Fermin Rivera

Pathogenic and Free-Living Protozoa Cultured from the Nasopharyngeal and Oral Regions of Dental Patients

Protozoa of the nose, mouth, and pharynx of 30 randomly chosen male caries patients at an odontological clinic of the National Autonomous University of Mexico, in Mexico City, were surveyed by culture from swabs. Culture tubes from swabs were observed every other day for 5 weeks. Pathogens found included Entamoeba histolytica, Naegleria fowleri, Acanthamoeba castellanii, A. culbertsoni, A. polyphaga, and Giardia lamblia. Such isolations of pathogens suggest that patients may be healthy carriers of cysts and trophic forms of protozoa responsible for several human diseases. Amoebae responsible for primary amoebic meningoencephalitis were well represented in the samples. Small pathogenic free-living amoebae have not been isolated before from healthy males in Mexico. Many species of free-living cyst-forming protozoa and some commensals without cysts were also cultured from swabs.

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.

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.

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.

Zooflagellates in an anaerobic waste stabilization pond system in Mexico

A protozoological survey was performed on waste stabilization lagoons to isolate, identify, and determine the incidence of zooflagellates present in these waters. A correlation between the species found and the physicochemical parameters determined was also done. Fifteen samplings were analyzed from June 1981 to April 1982. Free-living zooflagellates included: Bodo edax Klebs: Bodo caudatus Dujardin;Trepomonas agilis Dujardin;Pleuromonas jaculans Perty (all of them polisaprobic indicators);Bodo saltans Ehrenberg (a mesosaprobic indicator); and Bodomorpha minima Hollande. A human commensal species Enteromonas hominis Da — Fonseca, was also isolated. The performance of the lagoons was predominantly anaerobic. The temperature seemed to be the most influential factor on the incidence of the zooflagellates isolated, especially in winter time.

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.

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.