteins was expected.Resuscitation by the addition of Acanthamoeba castellanii to the microcosm in which cultivability was completely lost but metabolic activity was maintained was observed only in part of the cell population. Our results suggest that L. pneumophila cell populations can potentially survive as free organisms for long periods by maintaining metabolic activity but temporarily losing cultivability under strict environments and requiring resuscitation by ingestion by amoebas.Legionella pneumophila, the organism that causes Legionnaires' disease and Pontiac fever, is a ubiquitous bacterium in natural or man-made aqueous environments and requires an intracellular environment of free-living amoebas for its replication (19). However, this pathogen is also known to survive as a free organism for long periods in low-nutrient environments under appropriate conditions (14, 15). Bacterial populations released in an aqueous environment are frequently exposed to stresses due to limitations and changes in nutrient availability, temperature, salinity, oxygen, and pH. To adapt to such a stressful environment, bacteria often enter a "temporarily noncultivable state," in which they regulate cell differentiation to adapt to such stresses and then resuscitate when environmental conditions become favorable for growth. This physical change is generally referred to as "viable but noncultivable," and some bacteria use this strategy (12). L. pneumophila cell populations that entered a noncultivable state in tap water were also reportedly resuscitated by injection into embryonated eggs (9) or by passage through Acanthamoeba castellanii (18).Japan is an eminently volcanic country, and hot springs are widespread. Japanese people enjoy a culture of bathing in hot springs, and recently ...

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Section: Discussionmentioning

confidence: 99%

Factors Influencing Survival of Legionella pneumophila Serotype 1 in Hot Spring Water and Tap Water

Ohno¹,

Kato

Yamada

et al. 2003

Appl Environ Microbiol

108

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“…pneumophila serogroup 1 (74/81) (Hambleton et al, 1983). This strain was isolated from a naturally contaminated water supply and had been subcultured on artificial media a maximum of three times.…”

Section: G M Schofield a N D A E W R I G H Tmentioning

confidence: 99%

Survial of Legionella pneumophila in a Model Hot Water Distribution System

Schofield¹,

Wright²

1984

Microbiology

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A virulent strain of Legionella pneumophila was inoculated into an enclosed system supplied with unsterilized water from a domestic hot water supply. Growth of bacteria was monitored over 10 weeks. An increase in the number of organisms other than legionellas occurred but few amoebae were observed and none could be cultured. Viable counts of L. pneumophila in the circulation fluid decreased slightly. However, particles of debris which accumulated in the apparatus and which were stained by the indirect fluorescent antibody technique were found to be almost totally composed of L. pneumophila. On dismantling the apparatus Legionella was isolated in moderately high numbers from several different types of surfaces, particularly natural rubber and silicone.

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“…The number of Legionnaires' disease patients reaches a peak in the summer season in Japan because of the high temperature and high relative humidity (NIID, 2008), which have been associated with cases of legionellosis (Fisman et al, 2005). The survival of L. pneumophila is greatest under >65% relative humidity conditions (Berendt, 1980;Hambleton et al, 1983;Dennis & Lee, 1988). According to the APHC, no Legionnaires' disease patients were found in the Adachi outbreak area.…”

Section: Estimated Exposure Dose and Risk In The Adachi Outbreak Areamentioning

confidence: 99%

Assessing the risk of Legionnaires’ disease: The inhalation exposure model and the estimated risk in residential bathrooms

Azuma

Uchiyama

Okumura

2013

Regulatory Toxicology and Pharmacology

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Survival of virulentLegionella pneumophilain aerosols

Cited by 69 publications

References 49 publications

Factors Influencing Survival of Legionella pneumophila Serotype 1 in Hot Spring Water and Tap Water

Factors Influencing Survival of Legionella pneumophila Serotype 1 in Hot Spring Water and Tap Water

Survial of Legionella pneumophila in a Model Hot Water Distribution System

Assessing the risk of Legionnaires’ disease: The inhalation exposure model and the estimated risk in residential bathrooms

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