Isolation and identification of Acanthamoeba genotypes and Naegleria spp. from the water samples of public swimming pools in Qazvin, Iran

Free-living amoeba (FLA), including Acanthamoeba and Naegleria are facultative parasites in humans. The amoeba have widespread distribution in various water sources. The aim of this study was isolation and molecular identification of Acanthamoeba and Naegleria isolated from swimming pools and also hot and cold tub waters in Qazvin province. The samples (166 water samples) were cultured to isolate and identify positive specimens. PCR (polymerase chain reaction) amplification, sequencing and phylogenetic analysis were conducted to confirm the isolated species and genotypes of amoeba. According to morphological characterizations, 18.6% of specimens were identified as FLA, which in 71% were Acanthamoeba by PCR method. Molecular analysis revealed that 36.3%, 18.1% and 4.5% of Acanthamoeba specimens were identified as T3, T4 and T11 Acanthamoeba genotypes, respectively. Protacanthamoeba bohemica (27.2%) and Acanthamoeba sp. (4.5%) were found among the specimens. The results of osmo-tolerance and thermo-tolerance assays demonstrated that 50% of T3 and 25% of T4 genotypes of Acanthamoeba were highly pathogenic parasites. The molecular approach showed the presence of Naegleria lovaniensis (9%) in hot tub water of swimming pools. This study demonstrated that the swimming pools and hot tub water in Qazvin province were contaminated with Acanthamoeba and Naegleria species.

Isolation and molecular characterization of a Naegleria strain from a recreational water fountain in Tenerife, Canary Islands, Spain

Free-Living Amoebae (FLA) are widely distributed protozoa in the environment and have been isolated from many sources such as dust, soil and water. Among the pathogenic genera included in this group Acanthamoeba spp., Naegleria fowleri and Balamuthia mandrillaris have been reported to be causative agents of lethal encephalitis, disseminated infections and keratitis. Naegleria fowleri is a pathogenic FLA species which causes Primary Amoebic Meningoencephalitis (PAM). At present there are not many available data on the distribution of Naegleria species in Spain from environmental sources. Therefore, the aim of this study was to evaluate the presence of this genus in recreational water sources in the island of Tenerife, Canary Islands, Spain. In this study, ten samples collected from recreational water fountains were checked for the presence of Naegleria spp. using morphological and molecular identification tools. From the analysed samples, only one sample (seawater fountain) was positive for Naegleria spp. interestingly, not many reports of Naegleria spp. in seawater are available in the literature and thus awareness should be raised among the environmental and public health professionals.

Occurrence of Naegleria species in therapeutic geothermal water sources, Northern Iran

Potentially pathogenic Free-Living Amoebae include members belonging to Naegleria genus. The species N. fowleri is known worldwide as the causative agent of the lethal Primary Amoebic Meningoencephalitis (PAM). Only one clinical case of N. fowleri has been reported in Iran. Several species of Naegleria have been reported to be natural carriers of other potentially pathogenic microbial agents. The thermotolerance properties of this genus facilitates their presence in geothermal water sources including hot springs and spas. In the current study water samples were collected from 22 therapeutic hot springs, Northern Iran and investigated for the presence of Naegleria spp. using morphological keys and PCR/DNA sequencing based methods. Incubation of collected samples were done at both 30°C and 45°C in order to detect Naegleria spp. and N. fowleri, respectively. Thermotolerance assay and flagellation tests were also performed. The obtained results revealed that 54% of the investigated water samples were positive for Naegleria spp. including N. australiensis, N. americana, N. dobsoni, N. pagei, N. polaris and N. fultoni. The pathogenic N. fowleri was not detected. The most detected Naegleria was belonged to N. australiensis. This is the first report on the Naegleria spp. occurrence in hot springs in Northern Iran showing that most of the surveyed hot spring sources were contaminated with non-pathogenic Naegleria spp. However, due to the recent report of PAM in the country, further studies to investigate the presence of pathogenic N. fowleri in the environment and clinical samples is needed in the region and worldwide.

Differential Legionella spp. survival between intracellular and extracellular forms in thermal spring environments

Legionella are commonly found in natural and man-made aquatic environments and are able to inhabit various species of protozoa. The relationship between the occurrence of Legionella spp. within protozoa and human legionellosis has been demonstrated; however, the proportions of intracellular and extracellular Legionella spp. in the aquatic environment were rarely reported. In this study, we developed a new method to differentiate intracellular and extracellular Legionella spp. in the aquatic environment. Water samples from three thermal spring recreational areas in southeastern Taiwan were collected and analyzed. For each water sample, concurrent measurements were performed for Legionella spp. and their free-living amoebae hosts. The overall detection rate was 32 % (16/50) for intracellular Legionella spp. and 12 % (6/50) for extracellular Legionella spp. The most prevalent host of Legionella spp. was Hartmannella vermiformis. The identified Legionella spp. differed substantially between intracellular and extracellular forms. The results showed that it may be necessary to differentiate intracellular and extracellular forms of Legionella spp.

Youngest survivor of naegleria meningitis

Primary amebic meningoencephalitis (PAME) is a rare condition, usually caused by free living motile amebae. These are universally fatal infections with very few survivors reported till now. The authors report a 25-d-old boy, the youngest survivor of Naegleria meningitis. The child was admitted with a diagnosis of partially treated meningitis. Cerebro-spinal fluid wet mount examination revealed free living motile amebae resembling Naegleria, which was further confirmed by culture. He was treated with amphoterecin B, rifampicin and fluconazole for 4 wk and ventriculoperitoneal shunt for obstructive hydrocephalous. At 8 mo follow up, child has survived with neurological sequlae.

Screening of recreational areas of rivers for potentially pathogenic free-living amoebae in the suburbs of Tehran, Iran

A survey was conducted to determine the presence of free-living amoebae (FLA), especially Acanthamoeba and Naegleria, in river recreation areas in Tehran Province, Iran. All rivers surveyed were associated with human activity, and two were also a source of municipal tap water. Fifty-five water samples from 10 major rivers were screened for FLA and identified by morphological characters, PCR amplification targeting specific genes for Acanthamoeba (DF3 region of Rns gene) and other FLA (ITS PCR), and homology analysis. The percentage of positive FLA isolates was 27.3%, of which 80% were Acanthamoeba, assigned to the T4 and T15 genotype, and 20% were Naegleria. Isolation of Acanthamoeba T4 genotype (91.7%) from recreation areas could be a health threat and a sanitary risk associated with human activity where young people and tourists congregate in summer. Posting of warning signs and education of high-risk individuals are important for disease prevention. To the best of our knowledge this is the first report of genotype T15 (clustered with A. jacobsi) identified in Iran and the first report of the distribution of FLA such as Naegleria (N. pagei, N. clarki and N. fultoni) in recreation areas in rivers of Tehran Province using molecular methods.

Detection of Naegleria species in environmental samples from Peninsular Malaysia

BACKGROUND

In Malaysia, researchers and medical practitioners are unfamiliar with Naegleria infections. Thus little is known about the existence of pathogenic Naegleria fowleri, and the resultant primary amoebic meningoencephalitis (PAM) is seldom included in the differential diagnosis of central nervous system infections. This study was conducted to detect the presence of Naegleria species in various environmental samples.

METHODS/FINDINGS

A total of 41 Naegleria-like isolates were isolated from water and dust samples. All these isolates were subjected to PCR using two primer sets designed from the ITS1-ITS2 regions. The N. fowleri species-specific primer set failed to produce the expected amplicon. The Naegleria genus-specific primers produced amplicons of 408 bp (35), 450 bp (2), 457 bp (2) or 381 bp (2) from all 41 isolates isolated from aquatic (33) and dust (8) samples. Analysis of the sequences from 10 representative isolates revealed that amplicons with fragments 408, 450 and 457 bp showed homology with non-pathogenic Naegleria species, and 381 bp showed homology with Vahlkampfia species. These results concurred with the morphological observation that all 39 isolates which exhibited flagella were Naegleria, while 2 isolates (AC7, JN034055 and AC8, JN034056) that did not exhibit flagella were Vahlkampfia species.

CONCLUSION

To date, pathogenic species of N. fowleri have not been isolated from Malaysia. All 39 isolates that produced amplicons (408, 450 and 457 bp) from the genus-specific primers were identified as being similar to nonpathogenic Naegleria. Amplicon 408 bp from 5 representative isolates showed 100% and 99.7% identity to Naegleria philippinensis isolate RJTM (AM167890) and is thus believed to be the most common species in our environment. Amplicons 450 bp and 457 bp were respectively believed to be from 2 new species of Naegleria, since representative isolates showed lower homology and had a longer base pair length when compared to the reference species in the Genbank, Naegleria schusteri (AJ566626) and Naegleria laresi (AJ566630), respectively.

Detection of free living amoebae, Acanthamoeba and Naegleria, in swimming pools, Malaysia

This study reports the detection of Acanthamoeba and Naegleria species in 14 swimming pools around Petaling Jaya and Kuala Lumpur, Malaysia. Sampling was carried out at 4 sites (the platforms (P), wall (W), 1 meter from the wall (1) and middle (2)) of each swimming pool. These free living amoebae (FLA) were detected under light and inverted microscopes after being cultured on the surface of non-nutrient agar lawned with Escherichia coli. Acanthamoeba species were detected in higher number of culture plates from all sampling sites of all the swimming pools. While Naegleria, were detected in fewer culture plates at 3 sampling sites (absent at site P) of 8 swimming pools. This suggested that the thick double-walled cysts of Acanthamoeba were more resistant, thus remaining viable in the dry-hot areas of the platforms and in chlorinated water of the swimming pools whereas Naegleria cysts, that are fragile and susceptible to desiccation, preferred watery or moist areas for growth and proliferation. The prevalence of both FLA was highest at site W (76.2%), followed by site 1 (64.7%), lowest at site 2 (19.4%), and could be detected at all 3 sampling levels (top, middle and bottom) of these 3 sites. The surface of site W might act as a bio-film that accumulated all kinds of microbes providing sufficient requirement for the FLA to develop and undergo many rounds of life cycles as well as moving from top to bottom in order to graze food. Other factors such as human activities, the circulating system which was fixed at all swimming pools, blowing wind which might carry the cysts from surroundings and the swimming flagellate stage of Naegleria could also contribute to the distribution of the FLA at these sampling sites. Both FLA showed highest growth (80.4%) at room temperature (25-28 ºC) and lesser (70.0%) at 37 ºC which might be due to the overgrowth of other microbes (E. coli, fungi, algae, etc). While at 44 ºC, only Acanthamoeba species could survive thus showing that our swimming pools are free from potentially pathogenic Naegleria species. However, further study is needed in order to confirm the virulence levels of these amoebae isolates.

Primary Amoebic Meningoencephalitis in a Patient with Systemic Lupus Erythematosus

This report describes a case of primary amoebic meningoencephalitis in a patient with systemic lupus erythematosus. No specific exposure was identified. Treatment with intravenous amphotericin B was associated with marked clinical improvement, but subsequent fatal relapse while still on therapy.

Survey of pathogenic free-living amoebae and Legionella spp. in mud spring recreation area

Acanthamoeba, Hartmannella, and Naegleria are free-living amoebae, ubiquitous in aquatic environments. Several species within these genera are recognized as potential human pathogens. These free-living amoebae may facilitate the proliferation of their parasitical bacteria, such as Legionella. In this study, we identified Acanthamoeba, Hartmannella, Naegleria, and Legionella using various analytical procedures and investigated their occurrence at a mud spring recreation area in Taiwan. We investigated factors potentially associated with the prevalence of the pathogens, including various water types, and physical and microbiological water quality parameters. Spring water was collected from 34 sites and Acanthamoeba, Hartmannella, Naegleria, and Legionella were detected in 8.8%, 35.3%, 14.7%, and 47.1%, respectively. The identified species of Acanthamoeba included Acanthamoeba castellanii and Acanthamoeba polyphaga. Nearly all the Hartmannella isolates are identified as Hartmannella vermiformis. The Naegleria species included Naegleria australiensis and its sister groups, and two other isolates referred to a new clade of Naegleria genotypes. The Legionella species identified included unnamed Legionella genotypes, Legionella pneumophila serotype 6, uncultured Legionella spp., Legionella lytica, Legionella drancourtii, and Legionella waltersii. Significant differences (Mann-Whitney U test, P<0.05) were observed between the presence/absence of Hartmannella and total coliforms, between the presence/absence of Naegleria and heterotrophic plate counts, and between the presence/absence of Legionella and heterotrophic plate counts. This survey confirms that pathogenic free-living amoebae and Legionella are prevalent in this Taiwanese mud spring recreation area. The presence of pathogens should be considered a potential health threat when associated with human activities in spring water.

Differential Salmonella survival against communities of intestinal amoebae

Predation from intestinal amoebae may provide selective pressure for the maintenance of high genetic diversity at the Salmonella enterica rfb locus, whereby serovars better escape predators in particular environments depending on the O-antigens they express. Here, the hypothesis that amoebae from a particular intestinal environment collectively prefer one serovar over another is tested. Collections of Acanthamoeba, Tetramitus, Naegleria and Hartmannella were isolated from the intestinal tracts of several vertebrate hosts, including bullfrog tadpoles, goldfish, turtles and bearded dragons, and their feeding preferences were determined. Congeneric amoebae from the same environment had significantly similar feeding preferences. Strikingly, even unrelated amoebae - such as Naegleria and Tetramitus from goldfish - also had significantly similar feeding preferences. Yet amoebae isolated from different environments showed no similarity in prey choice. Thus, feeding preferences of amoebae appear to reflect their environment, not their taxonomic relationships. A mechanism mediating this phenotypic convergence is discussed.

High throughput, real-time detection of Naegleria lovaniensis in natural river water using LED-illuminated Fountain FlowTMCytometry

AIMS

To test Fountain Flow Cytometry (FFC) for the rapid and sensitive detection of Naegleria lovaniensis amoebae (an analogue for Naegleria fowleri) in natural river waters.

METHODS AND RESULTS

Samples were incubated with one of two fluorescent labels to facilitate detection: ChemChrome V6, a viability indicator, and an R-phycoerytherin (RPE) immunolabel to detect N. lovaniensis specifically. The resulting aqueous sample was passed as a stream in front of a light-emitting diode, which excited the fluorescent labels. The fluorescence was detected with a digital camera as the sample flowed toward the imager. Detections of N. lovaniensis were made in inoculated samples of natural water from eight rivers in France and the United States. FFC enumeration yielded results that are consistent with other counting methods: solid-phase cytometry, flow cytometry, and hemocytometry, down to concentrations of 0.06 amoebae ml(-1), using a flow rate of 15 ml min(-1).

CONCLUSIONS

This study supports the efficacy of using FFC for the detection of viable protozoa in natural waters and indicates that use of RPE illuminated at 530 nm and detected at 585 nm provides a satisfactory means of attenuating background.

SIGNIFICANCE AND IMPACT OF THE STUDY

Because of the severe global public health issues with drinking water and sanitation, there is an urgent need to develop a technique for the real-time detection of viable pathogens in environmental samples at low concentrations. FFC addresses this need.

Quantitative Detection and Differentiation of Free-Living Amoeba Species Using SYBR Green–Based Real-Time PCR Melting Curve Analysis

Real-time polymerase chain reaction melting curve analysis (MCA) allows differentiation of several free-living amoebae species. Distinctive characteristics were found for Naegleria fowleri, N. lovaniensis, N. australiensis, N. gruberi, Hartmanella vermiformis, and Willaertia magna. Species specificity of the amplicons was confirmed using agarose gel electrophoresis and sequence-based approaches. Amplification efficiency ranged from 91% to 98%, indicating the quantitative potential of the assay. This MCA approach can be used for quantitative detection of free-living amoebae after cultivation but also as a culture-independent detection method.

Rapid, sensitive, and discriminating identification of Naegleria spp. by real-time PCR and melting-curve analysis

The free-living amoeboflagellate genus Naegleria includes one pathogenic and two potentially pathogenic species (Naegleria fowleri, Naegleria italica, and Naegleria australiensis) plus numerous benign organisms. Monitoring of bathing water, water supplies, and cooling systems for these pathogens requires a timely and reliable method for identification, but current DNA sequence-based methods identify only N. fowleri or require full sequencing to identify other species in the genus. A novel closed-tube method for distinguishing thermophilic Naegleria species is presented, using a single primer set and the DNA intercalating dye SYTO9 for real-time PCR and melting-curve analysis of the 5.8S ribosomal DNA gene and flanking noncoding spacers (ITS1, ITS2). Collection of DNA melting data at close temperature intervals produces highly informative melting curves with one or more recognizable melting peaks, readily distinguished for seven Naegleria species and the related Willaertia magna. Advantages over other methods used to identify these organisms include its comprehensiveness (encompassing all species tested to date), simplicity (no electrophoresis required to verify the product), and sensitivity (unambiguous identification from DNA equivalent to one cell). This approach should be applicable to a wide range of microorganisms of medical importance.

Isolation and molecular identification of free-living amoebae of the genus Naegleria from Arctic and sub-Antarctic regions

Twenty-three freshwater samples with sediment taken from two regions in the Arctic, Spitzbergen and Greenland, and one region in sub-Antarctica, Ile de la Possession, were cultured for amoebae at 37 degrees C and room temperature (RT). Only two samples yielded amoebae at 37 degrees C and the two isolates were identified from their morphological features to belong to the genus Acanthamoeba. Vahlkampfiid amoebae were isolated from 11 samples at RT. Morphological analysis of the cysts identified all 11 isolates as belonging to the genus Naegleria, although only about half of them (45%) transformed into flagellates. Ribosomal DNA sequence analysis demonstrated that these isolates represent novel species and that N. antarctica, N. dobsoni and N. chilensis are their closest relatives. Not surprisingly, these three species also grow at lower temperatures (<37 degrees C) than the majority of described Naegleria spp. Two of the eight new species were found in both Arctic and sub-Antarctic regions, and other new species from the Arctic are closely related to new species from the sub-Antarctic. Therefore, it seems the Naegleria gene pool present in the polar regions is different from that found in temperate and tropical regions.

Morphologic and Molecular Identification ofNaegleria dunnebackein. sp. Isolated from a Water Sample

Naegleria dunnebackei n. sp., a new species of the free-living amoeboflagellate Naegleria, is described in this report. The organism was isolated from a water sample taken from drinking troughs associated with cases of primary amoebic meningoencephalitis in cattle at a ranch in southern California. The isolate grew at, but not above 37 degrees C, and did not kill young mice upon intranasal inoculation suggesting that it was not pathogenic. The new species combines morphological features of non-pathogenic Naegleria gruberi and pathogenic Naegleria fowleri. The trophic amoeba resembled other members of the genus, with a prominent vesicular nucleus and mitochondria with discoidal cristae; a Golgi apparatus was not observed by electron microscopy. The cyst stage had pores in the wall typical of those seen in pathogenic N. fowleri. Upon suspension in distilled water, amoebae transformed into temporary, non-feeding flagellates, mostly with two anterior flagella but occasionally with four. The rationale for its description as a new species was based upon sequencing of the 5.8S rDNA and internal transcribed spacers of the amoeba, which is similar to but not identical to that of Naegleria gallica, differing from that organism's DNA by six base pairs. Virus-like elements were found in the cytoplasm of trophic amoebae, often in association with crystalloids, and may be the cause of lysis of amoebae in culture.

The isolation of Naegleria italica from Peru indicates that this potentially pathogenic species occurs worldwide

The amoeboflagellate genus Naegleria includes a few species that are virulent in experimental animals. One of these species, Naegleria italica, has been isolated from the environment only in Italy and Australia. I report here the isolation of a strain of N. italica from a water sample collected in Peru. This broadens the occurrence of this species to encompass three different continents. This new N. italica isolate from Peru has the same ITS1, 5.8S rDNA and ITS2 sequence as that of the type strain from Italy and the isolate from Australia. From the same water body in Peru a Naegleria strain was isolated that differs from N. italica by only one additional base pair in the ITS2 sequence. The maximum growth temperature tolerated by this particular isolate is 40 degrees C, which is different from that of N. italica, which is 42 degrees C.

An exotic sinusitis

We report a case of sinusitis caused by mixed free-living amoebae, Acanthamoeba and Naegleria, in an immunocompetent host; this has not been documented before. Free-living amoebae should be considered in the differential diagnosis of pathogens that cause sinusitis with or without central nervous system involvement, especially when bacteria or fungi are not found by smear, biopsy or culture.

Early detection and identification of amphizoic amoebae from nasal exudates of a symptomatic case

A man visited the Out Patient Department of the hospital for Tropical Diseases in February 2004 with low grade fever and severe headache for a week. He had the history of diving in a natural pond 2-3 days before the onset of the disease. A thick bloody mucous was observed from the nasal discharge. Fresh microscopic observation of the exudates in 0.85% sodium chloride revealed numerous active amoeba trophozoites. Two groups of the trophozoites were observed The first group was 10 micro sized amoeba with active directional movement by lobopodia and the second group was 15-30 micro sized amoeba with active multiprogressive movement by filopodia. Few flagellate forms were observed after exflagellation in distilled water and some polygonal cysts were also found. Giemsa' stain was used to differentiate the amoeba trophozoites from the leukocytes. It was concluded that this patient was infected by both Naegleria spp. and Acanthamoeba spp. This is the first report of double infection of free-living amoeba in a symptomatic and non-fatal patient.

Free-living ameba contamination in natural hot springs in Thailand

Thermo tolerant free-living ameba, Naegleria spp and Acanthamoeba spp contamination in natural hot springs in Thailand were carried out from 13 provinces. The temperature of hot springs water varied from 28 degrees-65 degrees C and pH from 6-8. We found that 38.2 % (26/68) of water samples were positive, Acanthamoeba was 13.2% (9/68) whilst Naegleria was 35.3% (24/68). Contamination by free-living ameba in natural hot springs may pose a significant health risk to people who use such water for recreation activities.

Spa, springs and safety

Natural mineral water has long been used worldwide for bathing and health purposes. At present, Thailand is famous for health spas and natural hot springs among local people and tourists. Due to possible risks of exposure to harmful agents, we studied hazardous pollutants at 57 natural hot springs from 11 provinces in northern, central, eastern and southern Thailand. Pathogenic, free-living amebae of the genera Naegleria and Acanthamoeba, which can cause central nervous system infection, were found in 26.3% (15/57) and 15.8% (9/ 57), respectively. Dissolved radon, a soil gas with carcinogenic properties, was present in nearly all hot springs sites, with concentration ranging from 0.87-76,527 Becquerels/m3. There were 5 water samples in which radon concentration exceeded the safety limit for drinking. Legionella pneumoniphila (serogroups 1, 3, 5, 6, 7 10 and 13) were found in samples from 71.9% (41/57) of studied sites. Because spas and natural springs are popular tourist attractions, health authorities should be aware of possible hazards and provide tactful measures and guidelines to ensure safety without causing undue alarm to foreign and Thai tourists.

Detection of Naegleria sp. in a thermal, acidic stream in Yellowstone National Park

An initial survey of sequences of PCR-amplified portions of the 18S rRNA genes from a community DNA clone library, prepared from an algal mat in a thermal, acidic stream in Yellowstone National Park, WY, USA, revealed among other sequences, several that matched Vahlkampfia. This finding prompted further investigation using primers specific for Naegleria. Sequences from a subsequent DNA clone library, prepared from the 5.8S rRNA gene and the adjacent internal transcribed spacer (ITS) regions of the rRNA, closely matched Naegleria and formed an independent lineage within a clade containing Naegleria sturti and Naegleria niuginiensis. The sequences may represent a new Naegleria species.

Genetic variations in the internal transcribed spacer and mitochondrial small subunit rRNA gene of Naegleria spp

Naegleria spp. are widely distributed free-living amebas, but one species in the genus, N. fowleri, causes acute fulminant primary amebic meningoencephalitis in humans and other animals. Thus, it is important to differentiate N. fowleri from the rest in the genus of Naegleria, and to develop tools for the detection of intra-specific genetic variations. In this study, one isolate each of N. australiensis, N. gruberi, N. jadini, and N. lovaniensis and 22 isolates of N. fowleri were characterized at the internal transcribed spacers (ITS) and mitochondrial small subunit rRNA (mtSSU rRNA) gene. The mtSSU rRNA primers designed amplified DNA of all isolates, with distinct sequences obtained from all species examined. In contrast, the ITS primers only amplified DNA from N. lovaniensis and N. fowleri, with minor sequence differences between the two. Three genotypes of N. fowleri were found among the isolates analyzed in both the mtSSU rRNA gene and ITS. The extent of sequence variation was greater in the mtSSU rRNA gene, but the ITS had the advantage of length polymorphism. These data should be useful in the development of molecular tools for rapid species differentiation and genotyping of Naegleria spp.

Detection and significance of the potentially pathogenic amoeboflagellate Naegleria italica in Australia

Thermophilic amoeboflagellates in the genus Naegleria include both virulent and benign species. One of the less studied species, N. italica, has not been detected in the environment since the first reports from Italy in the 1980s; its virulence is known only from infection of laboratory mice. Two recent strains from recreational water in Western Australia (AWQC NG960, NG961) were tentatively identified as N. italica from the characteristic mobilities of seven isozymes. Sequences of the 5.8S rRNA gene and its flanking ITS aligned with a 380+bp length of the published sequence for N. italica with 98% identity. Differences from the type strain were confined to ITS2. Shorter alignments (<320 bp) were observed with other Naegleria species, corresponding to conserved regions of the 5.8S gene and ITS. Unlike the European type strain of N. italica, the Australian isolates failed to infect laboratory mice intranasally, confirming that infectivity of this species is variable and often lower than in N. fowleri.

Molecular Definition and the Ubiquity of Species in the Genus

To investigate the variability within species of the genus Naegleria, the ITS1,5.8S and ITS2 rDNA were sequenced of several strains of N. lovaniensis and its Western Australian variants, N. australiensis, N. fowleri, N. andersoni, N. jamiesoni, N. tihangensis, N. pringsheimi, N. pagei, N. gruberi sensu lato and a Naegleria lineage that lost a group I intron from the SSUrDNA twintron. As a result, it is possible to define a molecular species within the Naegleria genus. In addition, one strain of each different allozyme cluster was sequenced to investigate whether they belong to described species or should be treated as distinct new species. This leads to the proposal of eleven new species. The sequencing results from those Naegleria spp. of which several strains are available indicate that these species are ubiquitous. The only exception might be the species represented by the WA variants. However, there are still many Naegleria spp. for which only one strain has been isolated, hence, it is important that the search for more isolates should be continued worldwide.

PCR detection and analysis of the free-living amoeba Naegleria in hot springs in Yellowstone and Grand Teton National Parks

Free-living thermotolerant amoebae pose a significant health risk to people who soak and swim in habitats suitable for their growth, such as hot springs. In this survey of 23 different hot springs in Yellowstone and Grand Teton National Parks, we used PCR with primer sets specific for Naegleria to detect three sequence types that represent species not previously described, as well as a fourth sequence type identified as the pathogen Naegleria fowleri.

Effect of antifungal drugs on pathogenic Naegleria spp isolated from natural water sources

Five of 16 strains of pathogenic Naegleria spp isolated from 350 natural water sources in Taling Chan District, Bangkok had similar molecular weights and zymogram patterns to those of Naegleria fowleri CDCVO 3081 and Thai strain. The in vitro effects of antifungal drugs (amphotericin B, ketoconazole, fluconazole and itraconazole) were tested at the following concentrations: amphotericin B 0.01-0.55 microg/ml, ketoconazole 0.01-0.3 microg/ml, fluconazole 0.75-3.5 mg/ml and itraconazole 4-12 mg/ml respectively. Aliquots (15,000 cells/ml) of the amoebae were placed in the cells of the microtiter plate and incubated at 37 degrees C. Amoebae from each treatment sample were exposed to one of the four antifungal drugs. Statistical analysis was done by dependent t-test. The sensitivity of the antifungal drugs (MIC50) was as follows: amphotericin B 0.03-0.035 microg/ml ketoconazole 0.05-0.15 microg/ml fluconazole 1.75 mg/ml and itraconazole 8-9 mg/ml respectively (p < 0.005).

CONCLUSION

Amphotericin B and ketoconazole are more active against Naegleria fowleri in vitro. The results of the present study should be used as an in vitro screening test for drugs that have potential amebicidal activity.

[Isolation of potencially pathogenic free-living amoebas in hospital dust]

OBJECTIVE

To evaluate the occurrence of free-living amoebas of the genera Acanthamoeba and Naegleria is dust samples colleted in two hospitals.

METHODS

One-hundred and thirty-two dust samples were collected in two hospitals in Brazil. Hospital collection sites were the following: intensive care unit, operation rooms, nursery, kitchen, emergency and infectious diseases isolation room. The isolation of the amoebas was performed in three culture media: non-nutrient agar inoculated with Escherichia coli, soy agar, and microculture in Giazzi-modified Pavlova's medium. The amoebas were identified according to morphological criteria.

RESULTS

Amoebas of the genera Acanthamoeba and Naegleria were found in 45.5% of the samples, of which 41.6% were collected in the university hospital and 50% in the state hospital. Of all, 45.5% were positive for the genera Acanthamoeba and 3.8% for genera Naegleria.

CONCLUSIONS

Potentially pathogenic free-living amoebas were seen in all sites of the two hospitals and Acanthamoeba was the most frequently isolated genera.

December 2002: 19-year old male with febrile illness after jet ski accident

The December 2002 COM. A 19-year-old healthy male fell into stagnant water of the intercostal waterway (salt water of South Florida), following a jet ski accident. He sustained minor superficial injuries but engulfed significant quantities of water and sediment. A few days later he developed bifrontal headaches, vomiting, a stiff neck and a temperature of 102 degrees F. A CT scan on admission without contrast was negative. The CSF had markedly elevated white count but bacterial and fungal cultures were negative. He became progressively lethargic. On the fifth day he developed seizure activity. He expired the next day despite antibiotics. Gross examination of the brain at autopsy revealed edema, cerebellar tonsillar herniation and purulent meningitis. Microscopic examination revealed a massive leptomeningeal inflammatory infiltrate composed of neutrophils, lymphocytes, and numerous histiocyte-like cells. The inflammatory infiltrate extended into the cerebral parenchyma in numerous areas also involving the cerebellum, brainstem and ventricular system. Given the exposure to stagnant water (later confirmed to be a man-made fresh water lake), and the numerous histiocytic-like cells, suspicion for an amebic etiology of the disease process was raised and the CDC identified the ameba as Naegleria Fowleri. Infection by Naegleria Fowleri, a free-living ameba, occurs after exposure to polluted water in man-made fresh water lakes, ponds, swimming pools, particularly during the warm weather months when the thermophilic ameba grows well. The pathologic substrate of the infection is an acute hemorrhagic, necrotizing meningo-encephalitis mainly at the base of the brain, brainstem and cerebellum occurring in young, healthy individuals.

A brief survey of free-living amebae in Thailand and Hamamatsu District, Japan

The aim of this study was to determine the presence of free-living amebae in aquatic habitats of human environments in Thailand and Hamamatsu district, Japan. Genus identification was based on the morphology of cyst and trophozoite forms and a flagellation test for genus Naegleria. The pathogenic potential was tested in mice by nasal instillation for genus Naegleria and Acanthameba. In 14 provinces of Thailand, amebae were isolated in 43 from 95 water samples and 67 from 120 soil swabs. Amebae of 49 isolates from waters were identified as Acanthameba (36.7%), Naegleria (28.6%), Hartmannella (20.4%), Vahlkampfia (12.2%) and Vannella (2%). Soil samples have significantly higher levels of Acanthameba and Hartmannella (p<0.05) but lower for Naegleria (p<0.05) and 7 unidentified amebae were found. In Hamamatsu district, Japan, 62 amebae of the same genera were isolated from 47 of 95 water samples. There were significantly higher levels of Acanthameba (22.6%) (p<0.05) but lower for Naegleria (4.8%) (p<0.05) than those of Thailand which each of them caused death in mice. Three unidentified amebae were isolated. This finding serves as additional evidence for the presence of free-living amebae under natural and the difference in distribution between tropic and subtropic areas.

Elimination of free-living amoebae in fresh water with pulsed electric fields

This study investigates the effects of pulsed electric fields on the inactivation of trophozoite form of Naegleria lovaniensis Ar9M-1 in batch and flow processes, systematically examining the lethal effect of field strength, pulse duration, number of pulses, and pulse frequency. Our results show that amoebae eradication is modulated by pulse parameters, composition of the pulsing medium, and physiological state of the cells. Cell survival is not related to the energy delivered to the cell suspension during the electrical treatment. For a given energy a strong field applied for a short cumulative pulse duration affects viability more than a weak field with a long cumulative pulsation. We also determine the optimal electrical conditions to obtain an inactivation rate higher than 95% while using the least energy. Flow processes allow to treat large-scale volumes. Our results show that the most efficient flow process for amoeba eradication requires a field parallel to the flow. Pulsed electric fields are a new and attractive method for inactivating amoebae in large volumes of fresh water.

Use of multiplex PCR and PCR restriction enzyme analysis for detection and exploration of the variability in the free-living amoeba Naegleria in the environment

A multiplex PCR was developed to simultaneously detect Naegleria fowleri and other Naegleria species in the environment. Multiplex PCR was also capable of identifying N. fowleri isolates with internal transcribed spacers of different sizes. In addition, restriction fragment length polymorphism analysis of the PCR product distinguished the main thermophilic Naegleria species from the sampling sites.

Development of 18S rRNA-targeted oligonucleotide probes for specific detection of Hartmannella and Naegleria in Legionella-positive environmental samples

Aquatic protozoa are natural hosts of the human pathogen Legionella pneumophila. The fluorescence labeled 16S rRNA-targeted oligonucleotide probe LEGPNE1 has recently been shown to specifically detect extracellular legionellae as well as intracellular legionellae parasitizing protozoa. In this study we designed oligonucleotide probes which are complementary to distinct regions of the 18S rRNA of the Legionella host organisms of the genera Hartmannella and Naegleria. The specificity of the probes, HART498 and NAEG1088, was tested by in situ hybridization of various laboratory reference strains. In order to evaluate the fluorescent probes for environmental studies three selected Legionella-positive cold water habitats were examined for the presence of these protozoa. Traditional culture methods followed by morphological identification revealed an almost consistent presence of Naegleria spp. in cold water habitats. Other protozoa species including Acanthamoeba spp., Echinamoeba spp., Hartmannella spp., Platyamoeba placida, Saccamoeba spp., Thecamoeba quadrilineata, and Vexillifera spp. were found sporadically. Concomitant analysis of the pH, conductivity and temperature of the water samples revealed no preference of Legionella or the respective protozoa for certain environmental conditions. The specificity of the newly designed 18S rRNA probes demonstrates that they are valuable and rapid tools for the identification of culturable environmental protozoa.

Isolation and identification by partial sequencing of the 18S ribosomal gene of free-living amoebae from necrotic tissue of Basilliscus plumifrons (Sauria: Iguanidae)

A 3-year-old Basiliscus plumifrons developed a necrotic lesion on the tail resulting from nodules of unknown etiology. Investigation of necrotic tissue revealed several gram-negative bacteria as well as three different species of free-living amoebae. The amoebae were identified by morphological characters as belonging to the genera Acanthamoeba, Echinamoeba, and Naegleria, respectively. Partial sequencing of the 18S ribosomal gene was performed for reliable systematic determination. Two of the isolates showed thermotolerance. No isolate was growable in conventional liquid media, but the Acanthamoeba strain readily grew on a human cell line (HEp2). It remains unclear whether the amoebae fed on the coexisting bacteria or on host tissue.

Non-Acanthamoeba amebic keratitis

PURPOSE

To describe the clinical presentation and outcome of two cases with presumed non-Acanthamoeba amebic keratitis.

METHODS

Case reports.

RESULTS

Both patients presented with typical symptoms and signs of Acanthamoeba keratitis. The patients' soft contact lenses, lens cases, open solutions, and conjunctival samples were cultured. Diagnosis of non-Acanthamoeba amebic keratitis was based on the presence of keratitis and amebic growth from patients' contact lenses of the affected eyes. Amebic culture from the contralateral contact lens was negative. Vahlkampfia cysts were identified in case 1, and Naegleria cysts in case 2. Topical treatment with polyhexamethylene biguanide and propamidine resolved the keratitis in case 1. Case 2 was lost to follow-up.

CONCLUSION

Non-Acanthamoeba amebic keratitis was diagnosed in two patients based on the clinical presentation (resembling Acanthamoeba keratitis), culture of the contact lens, and response to antiamebic treatment (in one case). Keratitis associated with Naegleria contamination of contact lenses has not been previously reported.

Comparison of free-living amoebae in hot water systems of hospitals with isolates from moist sanitary areas by identifying genera and determining temperature tolerance

Legionella-contaminated hot water systems and moist sanitary areas in six hospitals were sampled for amoebae by following a standardized collection protocol. Genus identifications and temperature tolerance determinations were made. Amoebae identified as Hartmannella vermiformis (65%), Echinamoebae spp. (15%), Saccamoebae spp. (12%), and Vahlkampfia spp. (9%) were detected in 29 of 56 (52%) hot water samples. Twenty-three of 49 (47%) swabs obtained from moist areas were amoeba positive. The following genera were identified: Acanthamoeba (22%), Naegleria (22%), Vahlkampfia (20%), Hartmannella (15%), and Vanella (7%). The temperature tolerance of amoebae from hot water systems was strikingly different from that of amoebae from moist areas. At 44 degrees C on agar, 59% of amoebic isolates sampled from hot water systems showed growth. The corresponding value for isolates from moist areas was only 17%. Six Acanthamoeba isolates from the moist areas were considered potential pathogens. Four Hartmannella and two Saccamoeba isolates from hot water could be cultured at 53 degrees C.

Isolation, identification and increasing importance of 'free-living' amoebae causing human disease

Amphizoic small amoebic protozoa are capable of existing both in 'free-living' and in 'parasitic' form depending on the actual conditions. Two genera (Naegleria and Acanthamoeba) have become recognised as opportunist human parasites. Since the first description in 1965 of a lethal case of primary amoebic meningoencephalitis (PAM) caused by Naegleria, many more (mostly lethal) cases have been reported, while granulomatous amoebic encephalitis (GAE), as well as eye (keratinitis, conjunctivitis, etc.), ear, nose, skin and internal organ infections caused by Acanthamoeba have also occurred in rapidly increasing numbers. Both pathogenic and non-pathogenic species of Naegleria and Acanthamoeba are found worldwide in water, soil and dust, where they provide a potential source of infection. Successful differential diagnosis and appropriate (specific) therapy depends on precise laboratory identification of the 'free-living' amoebae. In most cases, isolation from the environment can be achieved, but identification and differentiation of the pathogenic and non-pathogenic strains is not easy. The methods presently available do not fulfil completely the requirements for specificity, sensitivity and reliability. Morphological criteria are inadequate, while thermophilic character, pH dependency and even virulence in infected mice, are not unambiguous features of pathogenicity of the different strains. More promising are molecular methods, such as restriction endonuclease digestion of whole-cell DNA or mitochondrial DNA, as well as iso-enzyme profile analysis after iso-electric focusing and staining for acid phosphatase and propionyl esterase activity. Use of appropriate monoclonal antibodies has also yielded promising results in the differentiation of human pathogenic and non-pathogenic strains. However, quicker, simpler, more specific and reliable methods are still highly desirable. The significance of endosymbiosis (especially with Legionella strains) is not well understood. The results of a systematic survey in Hungary for the isolation and identification of 'free-living' amoebae, including an investigation of the Hungarian amoebic fauna, the isolation of possibly pathogenic Naegleria strains and of some Acanthamoeba strains from eye diseases, as well as the finding of a case of endosymbiosis, are also reported here.

Techniques for isolating thermotolerant and pathogenic freeliving amebae

Several conditions of isolation were evaluated to determine which yielded the greatest number of thermotolerant and pathogenic freeliving amebae. Swab samples, easier to obtain and process, produced more pathogenic amebae than water samples. If water samples are required, 50-ml volumes gave the greatest percentage of pathogenic isolates. An incubating temperature of 42 degrees C yielded the most thermotolerant amebae. A total of 11 pathogenic isolates were obtained from 762 environmental samples and were Acanthamoeba (55%), Naegleria fowleri Carter, 1970 (27%), and N. australiensis De Jonckheere, 1981 (18%).

[Acanthamoeba, naturally intracellularly infected with Pseudomonas aeruginosa, after their isolation from a microbiologically contaminated drinking water system in a hospital]

The drinking water system of a new hospital building that was highly contaminated with bacteria before opening was investigated too for the prevalence of small free living amoebae. Germ counts resulted in > 100 CFU/ml in 100% of the cold water samples, that showed also growth of P. aeruginosa, whereas E. coli and coliforme bacteria could not be identified. The investigation of 37 water samples for protozoa revealed growth of small freeliving amoebae in 20 samples (54%) belonging to 10 species of the genus Acanthamoeba, Naegleria, Hartmannella, Echinamoeba among others. In addition 2 Ciliate- and 2 Microflagellate-species could be observed. While all Naegleria strains isolated belonged to the N. gruberi-complex two of 16 Acanthamoeba-isolates proved to be pathogenic for laboratory mice. From 7 watersamples positive with P. aeruginosa 5 Acanthamoeba- and 2 Echinamoeba strains could be isolated which revealed intracellular multiplication of P. aeruginosa. Because of their well known resistances against chlorine, the amoebae and their cysts are considered to be vectors for these intracellular bacteria. A complete sanitation of the incriminated drinking water system was accomplished by combined chemical and thermic disinfection measures.

Isolation and identification of free-living amoebae from some water sources in Alexandria

Samples from different water sources of Alexandria, and from nasal passages of 500 healthy children inhabiting areas nearby these sources were examined for the presence of free-living amoebae. These samples were cultured on 1.5% non nutrient agar streaked with bacteria. Amoebae were isolated and identified by means of their morphological characters and ability to produce flagellated forms. Characteristics of the cystic stages and pattern of excystation also aided in the identification of the various species. Nine species, Naegleria gruberi, N. fowleri, Acanthamoeba rhysodes, A. glebae, A. culbertsoni, A. astronyxis, A. palestinensis, V. avara and V. inornata were isolated from the water of canals and drains. N. gruberi and A. rhysodes were found in the nasal passages of six healthy children living near the contaminated canals. No amoebae were encountered in the drinking water, swimming pools, sea and lake water included in this study.

Successful treatment of primary amebic meningoencephalitis

The fourth documented survivor of primary amebic meningoencephalitis, a young man with a history of waterskiing in a stagnant freshwater lake in northeastern Pennsylvania, is presented. Early consideration of this unusual diagnosis, based on historical factors (recent contact with warm fresh water), coupled with prompt aggressive therapy with high-dose amphotericin B is emphasized in achieving a successful outcome.

Amplification of repetitive DNA for the specific detection of Naegleria fowleri

By using hybridization at low C0t values, a genomic library on Naegleria fowleri was screened for clones containing repetitive DNA. Partial sequence information from a repetitive clone, Nf9, showed sequence homologies with the mitochondrial ATPase 6 subunit from yeasts and other organisms. Synthetic DNA primers were selected and tested in amplification reactions. Nonstringent hybridization conditions were defined which allowed amplification of N. fowleri DNA and reduced amplification of DNA from nonpathogenic Naegleria species. Stringent conditions were selected which allowed detection only of N. fowleri. Identity of the amplified DNA was confirmed by using internal restriction sites and an internal primer. In a blind study, tissue from mice experimentally infected with N. fowleri was specifically detected by using stringent hybridization conditions.

Differentiation of Naegleria fowleri from Acanthamoeba species by using monoclonal antibodies and flow cytometry

Monoclonal antibodies to Naegleria fowleri and Acanthamoeba polyphaga were analyzed by enzyme-linked immunosorbent assay, indirect immunofluorescence microscopy, and fluorescence flow cytometry to assess specificity and cross-reactivity with axenically cultured N. fowleri and Acanthamoeba spp. Four monoclonal antibodies to N. fowleri were specific for N. fowleri and had no reactivity to A. polyphaga. Similarly, four monoclonal antibodies to A. polyphaga did not react with N. fowleri. Two of the four monoclonal antibodies to A. polyphaga did not react with other Acanthamoeba spp. tested, while two of the antibodies demonstrated a high degree of cross-reactivity with a putative Acanthamoeba castellanii strain by immunofluorescence microscopy; this was confirmed by fluorescence flow cytometry for one of the antibodies. These monoclonal antibodies were used to identify Acanthamoeba trophozoites in infected brain sections of a patient who died of suspected Acanthamoeba-caused granulomatous amoebic encephalitis, demonstrating potential utility in the direct identification of N. fowleri and Acanthamoeba spp. in clinical specimens.

Naegleria lovaniensis tarasca new subspecies, and the purepecha strain, a morphological variant of N. l. lovaniensis, isolated from natural thermal waters in Mexico

Amoebae were isolated from a natural thermal water source in Michoacán, Mexico, in September 1986. Two 500-ml samples were taken from pools with water at 45 degrees C and 46 degrees C and concentrated at 2,000 g for 15 min. The sediment was seeded on nonnutritive agar plates and incubated at 42 degrees C. The isolates were axenized in bactocasitone-serum medium. The identification of the isolates was based on their morphology, total protein and isoenzyme patterns by agarose isoelectric focusing, serology, fine structure, agglutination with Concanavalin A, sensitivity to trimethoprim, capacity to kill mice, and their cytopathic effect in Vero cells. The results showed several morphophysiological, biochemical and serological differences between the isolates and the type strain Aq/9/1/45D of Naegleria lovaniensis. These remarkable differences provide sufficient evidence to consider one of the isolates a new subspecies, and the other one a morphological variant of N. l. lovaniensis, which can be differentiated from other Naegleriae by their morphology, biochemistry, serology and physiology. The authors propose the name tarasca for the subspecies and purepecha for the morphological variant.

[Primary amebic meningoencephalitis caused by Naegleria fowleri in an adolescent from Huetamo, Michoacan, Mexico]

A 13 year old boy died after a three day illness with severe headache, explosive vomiting, fever and progressive loss of consciousness. The autopsy revealed purulent and necrotizing meningoencephalitis mainly involving the basal regions and posterior fossa and on microscopic examination numerous trophozoites of Naegleria were seen in the meninges and necrotic brain tissue. The trophozoites were identified as Naegleria fowleri by immunoperoxidase staining. This case as well as others previously reported in Mexico and the documented presence of Naegleria species from several sources indicate that primary amebic meningoencephalitis should be considered in the differential diagnosis of cases with neurological symptoms of sudden onset.

Nasal carriage of Naegleria fowleri and its environmental occurrence in Borno State, Nigeria

The presence of free living amoebae was investigated in the nasal passages of 50 healthy children and in environmental sources in Maiduguri, Borno State of Nigeria. Three of the children yielded positive cultures of Naegleria fowleri. All the five water samples and two of the nine soil samples examined from different localities were positive for N. fowleri. The isolates proved pathogenic for laboratory mice causing a fatal meningoencephalitis. The epidemiological significance of the findings is discussed.