Elizabeth Ramirez

Removal of pathogens from wastewaters by the root zone method (RZM)

Full-scale and laboratory-scale artificially constructed reed beds utilising the root zone method (RZM) of wastewater treatment were investigated for their removal efficiencies of a range of pathogenic microorganisms. Performances were compared for RZMs employing different hydrophytes, planting substrates and climatic conditions. All pathogens were removed by the RZM to some extent. Planted beds generally performed better than unplanted beds although the type of hydrophyte used was not significant. Gravel beds were more efficient than soil beds in the removal of protozoan pathogens and of helminth eggs; numbers of these pathogens were below levels of detection in gravel bed effluents. For faecal coliforms the type of planting substrate was not significant, providing hydrophytes were present. Climatic conditions made little difference to treatment efficiency although seasonal variation was observed in temperature climates, where the removal of faecal coliforms declined in the winter months, and in subtropical climates where higher numbers of free-living amoebae were recorded during the summer. It was concluded that the RZM is a suitable method for the treatment of domestic wastewaters in tropical and subtropical regions of Mexico.

Amoebae isolated from the atmosphere of mexico city and environs

A protozoological analysis was performed from June to August, 1982 to isolate small free-living amoebae from the atmosphere by using an air vacuum sampler and several filters. Monoxenic medium (nonnutritive agar plus Escherichia coli) and axenic medium (De Jonckheere, 1977) were used to culture the isolates. The species isolated included Naegleria sp. Alexeieff emend. Calkins, Acanthamoeba polyphaga Puschkarew, Vahlkampfia jugosa Page, Acanthamoeba astronyxis Ray and Hayes, Acanthamoeba castellanii Douglas, Acanthamoeba culbertsoni Singh y Das, Vahlkampfia ustiana Page, Saccamoeba stagnicola Page, Hyalodiscus sp. Hertwig and Lesser, Platyamoeba placida Page, Rugipes sp. Schaeffer, Vannella platypodia Gläser, Vahlkampfia russelli Singh, Vahlkampfia ovis Schmidt, and Leptomyxa flabellata Goodey. Among the species isolated Naegleria sp., A. polyphaga, A. culbertsoni, and A. castellanii include strains, known to be pathogenic in humans.

Pathogenic Amoebae in Natural Thermal Waters of Three Resorts of Hidalgo, Mexico

In a search for free-living amoebae, seven water samples from three thermal water bathing resorts in Tecozautla, Hidalgo, were analyzed during December 1984. The samples were concentrated by filtration and centrifugation, and inoculated later on monoxenic and axenic media. The identification of the isolates was performed by morphology and isoelectric focusing of isoenzymes and total proteins. Thirty-three strains of free-living amoebae belonging to the genera Naegleria, Acanthamoeba, and Willaertia were isolated. Twenty of these strains belonged to the Naegleria genus, 16 of them were classified as Naegleria spp., and 2 were classified as Naegleria lovaniensis. Noteworthy was the finding of two pathogenic strains of the species Naegleria australiensis. N. australiensis and N. lovaniensis may be considered good indicator organisms, since they live in the same environmental conditions as N. fowleri, the agent of primary amoebic encephalitis (PAM). On the other hand, amoebae other than Naegleria were isolated and identified as Acathamoeba castellanii (two strains), and Acanthamoeba lugdunensis (one strain), which proved to be pathogenic when tested in mice. Nine more pathogenic strains of the genus Acanthamoeba spp. were isolated together with one strain of Willaertia magna, a thermophilic nonpathogenic amoeba. The chlorination and periodical surveillance of water resorts like the one studied is recommended, in order to prevent the appearance of more cases of PAM or other human diseases associated with pathogenic Acanthamoeba spp.

Seasonal distribution of air-borne pathogenic and free-living amoebae in Mexico City and its suburbs

A survey was carried out over a one-year period to isolate amoebae suspended in the air of Mexico City and its suburbs. Sampling stations were placed at the four cardinal points of the metropolitan area. Selective media were used to culture the amoebae isolated. Specialized taxonomic keys and physical and physiological tests were used for identification, and a statistical analysis was performed to determine the correlations between physico-chemical and biological parameters. 108 strains were isolated, of which 19 were pathogenic via intracerebral inoculation and 9 via intranasal inoculation. Species of the generaAcanthamoeba, Vahlkampfia andHartmannella were most abundant.Acanthamoeba polyphaga showed the highest abundance. Several times during the period of the study SO2 O3, CO, NO and NO2 exceeded the permissible levels established by the Mexican government. The ability of amoebae to form cysts and cyst size were important factors for their presence, survival, abundance and diversity in the atmosphere. The main source of air-borne amoebae was the soil. Factors that favored the incidence and diversity of the isolates were wind speed and direction, low relative humidity, generation of frequent dust-storms, resuspension of amoebae by vehicular traffic, proximity to garbage dumps and large extensions of bare soil. Soil cover was a factor associated with a reduction in the incidence and diversity of the aerial amoebae. This study demonstrates that there are viable cysts of amoebae in the atmosphere of Mexico City, that may have potential importance in the case of certain kinds of human allergies and diseases. Further research is needed to find out the aerial presence of viable cysts of obligatory, amphizoic or opportunistic amoebic parasites, and to clarify the qualitative and quantitative effects of the local meteorological and physico-chemical environment on the free-living amoebae present in the atmosphere.

SEASONAL DISTRIBUTION OF AIR-BORNE PROTOZOA IN MEXICO CITY AND ITS SUBURBS

A survey was carried out over a 1-yr period to isolate protozoa suspended in the air of Mexico City and its suburbs. Sampling stations were placed at four cardinal points of the metropolitan area. Selective media were used to culture the protozoa isolated. Specialized taxonomic keys were used for identification and a statistical analysis was performed to determine the correlations between physicochemical and biological parameters. 63 strains were isolated. Species of Kinetoplastida and Chrysomonadida were most abundant, namely species of the genera Bodo, Cercobodo, Monas and Helkesimastix. Amoeboflagellates found included Mastigamoeba and Tetramitus. The only ciliate isolated was Colpoda steini. The greatest number of strains was yielded by Bodo repens and Cercobodo radiatus. Several times during the period of the study SO2, O3, CO, NO, and NO2 exceeded the permissible levels established by the Mexican government. From the results of this study it was concluded that the ability of protozoa to form cysts and cyst size were important factors for their presence, survival, abundance and diversity in the atmosphere. The main source of air-borne protozoa was the soil. Factors that favored the incidence and diversity of the isolates were wind speed and direction, high relative humidity, generation of frequent dust-storms, resuspension of protozoa by vehicular traffic, proximity to garbage dumps and large extensions of bare soil, and temperature (the latter only when it did not favor the production of high levels of O3). Factors that were hostile to the aerial protozoa were industry and their contaminants, and high concentrations of O3 and SO2, especially in winter time when thermal inversions occurred. Soil cover was also associated with a reduction in the incidence and diversity of the aerial protozoa. This study demonstrates that there are viable cysts of protozoa in the atmosphere of Mexico City, that may have potential importance in the case of certain kinds of human allergies and diseases. Further research is needed to find out the aerial presence of viable cysts of obligatory, amphizoic or opportunistic protozoan parasites, and to clarify the qualitative and quantitative effects of the local meteorological and physico-chemical environment on the free-living protozoa present in the atmosphere.

Amoebae in a waste stabilization pond system in Mexico

A protozoological survey was performed to analyze the organisms of the subphylum Sarcodina Schmarda, present in waste stabilization ponds located at Santo Tomás Atzingo, México, from March to December 1981. The amoebae isolated were identified and counted. Several physicochemical parameters were also determined and correlated with the biological data.Thirteen amoebic species were isolated and identified: one definite pathogen, Entamoeba histolytica Schaudinn; three species that have shown pathogenic strains for humans: Acanthamoeba polyphaga Page, Acanthamoeba castellanii Douglas, and Naegleria sp. (Alexeieff) Calkins; two opportunist species: Entamoeba coli (Grassi) Casagrandi and Barbagallo, and Iodamoeba bühschlii (Von Prowazek) Dobell; and seven free-living amoebae: Acanthamoeba astronyxis Ray and Hayes, Amoeba proteus (Pallas) Leidy, Hartmannella exundans Page, Hartmannella vermiformis Page, Pelomyxa palustris Leidy, Vahlkampfia avara Page, and Vahlkampfia russelli Singh.A clear correlation between the number of amoebae and the temperature and alkalinity of the system was found. The removal capacity of the ponds for E. histolytica varied from 30 to 100% during the survey. The amoebae showed a succession in space and time in the system studied.

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.

AN INVESTIGATION OF THE PATHOGENIC AND NON­ PATHOGENIC FREE-LIVING AMOEBAE FROM THE ROOT ZONE METHOD OF WASTEWATER TREATMENT

Pathogenic and non-pathogenic free-living amoebae from the Root Zone Method (RZM) of wastewater treatment were investigated. Ten reed beds planted on four different substrate types were compared for their efficiency of removal of free-living amoebae. Reed beds planted on coarse substrates generally gave the highest removal rates (up to 100%) while those planted in soil gave the lowest (60.4%). Possible reasons for differences in removal efficiencies are discussed. Thirteen species representing nine genera of free-living amoebae were isolated; these included three species of Acanthamoeba (A. astronyxis, A. polyphaga and A.rhysodes) all of which were pathogenic for mice. The implications for RZM design of the presence of potentially pathogenic free-living amoebae in the effluent are discussed.

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).