A survey of pathogenic and free-living amoebae inhabiting swimming pool water in Mexico City

"Nano knife" for efficient piezocatalytic inactivation of amoeba spores and their intracellular bacteria: Synergetic effect between physical damage and chemical oxidation

Microbial interactions between infectious agents severely interfere with the disinfection process, and current disinfection methods are unable to effectively inactivate intracellular pathogens, posing a new threat to drinking water safety. In this study, we first reported the high efficiency of piezocatalysis in inactivating amoebae and their intracellular bacteria. Results showed that the inactivation rates of the MoS2/rGO piezocatalytic system for amoebic spores and their intracellular bacteria were 4.18 and 5.02-log, respectively, within 180 min. Based on scavenger studies and ESR tests, the efficient inactivation of pathogens can be attributed to the generation of reactive oxygen species (ROS), and different pathogens exhibit varying tolerances to distinct ROS. Moreover, TEM analysis revealed that the sharp edge of MoS2/rGO was conducive to the physical cutting of amoeba's cell wall and membrane, promoting the attack of ROS and ensuring a more thorough deactivation. Additionally, the intracellular ROS produced by amoebae is not only conducive to the inactivation of amoebae but also the main reason for the inactivation of bacteria in spores. This study provides a new solution for the inactivation of amoeba spores and their intracellular bacteria and emphasizes the high efficiency of the synergistic effect of physical damage and chemical oxidation.

Prevalence of free-living amoebae in swimming pools and recreational waters, a systematic review and meta-analysis

Free-living amoebae (FLA) are cosmopolitan microorganisms known to be pathogenic to humans who often have a history of contact with contaminated water. Swimming pools and recreational waters are among the environments where the greatest human exposure to FLA occurs. This study aimed to determine the prevalence of FLA in swimming pools and recreational waters, through a systematic review and meta-analysis that included studies published between 1977 and 2022. A total of 106 studies were included and an overall prevalence of FLA in swimming pools and recreational waters of 44.34% (95% CI = 38.57–50.18) was found. Considering the studies published up to 2010 (1977–2010), between 2010 and 2015, and those published after 2010 (> 2010–2022), the prevalence was 53.09% (95% CI = 43.33–62.73) and 37.07% (95% CI = 28.87–45.66) and 45.40% (95% CI = 35.48–55.51), respectively. The highest prevalence was found in the American continent (63.99%), in Mexico (98.35%), and in indoor hot swimming pools (52.27%). The prevalence varied with the variation of FLA detection methods, morphology (57.21%), PCR (25.78%), and simultaneously morphology and PCR (43.16%). The global prevalence by genera was Vahlkampfia spp. (54.20%), Acanthamoeba spp. (33.47%), Naegleria spp. (30.95%), Hartmannella spp./Vermamoeba spp. (20.73%), Stenamoeba spp. (12.05%), and Vannella spp. (10.75%). There is considerable risk of FLA infection in swimming pools and recreational waters. Recreational water safety needs to be routinely monitored and, in case of risk, locations need to be identified with warning signs and users need to be educated. Swimming pools and artificial recreational water should be properly disinfected. Photolysis of NaOCl or NaCl in water by UV-C radiation is a promising alternative to disinfect swimming pools and artificial recreational waters.

Evaluation of the occurrence of pathogenic free-living amoeba and bacteria in 20 public indoor swimming pool facilities

Recently, indoor swimming pool activities have increased to promote health-enhancing physical activities, which require establishing suitable protocols for disinfection and water quality control. Normally, the assessment of the microbial quality of the water in the pools only considers the presence of different bacteria. However, other less frequent but more resistant pathogens, such as free-living amoebas (FLA), are not contemplated in both existing recommendation and research activities. FLA represent a relevant human health risk, not only due to their pathogenicity but also due to the ability to act as vehicles of other pathogens, such as bacteria. Therefore, this work aimed to study the physicochemical characteristics and the occurrence of potentially pathogenic FLA and bacteria in water samples from 20 public indoor swimming facilities in Northern Portugal. Our results showed that some swimming pools presented levels of pH, free chlorine, and conductivity out of the recommended limits. Pathogenic FLA species were detected in two of the facilities under study, where we also report the presence of both, FLA and pathogenic bacteria. Our findings evidence the need to assess the occurrence of FLA and their existence in the same environmental niche as pathogenic bacteria in swimming pool facilities worldwide and to establish recommendations to safeguard the health of the users.

Development of a new TaqMan PCR assay for the detection of both Entamoeba gingivalis genotypes

Entamoeba gingivalis is a parasitic protozoan found in the mouth of patients suffering from periodontitis, a widespread oral disease with an underestimated prevalence and major consequences on health. We present the development of the first TaqMan PCR assay targeting both E. gingivalis subtypes. This method has been evaluated on 50 samples from patients diagnosed with periodontitis in comparison with 2 different conventional PCRs, and a real-time SYBR Green PCR. Fifty percent of the samples were found positive for the E. gingivalis ST1 subtype with this new PCR, the SYBR Green PCR and one of the conventional PCRs. Among the 25 remaining samples, 12 (24%) were found positive for the E. gingivalis ST2 kamaktlii variant. This new TaqMan PCR could be used before and after periodontitis treatment to follow its efficacy and measure the parasite load in order to better understand the role of these parasites in oral diseases.

Exotic Tourist Destinations and Transmission of Infections by Swimming Pools and Hot Springs-A Literature Review

A growing number of people undertake international travel, and yet faster growth of such travel is expected in the tropics. Information on the hazards presented by pool and hot spring waters in tropical countries is very limited. This review aims to collate available information on pool water quality, alongside data on cases and outbreaks associated with swimming in pools in tropical regions affecting both local populations and travellers. Bacteria species commonly causing cases and outbreaks in the tropics as well as elsewhere in the world were excluded, and the review focuses on studies related to pathogens that, with the exception of Cryptosporidium, are unusual in more temperate climates. Studies concerning subtropical countries were included in the light of climate change. Diseases transmitted by vectors breeding in poorly maintained, neglected or abandoned pools were also included. 83 studies dealing with Microsporidia, Leptospira spp., Schistosomas spp., Cryptosporidium spp., Acanthamoeba spp., Naegleria spp., Clostridium trachomatis, viruses, and vectors breeding in swimming pool and hot tub waters, and fulfilling predefined criteria, have been included in our survey of the literature. In conclusion, prevention strategies for pool safety in the tropics are imperative. Public health authorities need to provide guidance to westerners travelling to exotic destinations on how to protect their health in swimming pools.

Presence of trichomonads in subgingival biofilm of patients with periodontitis: preliminary results

This study aims to evaluate the prevalence of trichomonads in the subgingival biofilm of patients with periodontitis. Secondarily, the trichomonad presence was related to patient characteristics and periodontal clinical parameters, in order to highlight the factor favoring the development of these protozoans. Subgingival biofilm samples were collected from at least two diseased and one healthy site in 50 patients suffering from periodontitis. Trichomonads were identified using phase contrast microscopy. All patient characteristics and periodontal clinical parameter data were then statistically analyzed. From the 50 patients examined, 195 sites were sampled, including 145 diseased ones. Trichomonads were only observed on 16 of the 145 diseased sites (11%) and none in the other 50 healthy sites. Based on these results, 20% (n = 10) of patients were positive for the presence of trichomonads from at least one of the diseased sites collected. Tooth mobility, substantial supra-gingival dental deposits, and severe clinical attachment loss were statistically associated with trichomonad presence. If the subgingival biofilm of male patients over the age of 50 seemed to be more frequently contaminated with trichomonads, this data was not statistically supported. This preliminary study indicates for the first time that in periodontitis-involved patients, trichomonads are observed in the subgingival biofilm collected from diseased sites with severe bone loss, but not from healthy teeth. Further investigations are needed to fully explore the role of this microorganism in the etiology of periodontal disease.

Water-borne protozoa parasites: The Latin American perspective

Health systems, sanitation and water access have certain limitations in nations of Latin America (LA): typical matters of developing countries. Water is often contaminated and therefore unhealthy for the consumers and users. Information on prevalence and detection of waterborne parasitic protozoa are limited or not available in LA. Only few reports have documented in this field during the last forty years and Brazil leads the list, including countries in South America and Mexico within Central America region and Caribbean islands. From 1979 to 2015, 16 outbreaks of waterborne-protozoa, were reported in Latin American countries. T. gondii and C. cayetanensis were the protozoa, which caused more outbreaks and Giardia spp. and Cryptosporidium spp. were the most frequently found protozoa in water samples. On the other hand, Latin America countries have not got a coherent methodology for detection of protozoa in water samples despite whole LA is highly vulnerable to extreme weather events related to waterborne-infections; although Brazil and Colombia have some implemented laws in their surveillance systems. It would be important to coordinate all surveillance systems in between all countries for early detection and measures against waterborne-protozoan and to establish effective and suitable diagnosis tools according to the country's economic strength and particular needs.

Biology and pathogenesis of Naegleria fowleri

Naegleria fowleri is a protist pathogen that can cause lethal brain infection. Despite decades of research, the mortality rate related with primary amoebic meningoencephalitis owing to N. fowleri remains more than 90%. The amoebae pass through the nose to enter the central nervous system killing the host within days, making it one of the deadliest opportunistic parasites. Accordingly, we present an up to date review of the biology and pathogenesis of N. fowleri and discuss needs for future research against this fatal infection.

Neglected waterborne parasitic protozoa and their detection in water

Outbreak incidents raise the question of whether the less frequent aetiological agents of outbreaks are really less frequent in water. Alternatively, waterborne transmission could be relevant, but the lack of attention and rapid, sensitive methods to recover and detect the exogenous stages in water may keep them under-recognized. High quality information on the prevalence and detection of less frequent waterborne protozoa, such as Cyclospora cayetanensis, Toxoplasma gondii, Isospora belli, Balantidium coli, Blastocystis hominis, Entamoeba histolytica and other free-living amoebae (FLA), are not available. This present paper discusses the detection tools applied for the water surveillance of the neglected waterborne protozoa mentioned above and provides future perspectives.

Distribution of Legionella pneumophila bacteria and Naegleria and Hartmannella amoebae in thermal saline baths used in balneotherapy

The present study was aimed at investigating the coexistence and interactions between free living amoebae of Naegleria and Hartmannella genera and pathogenic Legionella pneumophila bacteria in thermal saline baths used in balneotherapy in central Poland. Water samples were collected from November 2010 to May 2011 at intervals longer than 1 month. The microorganisms were detected with the use of a very sensitive fluorescence in situ hybridisation method. In addition, the morphology of the amoebae was studied. Despite relatively high salinity level, ranging from 1.5 to 5.0 %, L. pneumophila were found in all investigated baths, although their number never exceeded 10⁶ cells dm⁻³. Hartmannella were not detected, while Naegleria fowleri were found in one bath. The observation that N. fowleri and L. pneumophila may coexist in thermal saline baths is the first observation emphasising potential threat from these microorganisms in balneotherapy.

Good visual outcome after prompt treatment of acanthamoeba keratitis associated with overnight orthokeratology lens wear

PURPOSE

To describe a patient with a good visual outcome after prompt treatment of Acanthamoeba keratitis as a complication of overnight orthokeratology lens wear.

METHODS

Interventional case report.

RESULTS

A 9-year-old boy experienced pain, photophobia, and redness in his right eye 3 days after visiting a swimming pool. He had been wearing overnight orthokeratology lenses for 5 months for the correction of moderate myopia in both eyes. On examination, best-corrected visual acuity in the right eye was 20/40. A diagnosis of Acanthamoeba keratitis with the presence of the classic feature of perineural infiltrates was made. The patient responded well to treatment with polyhexamethylene biguanide and propamidine isethionate (Brolene). Culture of corneal scrapings and contact lens solution showed heavy growth of Acanthamoeba. Treatment was tapered gradually during the next 4 months, and the final best-corrected visual acuity was 20/25.

CONCLUSIONS

Acanthamoeba keratitis may be a vision-threatening complication associated with overnight orthokeratology lens wear. It is essential for eye care professionals to fully explain and warn parents of the potential downsides that may be associated with orthokeratology. Ophthalmologists should have a high level of suspicion of this complication because prompt diagnosis and treatment can result in good visual outcome.

Induction of morphological and electrophysiological changes in hamster cornea after in vitro interaction with trophozoites of Acanthamoeba spp

Acanthamoeba castellani and Acanthamoeba polyphaga are free-living amebae that cause keratitis and granulomatous encephalitis in humans. We have analyzed the early morphological and electrophysiological changes occurring during the in vitro interaction of cultured amebae with intact or physically damaged corneas obtained from hamsters. Both species of Acanthamoeba produced similar cytopathic changes, as seen by light microscopy and scanning electron microscopy. After adhesion to the epithelial surface, trophozoites formed clumps and migrated toward the cell borders, causing the separation of adjacent cells at 1 h of coculture. At later stages (2 to 4 h), some amebae were found under desquamating epithelial cells whereas others were seen associated with damaged cells or forming amebostome-like structures to ingest detached epithelial cells. Control corneas incubated in culture medium conditioned with amebae showed a cytoplasmic vacuolization and blurring of the epithelial-stromal junction. The early stages of corneal epithelial damage caused by amebae were also analyzed by measuring the transepithelial resistance changes in corneas mounted in Ussing chambers. Both species of Acanthamoeba caused a rapid decrease in electrical resistance. The present observations demonstrate that under in vitro conditions, Acanthamoeba trophozoites rapidly cause significant damage to the corneal epithelium. Furthermore, in our experimental model, previous physical damage to the corneas was not a prerequisite for the development of amebic corneal ulcerations.

Health effects of Acanthamoeba spp. and its potential for waterborne transmission

Risk from Acanthamoeba keratitis is complex, depending upon the virulence of the particular strain, exposure, trauma, or other stress to the eye, and host immune response. Bacterial endosymbionts may also play a factor in the pathogenicity of Acanthamoeba. Which factor(s) may be the most important is not clear. The ability of the host to produce IgA antibodies in tears may be a significant factor. The immune response of the host is a significant risk factor for GAE infection. If so, then a certain subpopulation with an inability to produce IgA in the tears may be at greatest risk. There was no sufficient data on the occurrence or types of Acanthamoeba in tapwater in the U.S. Published work on amoebal presence in tapwater does not provide information on the type of treatment the water received or the level of residual chlorine. Assessment of the pathogenicity by cell culture and molecular methods of Acanthamoeba in tapwater would also be useful in the risk assessment process for drinking water. The possibility that Acanthamoeba spp. might serve as vectors for bacterial infections from water sources also should be explored. The bacterial endosymbionts include an interesting array of pathogens such as Vibrio cholerae and Legionella pneumophila, both of which are well recognized waterborne/water-based pathogens. Work is needed to determine if control of Acanthamoeba spp. is needed to control water-based pathogens in water supplies.

Tear IgA and serum IgG antibodies against Acanthamoeba in patients with Acanthamoeba keratitis

PURPOSE

Exposure to Acanthamoebaspecies appears to be ubiquitous, as 50% to 100% of healthy human subjects display anti-Acanthamoebaantibodies. However, the presence of specific anti-Acanthamoebaantibodies in the serum and tears of patients has not been investigated. The prevalence of serum immunoglobulin G (IgG) and tear IgA against three species of Acanthamoebawas assessed in healthy subjects and patients with Acanthamoebakeratitis.

METHODS

The level of specific serum IgG and tear IgA against A. castellanii, A. astronyxis, and A. culbertsoniin the sera of 23 patients and 25 healthy subjects was tested by enzyme-linked immunosorbent assays. Total serum IgM, IgG, and IgA concentrations were measured by nephelometry. Acanthamoebakeratitis was diagnosed clinically and confirmed by in vivo confocal microscopy. In some patients, corneal biopsies were also performed and trophozoites were cultured on lawns of Escherichia colion non-nutrient agar.

RESULTS

All healthy subjects and patients with Acanthamoebakeratitis had detectable serum IgG antibodies against all Acanthamoebaantigens. However, patients with Acanthamoebakeratitis had significantly higher anti-AcanthamoebaIgG antibody titers than healthy subjects. In contrast, Acanthamoeba-specific tear IgA was significantly lower in patients with Acanthamoebakeratitis in comparison with healthy subjects. Total serum immunoglobulins did not differ significantly between healthy subjects and patients with Acanthamoebakeratitis.

CONCLUSIONS

The results suggest that a low level of anti-AcanthamoebaIgA antibody in the tears appears to be associated with Acanthamoebakeratitis.

Behind the discovery of "Nissenbaum's fixative"

The author describes the serendipitous discovery, conception, development, and history of Nissenbaum's Fixative while an undergraduate biology major in the early 1950s. The subsequent uses, applications, and modifications over the past forty-seven years are also described. Some of the modifications omitted from his short original paper are mentioned. Highlights of his subsequent career in the field of medicine are noted.

Effect of contact lens preservatives on Acanthamoeba

Single preservatives used in contact lens solutions were evaluated for their effectiveness in killing Acanthamoeba castellanii and Acanthamoeba polyphaga trophozoites and cysts. Preservatives were tested against amoebae at intervals varying from 30 minutes to 24 hours. The preservatives were tested with axenically and nonaxenically grown organisms. Chlorhexidine (0.001% and 0.005%), polyaminopropyl biguanide (0.0015%), benzalkonium chloride (0.001% and 0.004%), and hydrogen peroxide (3%) were very effective preservatives. Lower concentrations of these same preservatives were less effective. Thimerosal (0.001% and 0.004%), sorbic acid (0.1%), potassium sorbate (0.13%), EDTA (0.1%), polyaminopropyl biguanide (0.00005%), and polyquaternium-1 (0.001%) were not effective as tested. However, thimerosal 0.004% when combined in solution with EDTA was effective. Preservatives were more effective when tested against axenically prepared organisms than when tested against co-cultured organisms.

The effect of currently available contact lens disinfection systems on Acanthamoeba castellanii and Acanthamoeba polyphaga

Contact lens disinfection systems were evaluated for their effectiveness in killing Acanthamoeba castellanii and Acanthamoeba polyphaga trophozoites and cysts. Amoebae were inoculated into commercially available contact lens cleaning and soaking solutions. At intervals varying from 30 minutes to 24 hours, solutions were filtered. The filters were removed and cultured for Acanthamoeba organisms. Striking differences were observed in the abilities of the different disinfecting solutions to kill the organisms. Solutions containing chlorhexidine were effective at very short exposure times. Solutions containing benzalkonium chloride required slightly longer exposure times but were faster than solutions containing only thimerosal. Solutions containing sorbate, polyaminopropyl biguanide, or polyquaternium-1 were not effective at killing Acanthamoeba organisms in the time allotted for the experiment. Solutions containing hydrogen peroxide were quite effective if the agent was not prematurely catalyzed. A. polyphaga generally required longer exposure to disinfectants than did A. castellanii for complete inhibition to occur.

Geographic origin and spread of pathogenic Naegleria fowleri deduced from restriction enzyme patterns of repeated DNA

The restriction enzyme patterns of repeated DNA from 20 Naegleria fowleri and 13 N. gruberi strains were compared. On this basis strains of N. fowleri could be easily separated from N. gruberi. Although the restriction enzyme profiles of N. fowleri strains are quite homogenous, strains originating from Europe and from Australia had slightly different patterns. Both European and Australian profiles were found in the USA. In Australia a genetic variant was detected that is the same as the N. fowleri type present in New Zealand. Profiles of strains from India were identical with those from Europe. These results give additional information on the probable origin and dispersal of N. fowleri in the world. Strains of N. gruberi exhibit much more heterogenous banding patterns. Four European N. gruberi strains were, however, nearly identical while two strains from New Zealand had only a single band difference with one restriction enzyme. One Australian strain of N. gruberi was identical to an American strain that has been in culture for almost 30 years. The presence of a virus-like particle in a sister strain of this American isolate did not affect its banding patterns. Other strains of N. gruberi from the USA had diverse restriction enzyme patterns. Adelphamoeba galeacystis has restriction enzyme profiles distinct from those of the Naegleria strains investigated. Isoenzyme analysis in agarose isoelectric focusing confirmed the existence of intraspecific differences in N. fowleri.

Primary amoebic meningoencephalitis in a young male from northwestern Mexico

Primary meningoencephalitis caused by Naegleria fowleri was documented in a 16-year-old male from Mexicali in the state of Baja California in Mexico. In August 1978, seven days after sustaining moderate head trauma while swimming in a shallow, stagnant irrigation ditch on a hot summer day, the patient presented an acute illness with severe headache, fever and convulsions rapidly progressing into a comatose state. Actively moving trophozoites were observed in the spinal fluid on admission. The patient died shortly after admission to hospital on the third day of symptoms. Post-mortem examination revealed a meningoencephalitis with extensive destruction, haemorrhage and numerous parasites involving structures of the posterior fossa. Immunoperoxidase strains of trophozoites in meningeal and cerebellar tissue were positive for N. fowleri KUL and negative for N. gruberi, N. australiensis and Acanthamoeba rhysodes. This appears to be the first documented case of the disease in Mexico.

Seasonal distribution of pathogenic free-living amebae in Oklahoma waters

Pathogenic free-living amebae cause serious human disease, including infection of the eye and the central nervous system. The purpose of this study was to sample aquatic environments in the Tulsa, Oklahoma, area year-round for the presence of these disease-causing amebae. A total of 34 pathogenic isolates were obtained from 2,016 processed water and swab samples. Pathogenicity was determined by the ability of amebae to cause death in mice after intranasal inoculation. Pathogenic amebae were isolated during every month of the year and were identified as Naegleria australiensis (38%), Acanthamoeba species (35%), N. fowleri (18%), and leptomyxid amebae (9%). Pathogenic leptomyxids have not previously been reported from the environment. The greatest percentage of recovery of pathogens occurred during the spring and autumn. The prevalence of pathogenic free-living amebae in the sampled waters was 1 pathogen/3.4 l water.