Isolation and Identification of Naegleria Species in Irrigation Channels for Recreational Use in Mexicali Valley, Mexico

Multiplex Real-Time Polymerase Chain Reaction Assay To Detect Acanthamoeba spp., Vermamoeba vermiformis, Naegleria fowleri, and Balamuthia mandrillaris in Different Water Sources

Free-living amoebae (FLA) are widely distributed in the environment. Among these, Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris, and Vermamoeba vermiformis have been reported as human pathogens with health effects ranging from lethal encephalitis to different epithelial disorders. Despite this, FLA still present many diagnostic challenges. The aim of this study was to develop a rapid and efficient multiplex real-time quantitative polymerase chain reaction (qPCR) to simultaneously detect Acanthamoeba spp., N. fowleri, B. mandrillaris, and V. vermiformis in different water sources. For the validation of the qPCR assay, 38 samples (19 tap water and 19 stagnant water sources) were analyzed. The qPCR assay accurately identified the four types of FLA with no cross-reactivity. Considering water samples with results subsequently confirmed by conventional PCR, the multiplex qPCR assay detected 18/38 (47.4%) positive samples (Acanthamoeba spp. in 44.7% and V. vermiformis in 31.6%) and growth in nonnutritive agar (NNA) cultures identified 7/38 (18.4%) positive samples. Of the tap water samples analyzed, 26.3% of samples positive for FLA were detected by growth in NNA culture whereas 31.6% were identified by qPCR. In addition, FLA were detected in 2/19 stagnant water samples (10.5%) by growth in NNA culture and in 12/19 stagnant water samples (63.2%) by qPCR. Neither N. fowleri nor B. mandrillaris was detected in the water samples analyzed. In conclusion, the qPCR developed showed its potential as a rapid tool for detection of Acanthamoeba spp., N. fowleri, B. mandrillaris, and V. vermiformis. Moreover, FLA species were detected in half of the water sources evaluated, suggesting the importance of the surveillance of these potential infectious agents.

Saline-Tolerant Pathogenic Acanthamoeba spp. Isolated from a Geothermal Power Plant

Few studies have been conducted in the cooling systems of power plants; they have focused on Naegleria fowleri, leaving a gap in the knowledge of other pathogenic free-living amoebae in this environment. The objective of this study was to determine the occurrence of saline-tolerant pathogenic Acanthamoeba in a geothermal power plant. The identification of isolated amoebae at genus level was carried out, observing their morphological characteristics; the determination of genotype and species of Acanthamoeba was performed via molecular biology (PCR). Water temperature ranged from 18 to 43 °C and conductivity from 4.0 × 104 to 8.7 × 104 μS/cm; this last value was greater than the seawater value. Only five amoeba genera were found. Acanthamoeba was in all the sampling sites, showing high saline tolerance. The high temperature, but mainly high conductivity, were the environmental conditions that determined the presence of pathogenic free-living amoebae in the hot water. All the strains of Acanthamoeba culbertsoni killed the mice, having a mortality of 40 to 100%. Acanthamoeba genotypes T10 and T5 were identified, T10 is rarely isolated from the environment, while T5 is more frequent. This is the first time that genotypes T5 and T10 have been reported in the environment in Mexico.

Naegleria fowleri outbreak in Pakistan: unveiling the crisis and path to recovery

The outbreak of Naegleria fowleri in Pakistan presents a significant public health concern due to its high fatality rate and limited treatment options. This review explores the impact of the outbreak on communities and the challenges faced in combating the disease. It evaluates available treatment options and highlights the need for early diagnosis and intervention. The study proposes recommendations to improve public health preparedness, including public awareness campaigns, enhanced healthcare infrastructure, and robust water surveillance systems. Collaboration between research institutions and public health organizations is emphasized to develop effective outbreak response strategies.

Two MP2CL5 Antigen Vaccines from Naegleria fowleri Stimulate the Immune Response against Meningitis in the BALB/c Model

Naegleria fowleri is an etiological agent that generates primary amoebic meningoencephalitis; unfortunately, no effective treatment or vaccine is available. The objective of this work was to determine the immunoprotective response of two vaccine antigens, as follows: (i) the polypeptide band of 19 kDa or (ii) a predicted immunogenic peptide from the membrane protein MP2CL5 (Smp145). Both antigens were administered intranasally in mice using cholera toxin (CT) as an adjuvant. The survival rate and immune response of immunized mice with both antigens and challenged with N. fowleri trophozoites were measured in the nose-associated lymphoid tissue (NALT) and nasal passages (NPs) by flow cytometry and enzyme-linked immunosorbent assay (ELISA). We also determined the immunolocalization of both antigens in N. fowleri trophozoites by confocal microscopy. Immunization with the polypeptide band of 19 kDa alone or coadministered with CT was able to confer 80% and 100% of protection, respectively. The immunization with both antigens (alone or coadministered with CT) showed an increase in T and B lymphocytes. In addition, there was an increase in the expression of integrin α4β1 and IgA in the nasal cavity of protected mice, and the IgA, IgG, and IgM levels were increased in serum and nasal washes. The immunolocalization of both antigens in N. fowleri trophozoites was observed in the plasma membrane, specifically in pseudopod-like structures. The MP2CL5 antigens evaluated in this work were capable of conferring protection which would lead us to consider them as potential candidates for vaccines against meningitis caused by N. fowleri.

Extensive Cryptic Diversity and Ecological Associations Uncovered among Mexican and Global Collections of Naegleria and Vermamoeba Species by 18S Ribosomal DNA, Internal Transcribed Spacer, and Cytochrome Oxidase Subunit I Sequence Analysis

Free-living amoebae (FLA) are phagocytic protists that play crucial roles in microbial communities as significant microbial grazers. However, our current knowledge of their diversity, ecology, and population genetic structures is marginal due to the shallow and biased sampling of ecosystems and the use of few, poorly resolving molecular markers. Thirty-two FLA were isolated from soil and water samples collected across representative ecosystems of the State of Morelos in Central Mexico, including the drinking water distribution system (DWDS) from the state capital. We classified our isolates as members of Acanthamoeba, Vermamoeba, Naegleria, and Tetramitus by 18S ribosomal DNA (rDNA) sequencing. Vermamoeba isolates were recovered exclusively from the DWDS samples. In contrast, Naegleria strains displayed a broad distribution in soil and water samples across the natural ecosystems. We used a combination of phylogenetic and population genetic analyses of internal transcribed spacer (ITS) and cytochrome oxidase subunit I (COI) sequences from our isolates and a comprehensive set of reference sequences to analyze the currently known diversity of Naegleria spp. Significant associations were uncovered between the most prevalent lineages of Naegleria and Vermamoeba and broad ecological and geographical variables at regional and global levels. The population structure and cryptic diversity within the Naegleria galeacystis-Naegleria americana and Vermamoeba vermiformis species complexes were thoroughly analyzed. Our results prove that the genus Vermamoeba, which was previously thought to consist of only one species, actually encompasses at least seven widely distributed species, as indicated by consistent evidence from Bayesian phylogenetics, two species-delimitation programs, and population genetics analyses. IMPORTANCE Our study sheds new light on the population genetic structure of V. vermiformis and diverse Naegleria species. Using improved molecular markers and advanced analytical approaches, we discovered that N. americana, previously considered a single species, actually contains multiple distinct lineages, as revealed by COI sequencing. These lineages are highly differentiated, with little gene flow between them. Our findings demonstrate that the genus Vermamoeba holds multiple cryptic species, requiring a significant taxonomic revision in light of multilocus sequence analyses. These results advance our understanding of the ecology, molecular systematics, and biogeography of these genera and species complexes at both regional and global scales. This study has significant implications for diagnosing amoebal infections and evaluating health risks associated with FLA in domestic and recreational waters.

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.

Primary Amoebic Meningoencephalitis by Naegleria fowleri: Pathogenesis and Treatments

Naegleria fowleri is a free-living amoeba (FLA) that is commonly known as the "brain-eating amoeba." This parasite can invade the central nervous system (CNS), causing an acute and fulminating infection known as primary amoebic meningoencephalitis (PAM). Even though PAM is characterized by low morbidity, it has shown a mortality rate of 98%, usually causing death in less than two weeks after the initial exposure. This review summarizes the most recent information about N. fowleri, its pathogenic molecular mechanisms, and the neuropathological processes implicated. Additionally, this review includes the main therapeutic strategies described in case reports and preclinical studies, including the possible use of immunomodulatory agents to decrease neurological damage.