Growth of legionella and other heterotrophic bacteria in a circulating cooling water system exposed to ultraviolet irradiation

Kusnetsov, Jaana; Keskitalo, P.J.; Ahonen, H.E.; Tulkki, A.I.; Miettinen, Ilkka T.; Martikainen, Pertti J.

doi:10.1111/j.1365-2672.1994.tb03450.x

Cited by 23 publications

(13 citation statements)

References 22 publications

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“…However, evidence that UV irradiation alone has a significant effect on reducing microbial contamination is equivocal owing to the relative resistance of some important water-borne pathogenic species (Kusnetsov et al, 1994). This method would appear to be an attractive non-polluting alternative for point of entry of mains water purification.…”

Section: Biocides and Chemical Disinfectantsmentioning

confidence: 99%

Biofilm formation and control in dental unit waterlines

et al. 2005

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Section: Biocides and Chemical Disinfectantsmentioning

confidence: 99%

Biofilm formation and control in dental unit waterlines

et al. 2005

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“…Ultraviolet radiation has been proposed for disinfection of water in distribution systems (Liu et al, 1994b;. However, ultraviolet treatment is generally ineffective in controlling Legionella in cooling towers because of its growth within bio®lms (Kusnetsov et al, 1994b).…”

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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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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“…Following growth at 37°C in buffered yeast extract (BYE) broth to late log phase (56), wild types and mutants were inoculated into flasks containing 50 ml of the tap water, and then the cultures were incubated with shaking. As with other wild-type L. pneumophila (30,41,42,54,57), 130b persisted in low-temperature tap water for extended times (Fig. 1).…”

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Importance of Type II Secretion for Survival of Legionella pneumophila in Tap Water and in Amoebae at Low Temperatures

Söderberg

Dao

Starkenburg

et al. 2008

Appl Environ Microbiol

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Legionella pneumophila type II secretion mutants showed reduced survival in both tap water at 4 to 17°C and aquatic amoebae at 22 to 25°C. Wild-type supernatants stimulated the growth of these mutants, indicating that secreted factors promote low-temperature survival. There was a correlation between low-temperature survival and secretion function when 12 additional Legionella species were examined.Legionella pneumophila is widespread in natural and manmade water systems (8,21,29,39,41,47,53,64). In these habitats, L. pneumophila exists planktonically, within protozoa, and in biofilms (14,35,36,41,45). The ubiquity of L. pneumophila is also a result of the organism's ability to survive at many temperatures, including ones as low as 4°C (21,29,62,64). L. pneumophila is an important pathogen of humans, with the inhalation of contaminated water droplets originating from aerosol-generating devices resulting in Legionnaires' disease (16). Given the manner in which infection occurs, it is important to better understand how legionellae survive in water, in protozoa, and at low temperatures. Recently, we found that L. pneumophila type II protein secretion is critical for growth in rich broth or agar at 12 to 25°C but not in medium at 30 to 37°C (56). Operative in many gram-negatives (9), type II secretion is a multistep process in which proteins are translocated across the inner membrane in a Sec-or Tat-dependent manner, recognized in the periplasm, and then delivered to the T2S apparatus, whereupon a pilus-like structure "pushes" proteins through a dedicated outer membrane pore or secretin (28).To investigate the connection between type II secretion and low-temperature survival under conditions that more closely mimic natural habitats, we compared wild-type serogroup 1 strain 130b (Table 1) and its type II secretion mutants for persistence in tap water incubated at 37°C, 25°C, and 17°C. We used three mutants: NU258, containing a mutation in the genes encoding the type II outer membrane secretin (lspD) and the inner membrane ATPase (lspE); NU275, containing a mutation in the gene for the inner membrane platform protein (lspF); and NU272 mutated in the gene encoding the pseudopilin peptidase (pilD) (51). Tap water was obtained from laboratory sinks and filter sterilized. Following growth at 37°C in buffered yeast extract (BYE) broth to late log phase (56), wild types and mutants were inoculated into flasks containing 50 ml of the tap water, and then the cultures were incubated with shaking. As with other wild-type L. pneumophila (30,41,42,54,57), 130b persisted in low-temperature tap water for extended times (Fig. 1). Also similar to previous work (27), the recovery of CFU was maintained for a longer period at low temperatures below 37°C. But across the 17 to 37°C range, the secretion mutants behaved differently than their parent (Fig. 1). At 37°C, the mutants displayed a greater recoverability than 130b between days 7 and 20 (P Ͻ 0.05). In a similar vein, at 25°C, the mutants were recovered more than the wild type was be...

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Growth of legionella and other heterotrophic bacteria in a circulating cooling water system exposed to ultraviolet irradiation

Cited by 23 publications

References 22 publications

Biofilm formation and control in dental unit waterlines

Biofilm formation and control in dental unit waterlines

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

Importance of Type II Secretion for Survival of Legionella pneumophila in Tap Water and in Amoebae at Low Temperatures

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