Efficiency of wastewater treatment plants at removing Giardia sp. cysts in southern France.

A study was conducted to evaluate the removal efficiency for Giardia sp. cysts of a number of wastewater treatment plants in France. Of these, five were activated sludge systems, three were trickling filters and three were waste stabilisation pond systems.

Physiological changes of Salmonella typhimurium cells under osmotic and starvation conditions by image analysis.

The effects of starvation and salinity on the physiology of Salmonella typhimurium were investigated in a microcosm study. The physiological changes were monitored by using fluorochromes dyes such as DAPI (4',6-diamidino-2-phenylindole) for evaluation of the genomic content, CTC (5-cyano-2,3-ditolyl tetrazolium chloride) for respiratory activity and syto 9 and propidium iodide for cytoplasmic membrane damages. The metabolic activity of the cellular population was assessed with the method of Kogure (direct viable count), to enumerate the substrate-responsive cells.

Viability and virulence of experimentally stressed nonculturable Salmonella typhimurium.

Maintenance of pathogenicity of viable but nonculturable Salmonella typhimurium cells experimentally stressed with UV-C and seawater, was investigated relative to the viability level of the cellular population. Pathogenicity, tested in a mouse model, was lost concomitantly with culturability, whereas cell viability remained undamaged, as determined by respiratory activity and cytoplasmic membrane and genomic integrities.

Recombinant plasmid mobilization between E. coli strains in seven sterile microcosms.

Transfer by mobilization of a pBR derivative recombinant plasmid lacking transfer functions (oriT+, tra-, mob-) from one E. coli K12 strain to another was investigated in seven sterile microcosms corresponding to different environments. These microcosms were chosen as representative of environments that genetically engineered microorganisms (GEMOs) encounter after accidental release, namely attached biomass in aquatic environments (biofilm), soil, seawater, freshwater, wastewater, mouse gut, and mussel gut, GEMOs survived in the same way as the host strains in all microcosms.

[Survival of Bulinus truncatus and Biomphalaria pfeifferi in sewer water purified in stabilization ponds in a sudanese-saharan zone].

In subsaharan Africa wastewater purification to protect the health of the population could create stagnate water reservoirs for parasitic vectors such as snails which are intermediate hosts of bilharzia. Laboratory studies of the survival of Bulinus truncatus, an intermediate host of Schistosoma haematobium, and Biomphalaria pfeifferi, an intermediate host of Schistosoma mansoni, in waste water purified in stabilization ponds showed that Biomphalaria pfeifferi thrives to dirty water (60 mg/l < or = COD < or = 1060 mg/l) while Bulinus truncatus survived only in slightly cleaner water (60 mg/l < or = COD < or = 200 mg/l). Field studies showed that Biomphalaria pfeifferi disappeared after 48 hours as compared to 25 days in the laboratory.

Dynamics of non-O1 Vibrio cholerae and fecal coliforms in experimental stabilization ponds in the arid region of Marrakesh, Morocco, and the effect of pH, temperature, and sunlight on their experimental survival.

We studied the spatial-temporal dynamics of non-O1 Vibrio cholerae numbers at a stabilization pond treatment plant. This bacterium's seasonal dynamics were the inverse of those of fecal coliforms, with high levels in hot periods and low levels in cold periods. Stabilization pond treatment did not significantly reduce non-O1 V.

Effects of environmental factors present in the St. Lawrence Estuary (Quebec, Canada) on experimental survival of Salmonella salamae as determined by flow cytometry.

Survival of Salmonella salamae in the St. Lawrence Estuary was studied experimentally during an oceanographic cruise using in situ exposure diffusion chambers. The abundance distribution (colony-forming units) of culturable S.

Effects of pili rigidity and energy availability on conjugative plasmid transfer in aquatic environments.

Conjugal transfer frequencies of nonconjugative plasmid pCE325 associated with either the conjugative plasmid R388 (rigid pili) or R100-1 (flexible pili) were measured in waste water and seawater between two strains of Escherichia coli K12. These strains were selected from three strains after estimating (i) their survival capacity in the two water types and (ii) the maintenance and expression of plasmid-located genes in the different strains. Mobilization of plasmid pCE325 was always below the detection limit, but increased when organic matter was added to the microcosms.

Comparison of flow cytometry and epifluorescence microscopy for counting bacteria in aquatic ecosystems.

Flow cytometry was used to count bacterial cells from diverse origins: one strain of E. coli, one sample of lake water, and 18 samples of estuary water. To verify the accuracy and the precision of this technique, total bacteria counts made by flow cytometry were compared with counts by direct observation using epifluorescence microscopy.

Aeromonas species in stabilization ponds in the arid region of Marrakesh, Morocco, and relation to fecal-pollution and climatic factors.

During the period 12 July 1985 to 23 December 1987, water samples were collected in two-week intervals for estimates ofAeromonas species in a waste treatment system located in the arid region of Marrakech, Morocco. Fecal coliforms, temperature, and chemical oxygen demand were measured simultaneously withAeromonas species densities. Statistical methods were utilized to analyze the significance of average differences and temporal patterns ofAeromonas species numbers.

Distribution and survival of motile Aeromonas spp. in brackish water receiving sewage treatment effluent.

The spatiotemporal distributions of Aeromonas spp. and fecal coliforms in a cove receiving sewage treatment effluent and draining into a brackish lagoon were studied for 34 months with sampling at six stations. A total of 452 strains of Aeromonas spp.

Haemolysin occurrence among Aeromonas hydrophila, Aeromonas caviae and Aeromonas sobria strains isolated from different aquatic ecosystems.

A total of 909 Aeromonas spp. isolates from different aquatic ecosystems were tested for haemolysin production by both sheep and horse blood agar-plate assays and by rabbit erythrocytes in broth assay. A comparison of these different methods was undertaken in order to appreciate their capacity to evaluate the haemolytic activity of Aeromonas spp.

Dynamics of Aeromonas hydrophila, Aeromonas sobria, and Aeromonas caviae in a sewage treatment pond.

The spatiotemporal dynamics of Aeromonas spp. and fecal coliforms in the sewage treatment ponds of an urban wastewater center were studied after 20 months of sampling from five stations in these ponds. Isolation and identification of 247 Aeromonas strains were undertaken over four seasons at the inflow and outflow of this pond system.

[Evaluation of microbial indicators of health risk related to river swimming places].

A retrospective follow-up study was conducted among 5,737 tourists in 8 holiday camps, during the 1986 summer, in the Ardèche river basin, in order to study the relationship between the bacteriological water quality and the morbidity that occurred to swimmers. Total morbidity was more frequent among bathers than non-bathers (Risk Ratio = 1.7 [95% confidence interval = 1.

Epidemiological significance of microbiological pollution criteria for river recreational waters.

A retrospective follow-up study was conducted during the summer of 1986 in the French Ardèche basin in order to assess the relationship between swimming-related morbidity and the bacteriological quality of the recreational water. 5737 tourists in eight holiday camps were questioned as to the occurrence of illness and their bathing habits during the week preceding the interviews. The rate-ratio contrasting swimmers and non-swimmers for total morbidity is 2.

[Evaluation of 2 culture media for the isolation and enumeration of motile Aeromonas in different kinds of water].

In recent years an increasing incidence of Aeromonas-related cutaneous infections and gastroenteritis has raised a serious public health problem. It appeared therefore timely to define a specific method allowing the rapid isolation and enumeration of the bacteria in their various aquatic habitats. In this line of research we have compared the growth of Aeromonas originating from different aquatic sources and raised on two media, i.

[Use of a new selective culture medium for isolation of Staphylococcus aureus in different types of water].

Different mediums actually available for recovering Staphylococcus aureus are not adapted for water analysis because of their low selectivity. This Note propose a new medium using Baird Parker agar medium additionned with sodium azide and incubated at 37 degrees C during 24 hrs. Three kinds of waters are tested: the efficiency of this medium is higher for surface waters using a modified technic of filtration.

Modeling of the evolution of bacterial densities in an eutrophic ecosystem (sewage lagoons).

The process of wastewater treatment was studied by modeling the relationships between physical, chemical, and biological (bacteria, phytoplankton, zooplankton) components of the sewage treatment lagoons of an urban wastewater center, based upon a two-year sampling program. The models of interactions between variables were tested by path analysis. The path coefficients were computed from the results of ridge regression, instead of linear multiple regression.

Dynamics of pollution-indicator and heterotrophic bacteria in sewage treatment lagoons.

The spatio-temporal dynamics of pollution-indicator bacteria and aerobic heterotrophic bacteria were studied in the sewage treatment lagoons of an urban wastewater center after 26 months of biweekly sampling at eight stations in these lagoons. Robust statistical methods of time-series analysis were used to study successional steps (through chronological clustering) and rhythmic behavior through time (through contingency periodogram). The aerobic heterotrophic bacterial community showed two types of temporal evolution: in the first four stations, it seems mainly controlled by the nutrient support capacity of the sewage input, whereas in the remaining part of the lagoon, it seems likely that the pollution-indicator bacteria are gradually replaced by other bacterial types that are better adapted to this environment.

A computer study of the evolution of aerobic heterotrophic bacterial populations in sewage and river waters.

The biodegradation of six surface active agents tested. The biochemical characteristics of the aerobic heterotrophic bacteria present in Montpellier waste waters and in Rhône water, before and after degradation, were studied by a standardized microbiological method. Four hundred strains isolated from these populations were compared to 29 reference strains by computer analysis.