Pathogenic waterborne free-living amoebae: An update from selected Southeast Asian countries

Abstract

Data on the distribution of free-living amoebae is still lacking especially in Southeast Asian region. The aquatic environment revealed a high occurrence of free-living amoebae (FLA) due to its suitable condition and availability of food source, which subsequently causes infection to humans. A total of 94 water samples consisted of both treated and untreated from Laos (31), Myanmar (42), and Singapore (21) were investigated for the presence of pathogenic FLA. Each water sample was filtered and cultured onto non-nutrient agar seeded with live suspension of Escherichia coli and incubated at room temperature. Morphological identification was conducted for both trophozoites and cysts via microscopic stains (Giemsa and immunofluorescence). The presence of Naegleria-like structures was the most frequently encountered in both treated and untreated water samples, followed by Acanthamoeba-like and Vermamoeba-like features. To identify the pathogenic isolates, species-specific primer sets were applied for molecular identification of Acanthamoeba, Naegleria, and Vermamoeba. The pathogenic species of Acanthamoeba lenticulata and A. triangularis were detected from untreated water samples, while Vermamoeba vermiformis was found in both treated and untreated water samples. Our results suggested that poor water quality as well as inadequate maintenance and treatment might be the cause of this alarming problem since chlorine disinfection is ineffective in eradicating these amoebas in treated water samples. Regular monitoring and examination of water qualities are necessary in order to control the growth, hence, further preventing the widespread of FLA infections among the public.

Isolation and Molecular Identification of Acanthamoeba and Naegleria from Agricultural Water Canal in Qazvin, Iran

“…Our knowledge on the FLAs and the risk of human infections are still disputed. The geoecological distributions of such amoebas and their putative genotypes have been interesting fields of study during recent years ( 24 – 26 , 21 ). Herein, we have evaluated the frequency and genotypes of Acanthamoeba and Naegleria spp.…”

“…To isolate FLA, water samples were passed through a nitrocellulose filter membrane (pore size: 0.45 μm) using a vacuum pump; so that the amoeba remained on the filter surface and not going through the sieve. Then, filters were inversely placed on the surface of 1.5% non-nutrient agar (NNA) plate seeded with Escherichia coli bacteria and incubated at 25–30 °C ( 16 , 21 ). Cultures were followed up, up to 21 days in order to find trophozoites and/or cysts of the amoeba.…”

Acanthamoeba in Southeast Asia – Overview and Challenges

“…They have been isolated in untreated natural freshwaters, like lakes, ponds, hot springs and waterfalls [14–17]; and brackish, seawaters, and ocean sediments [18]. They were also isolated from treated waters like domestic water systems, swimming pools, hydrotherapy pools, remedial spas, tap water and drinking water [14,16,19,20]. Unconventional water sources like sewage and aquaria were not spared with the presence of amoebas [18].…”

“…Thus, individuals who are not contact lens wearers but have been constantly exposed to dust particles and soil are also at high risk of infection [25]. It is also important to note that exposure to Acanthamoeba can be as simple as accidental splash of contaminated water to the face or bruised skin [14], making a fast and easy transmission.…”

Notes from the Field: Acanthamoeba Keratitis Cases — Iowa, 2002–2017

“…AK is a sight-threatening condition, and outbreaks have been linked to specific contact lens solutions ( 3 ), hard water with lime scale ( 4 ), and biofilm contamination of domestic and recreational water ( 5 , 6 ). The expanding problem of algal bloom and nutrient pollution in Iowa waters might also be contributing to an increase in pathogenic Acanthamoeba species and the rising number of AK cases ( 6 ). Although this investigation was limited by its retrospective design and analysis of data obtained from a single center, UIHC is likely to evaluate most AK cases in Iowa.…”