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The role of amoeba in water

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The role of Amoeba in water systems

It is well known that amoeba support the intracellular growth and survival of pathogenic bacteria such as Legionella pneumophila and Pseudomonas species. In a paper by Kilvington et al (Investigative Ophthalmology & Visual Science, January 2004, Vol 45, No1) it was noted that 8 of 27 homes tested had Acanthamoeba present, with 89% of the homes showing free living amoeba present. They concluded water storage tanks promote colonisation of water by amoeba. Acantamoeba polyphaga A report by Thomas et al (Journal of Applied Microbiology 2004, 97, 950-963) described the use of various biocides in waters containing planktonic Legionella and biofilms. This concluded that chlorine dioxide, applied as a continuous treatment, was the most efficient for controlling Legionella pneumophila in domestic water systems. Other biocides tested were chlorine at 2.5mg/l, ozone at 0.5mg/l, monochloramine at 0.5mg/l and copper-silver ionisation at 0.8/0.02mg/l. Amoeba resisted all the treatments applied and probably acted as a reservoir for Legionella allowing a quick re-colonisation of the system once the treatments were interrupted. A further report by Francine Marciano-Cabral and Guy Cabral (Clinical Microbiology Reviews, 2003, p273-307) showed Polyhexamethylene biguanide (PHMB), manufactured as an environmental disinfectant known as Baquacil by Zeneca Pharmaceuticals, was shown to exhibit both amoebicidal and cysticidal activity against a number of Acanthamoeba strains. This report further said: The role of Acanthamoeba spp. as reservoirs or vectors for human pathogens has been examined. Rowbotham studied the interaction of Acanthamoeba with Legionella pneumophila, the causative agent of atypical pneumonia in humans. Several strains of L. pneumophila, normally intracellular pathogens of alveolar macrophages, were found to infect Acanthamoeba, indicating that free-living amoebae could serve as natural hosts of Legionella. Following phagocytosis by Acanthamoeba, Legionella organisms were observed to “escape” into the cytoplasm rather than being sequestered into lysosomal structures and being degraded by hydrolytic enzymes. Following multiplication, the Legionella organisms lysed the amoebae and were released into the surrounding environment. Based on these observations, Rowbotham suggested that vesicles filled with Legionella or amoebae filled with bacteria, rather than free bacteria, were the source of legionellosis. Consistent with the postulate of an interaction between Acanthamoeba and Legionella is the observation that Legionella and amoebae have been isolated from the same aquatic environments Indeed, amoebae isolated directly from river water or soil have been shown to contain Legionella spp. Studies have demonstrated that the temperature at which Legionella and the amoebae interact is important. Legionella-induced lysis of host Acanthamoeba cells has been observed to occur at an ambient temperature of 37°C. However, at lower temperatures such as 20°C, a converse interaction occurs in that the amoebae phagocytize and digest Legionella. Since the initial observations of Rowbotham, the interaction of Legionella with free-living amoebae has been widely studied. Uptake of Legionella can occur through “coiling” phagocytosis. Bozue and Johnson indicated that following uptake, inhibition of lysosomal fusion with phagosomes containing Legionella occurs within A. castellanii. Subsequently, intracellular multiplication of Legionella and killing of host macrophages and amoebae have been described. However, while Legionella induces apoptotic cell death in macrophages, it reportedly does not do so in A. castellanii. Gao and Kwaik using L. pneumophila and A.polyphaga, confirmed that L. pneumophila does not kill amoebae by apoptosis but, rather, does so by necrosis. Necrotic cell death induced by L. pneumophila and subsequent release of these bacteria from the amoebae apparently is mediated by the pore-forming activity of the bacteria. Mutants defective in pore-forming activity fail to exit Acanthamoeba. Hartmannella vermiformis (orange) as it entraps a Legionella pneumophila bacterium (green) The mechanisms for recognition, entry, and intracellular proliferation of bacteria in amoebae and in mammalian cells may be similar. Adaptation of such bacteria to both mammalian cells and amoebae suggests an interaction which may confer specified functional attributes to the bacteria. Survival and intracellular growth of bacteria in amoebae may prime bacteria for intracellular growth in mammalian cells Cirillo et al. suggested that survival of Legionella strains from intracellular digestion in Acanthamoeba pre-adapted the bacteria for invasion of human and animal host cells. Recent studies have shown that the interaction of bacteria with amoebae may result in changes in the morphology and physiology of the bacteria. For example, L. pneumophila cells grown in Acanthamoeba were reported to be smaller than when cultured in vitro, to display different surface properties, and to exhibit enhanced motility. In addition, de novo synthesis of select L. pneumophila antigens has been demonstrated in bacteria grown in amoebae. Also, bacteria grown in amoebae are resistant to chemical disinfectants, and vesicles containing Legionella released from amoebae are highly resistant to biocides. Furthermore, it has been reported that growth in A. castellanii enhances the capacity of Legionella to invade macrophages and increases the intracellular replication of the bacteria. Mycobacterium avium grown in Acanthamoeba also demonstrated enhanced entry and intracellular replication in macrophages. The interaction of Legionella with free-living amoebae raises intriguing possibilities for a functional relevance regarding human disease. For example, Legionella-like amoeba pathogens (LLAP) which may represent a source of respiratory disease in humans have been identified.

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© 2016-2019 Collaton Consultancy Limited, 8 Grampian Close,

Collaton St Mary, Paignton Devon, TQ4 7GD, United Kingdom. UK

Company Registration number 9930189

Site Map

The role of amoeba in water

Knowledge

The role of Amoeba in water systems

It is well known that amoeba support the intracellular growth and survival of pathogenic bacteria such as Legionella pneumophila and Pseudomonas species. In a paper by Kilvington et al (Investigative Ophthalmology & Visual Science, January 2004, Vol 45, No1) it was noted that 8 of 27 homes tested had Acanthamoeba present, with 89% of the homes showing free living amoeba present. They concluded water storage tanks promote colonisation of water by amoeba. Acantamoeba polyphaga A report by Thomas et al (Journal of Applied Microbiology 2004, 97, 950- 963) described the use of various biocides in waters containing planktonic Legionella and biofilms. This concluded that chlorine dioxide, applied as a continuous treatment, was the most efficient for controlling Legionella pneumophila in domestic water systems. Other biocides tested were chlorine at 2.5mg/l, ozone at 0.5mg/l, monochloramine at 0.5mg/l and copper-silver ionisation at 0.8/0.02mg/l. Amoeba resisted all the treatments applied and probably acted as a reservoir for Legionella allowing a quick re-colonisation of the system once the treatments were interrupted. A further report by Francine Marciano-Cabral and Guy Cabral (Clinical Microbiology Reviews, 2003, p273-307) showed Polyhexamethylene biguanide (PHMB), manufactured as an environmental disinfectant known as Baquacil by Zeneca Pharmaceuticals, was shown to exhibit both amoebicidal and cysticidal activity against a number of Acanthamoeba strains. This report further said: The role of Acanthamoeba spp. as reservoirs or vectors for human pathogens has been examined. Rowbotham studied the interaction of Acanthamoeba with Legionella pneumophila, the causative agent of atypical pneumonia in humans. Several strains of L. pneumophila, normally intracellular pathogens of alveolar macrophages, were found to infect Acanthamoeba, indicating that free-living amoebae could serve as natural hosts of Legionella. Following phagocytosis by Acanthamoeba, Legionella organisms were observed to “escape” into the cytoplasm rather than being sequestered into lysosomal structures and being degraded by hydrolytic enzymes. Following multiplication, the Legionella organisms lysed the amoebae and were released into the surrounding environment. Based on these observations, Rowbotham suggested that vesicles filled with Legionella or amoebae filled with bacteria, rather than free bacteria, were the source of legionellosis. Consistent with the postulate of an interaction between Acanthamoeba and Legionella is the observation that Legionella and amoebae have been isolated from the same aquatic environments Indeed, amoebae isolated directly from river water or soil have been shown to contain Legionella spp. Studies have demonstrated that the temperature at which Legionella and the amoebae interact is important. Legionella-induced lysis of host Acanthamoeba cells has been observed to occur at an ambient temperature of 37°C. However, at lower temperatures such as 20°C, a converse interaction occurs in that the amoebae phagocytize and digest Legionella. Since the initial observations of Rowbotham, the interaction of Legionella with free-living amoebae has been widely studied. Uptake of Legionella can occur through “coiling” phagocytosis. Bozue and Johnson indicated that following uptake, inhibition of lysosomal fusion with phagosomes containing Legionella occurs within A. castellanii. Subsequently, intracellular multiplication of Legionella and killing of host macrophages and amoebae have been described. However, while Legionella induces apoptotic cell death in macrophages, it reportedly does not do so in A. castellanii. Gao and Kwaik using L. pneumophila and A.polyphaga, confirmed that L. pneumophila does not kill amoebae by apoptosis but, rather, does so by necrosis. Necrotic cell death induced by L. pneumophila and subsequent release of these bacteria from the amoebae apparently is mediated by the pore-forming activity of the bacteria. Mutants defective in pore-forming activity fail to exit Acanthamoeba. Hartmannella vermiformis (orange) as it entraps a Legionella pneumophila bacterium (green) The mechanisms for recognition, entry, and intracellular proliferation of bacteria in amoebae and in mammalian cells may be similar. Adaptation of such bacteria to both mammalian cells and amoebae suggests an interaction which may confer specified functional attributes to the bacteria. Survival and intracellular growth of bacteria in amoebae may prime bacteria for intracellular growth in mammalian cells Cirillo et al. suggested that survival of Legionella strains from intracellular digestion in Acanthamoeba pre-adapted the bacteria for invasion of human and animal host cells. Recent studies have shown that the interaction of bacteria with amoebae may result in changes in the morphology and physiology of the bacteria. For example, L. pneumophila cells grown in Acanthamoeba were reported to be smaller than when cultured in vitro, to display different surface properties, and to exhibit enhanced motility. In addition, de novo synthesis of select L. pneumophila antigens has been demonstrated in bacteria grown in amoebae. Also, bacteria grown in amoebae are resistant to chemical disinfectants, and vesicles containing Legionella released from amoebae are highly resistant to biocides. Furthermore, it has been reported that growth in A. castellanii enhances the capacity of Legionella to invade macrophages and increases the intracellular replication of the bacteria. Mycobacterium avium grown in Acanthamoeba also demonstrated enhanced entry and intracellular replication in macrophages. The interaction of Legionella with free-living amoebae raises intriguing possibilities for a functional relevance regarding human disease. For example, Legionella-like amoeba pathogens (LLAP) which may represent a source of respiratory disease in humans have been identified.

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