Esperanza Robles

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

A survey of pathogenic and free-living amoebae in swimming pool waters of Mexico City was performed. Among the organisms isolated those which have public health importance were Naegleria fowleri Carter and Acanthamoeba castellanii Douglas. Amoebae of the genera Acanthamoeba, Naegleria, and Vahlkampfia were recovered in their cystic stage while those specimens of the genera Amoeba, Entamoeba, Thecamoeba, and Vanella were recovered only in their trophic stage during this study. Amoebae were concentrated through filtration procedures and subsequently cultured in different culture media. Nonpathogenic amoebae also isolated by culture included: Amoeba proteus (Pallas) Leidy, Amoeba striata Penard, Paratetramitus jugosus Page, Acanthamoeba astronyxis Ray and Hayes, Vahlkampfia avara Page, Vahlkampfia inornata Page, Thecamoeba verrucosa Ehrenberg, and Vanella mira Schaeffer. Trophozoites of Entamoeba gingivalis Gros, were also recovered, both directly and by culture. Most commonly found were amoebae of the species Naegleria gruberi Schardinger (59.02%), N. fowleri (16.77%), and A. castellanii (7.64%). Least-frequently found amoebae belonged to the species Thecamoeba verrucosa (0.12%). All isolated strains of N. fowleri and A. castellanii were thermophilic at 45 and 40 degrees C, respectively, and also pathogenic when inoculated into white mice. More populated by amoebae were those swimming pools of the indoor type with an inner side garden. It was also shown that the free residual chloride values of 0.50 to 1.5 mg/liter, ordinarily used in pool waters, are not adequate for elimination of amoebae.

Bottled-Water Quality in Metropolitan Mexico City

Bacteriological and physico-chemical parameters of 265 samples from 39 brands sold in 5-gallon plastic and glass bottles and 2-5 L plastic containers were analyzed to determine the quality of bottled water distributed in Mexico City. Tests included fecal and total coliform counts, alkalinity, total hardness, chloride, calcium and magnesium concentrations, pH and conductivity. Correlation and cluster analyses and ANOVA were carried out, and a comparison made of the averages with the maximum permissible levels established in the Official Mexican Norms. Concerning the investigated parameters no differences (p > 0.05) between the brands were found. Physico-chemical parameters were studied and all the samples were within the permissible limits. Most samples taken from the 5-gallon containers exceeded the maximum bacteriological limits. It was concluded that the bacteriological quality of the brands studied was extremely variable. Appropriate sanitary measures, should be established to control this aspect.

Distribution of free-living amoebae in a treatment system of textile industrial wastewater

Free-living amoebae have been found in soil, air and a variety of aquatic environments, but few studies have been conducted on industrial wastewater and none on wastewater from the textile industry. The aim of this study was to determine the presence and distribution of free-living amoebae in a biological treatment system that treats textile industrial wastewater. Samples were taken from input, aeration tank, sedimentation tank and output. Samples were centrifuged at 1200g for 15min, the sediment was seeded on non-nutritive agar with Enterobacter aerogenes (NNE) and the plates were incubated at 30 and 37°C. Free-living amoebae were present in all stages of the treatment system. The highest number of amoebic isolates was found in the aeration tank and no seasonal distribution was observed during the year. A total of 14 amoeba genera were isolated: Acanthamoeba, Echinamoeba, Korotnevella, Mayorella, Naegleria, Platyamoeba, Saccamoeba, Stachyamoeba, Thecamoeba, Vahlkampfia, Vannella, Vermamoeba, Vexillifera and Willaertia. The most frequently found amoebae were Acanthamoeba and Vermamoeba which were found in all treatment system stages. The constant presence and diversity of free-living amoebae in the treatment system were important findings due to the characteristics of the wastewater from the textile plant in terms of the residue content from colorants, fixers, carriers, surfactants, etc., used in fabric dyeing and finishing processes. The factors that determined the presence and distribution of amoebae in the activated sludge system were their capacity to form cysts, which allowed them to resist adverse conditions; food availability; an average temperature of 27-33°C; dissolved oxygen in average concentrations above 2mg/L, and pH in a range of 5.9-7.1.

Free-living amoebae isolated from water-hyacinth root (Eichhornia crassipes)

Free-living amoebae are widely distributed in aquatic environments and their hygienic, medical and ecological relationships to man are increasingly important. The purpose of this study was to isolate free-living amoebae from water-hyacinth root (Eichhornia crassipes) and the water of an urban lake in Mexico City. Five grams of wet root were seeded on non-nutritive agar with Enterobacter aerogenes (NNE). Water samples were concentrated by centrifugation at 1200g for 15min and the pellet was seeded on NNE. Of the 16 isolated genera, 10 were detected in both habitats. The most frequent were Vannella in root and Acanthamoeba and Naegleria in water. The total number of isolates and genera isolated from root was higher than that isolated from water. The differences between root and water are probably due to the morphological characteristics of water-hyacinth root, which provides a large habitat and refuge area for many organisms.

Acanthamoeba Isolated from Contaminated Groundwater

FREE-LIVING amoebae (FLA) can cause brain infection in humans and other animals, which in the majority of cases leads to death. Pathogenic species include the genera Naegleria, Acanthamoeba, Balamuthia, and Sappinia. They are widespread in nature, and have been detected in several types of water systems (Bonilla and Ramirez 2004; Ramı́rez and Bonilla 1995; Ramirez et al. 2005; Schuster and Visvesvara 2004), but groundwater protozoa have remained virtually unstudied. However, it is now known that protozoa are probably present in groundwater. In pristine aquifers their numbers may be low or even zero whereas in organically contaminated aquifers the abundance of protozoa is usually much higher (Bitton and Gerba 1984). This is probably the result of high growth rates of bacteria, which support larger populations of protozoa that feed on bacteria (Chapelle 1993). The aims of study were: to analyze organically contaminated groundwater for the presence of Acanthamoeba, to test their pathogenecity, and to relate their presence with some environmental conditions. The aquifer of Mezquital Valley was selected to carry out the research, because this area is an old, large-scale scheme for agricultural irrigation using urban wastewater. The Mezquital Valley is located in the State of Hidalgo about 50 km north of Mexico City. Rainfall in this area is largely restricted to a well-defined wet season lasting from May to September. Currently, about 45,000 ha of semiarid land is irrigated with urban wastewater, mostly from Mexico City. The principal agricultural crops are cereals and vegetables of various types. About 10,000 ha receive raw wastewater directly and another 35,000 ha are irrigated with a mixture of wastewater (80%) and dam-stored fluvial water (20%). Most of this wastewater receives a form of primary treatment (Siebe and Cifuentes 1995).

Microbiological and Physicochemical Quality of Well Water Used as a Source of Public Supply

The sources of microbial and chemical contamination of groundwater are numerous and have severe implications for public health. The objective was to determine the microbiological and physicochemical quality of wells in the west and east of the Cuautla-Yautepec aquifer in Mexico. Wells showed bacteriological contamination in at least one sampling. Coliform values were lower than the maximum permissible limit indicated in the Mexican Ecological Criteria of Water Quality (1000 colony forming unit (CFU)/100 ml of fecal coliforms) for supply sources. The number of isolated amoebae was low, but these were present all year round. Amoebae were found in 71.7% of the samples and belonged to 13 genera. The most frequent amoeba, Hartmannella, occurring in 44% of the samples, has been associated with eye and brain infection, but its role as a cause of infection has not been confirmed. A gradient was observed for dissolved solids according to altitude; the concentrations of dissolved solids increased in wells with lower altitudes. Total hardness values were above 180 mg/L CaCO3, therefore the water is considered very hard, and both carbonate and non-carbonate hardness was detected. The average values of physicochemical parameters were below the maximum permissible limits indicated in the Mexican official norm.

A comparison between the spatial distribution pattern of flagellates and some physicochemical parameters in a waste stabilization pond

Protozoological and physicochemical analyses were performed in a waste stabilization pond at Sto. Tomas Atzingo, a small town near Mexico City, in order to discern the internal dynamics of the pond water through the study of the spatial distribution pattern of flagellates and the parallel water volume distribution pattern of some selected physicochemical determined parameters. The statistical method applied to the data obtained was by cluster analysis. The results showed a slight trend to heterogeneity in the system, when it was evaluated through the physicochemically determined parameters. On the other hand, the spatial distribution pattern of the flagellates pointed out a remarkable heterogeneity in the pond. In systems like the one studied where the main feature is an organic matter overload, such a difference in findings indicates a low correlation between the biological parameters, in this case the flagellates, and the physicochemical variables, that should be considered when evaluating the water quality of such systems, either through the physicochemical, the biological or both scopes.