Estelle Russek-Cohen

Reduction of cholera in Bangladeshi villages by simple filtration

Based on results of ecological studies demonstrating that Vibrio cholerae, the etiological agent of epidemic cholera, is commensal to zooplankton, notably copepods, a simple filtration procedure was developed whereby zooplankton, most phytoplankton, and particulates >20 μm were removed from water before use. Effective deployment of this filtration procedure, from September 1999 through July 2002 in 65 villages of rural Bangladesh, of which the total population for the entire study comprised ≈133,000 individuals, yielded a 48% reduction in cholera (P < 0.005) compared with the control.

Predictability of Vibrio cholerae in Chesapeake Bay

ABSTRACT Vibrio cholerae is autochthonous to natural waters and can pose a health risk when it is consumed via untreated water or contaminated shellfish. The correlation between the occurrence of V. cholerae in Chesapeake Bay and environmental factors was investigated over a 3-year period. Water and plankton samples were collected monthly from five shore sampling sites in northern Chesapeake Bay (January 1998 to February 2000) and from research cruise stations on a north-south transect (summers of 1999 and 2000). Enrichment was used to detect culturable V. cholerae, and 21.1% (n = 427) of the samples were positive. As determined by serology tests, the isolates, did not belong to serogroup O1 or O139 associated with cholera epidemics. A direct fluorescent-antibody assay was used to detect V. cholerae O1, and 23.8% (n = 412) of the samples were positive. V. cholerae was more frequently detected during the warmer months and in northern Chesapeake Bay, where the salinity is lower. Statistical models successfully predicted the presence of V. cholerae as a function of water temperature and salinity. Temperatures above 19°C and salinities between 2 and 14 ppt yielded at least a fourfold increase in the number of detectable V. cholerae. The results suggest that salinity variation in Chesapeake Bay or other parameters associated with Susquehanna River inflow contribute to the variability in the occurrence of V. cholerae and that salinity is a useful indicator. Under scenarios of global climate change, increased climate variability, accompanied by higher stream flow rates and warmer temperatures, could favor conditions that increase the occurrence of V. cholerae in Chesapeake Bay.

Physiological response curve analysis using nonlinear mixed models

Abstract. Nonlinear response curves are often used to model the physiological responses of plants. These models are preferable to polynomials because the coefficients fit to the curves have biological meaning. The response curves are often generated by repeated measurements on one subject, over a range of values for the environmental variable of interest. However, the typical analysis of differences in coefficients between experimental groups does not include a repeated measures approach. This may lead to inappropriate estimation of error terms. Here, we show how to combine mixed model analysis, available in SAS, that allows for repeated observations on the same experimental unit, with nonlinear response curves. We illustrate the use of this nonlinear mixed model with a study in which two plant species were grown under contrasting light environments. We recorded light levels and net photosynthetic response on anywhere from 8 to 10 points per plant and fit a Mitscherlich model in which each plant has its own coefficients. The coefficients for the photosynthetic light-response curve for each plant were assumed to follow a multivariate normal distribution in which the mean was determined by the treatment. The approach yielded biologically relevant coefficients and unbiased standard error estimates for multiple treatment comparisons.

Temperature-Driven Campylobacter Seasonality in England and Wales

ABSTRACT Campylobacter incidence in England and Wales between 1990 and 1999 was examined in conjunction with weather conditions. Over the 10-year interval, the average annual rate was determined to be 78.4 ± 15.0 cases per 100,000, with an upward trend. Rates were higher in males than in females, regardless of age, and highest in children less than 5 years old. Major regional differences were detected, with the highest rates in Wales and the southwest and the lowest in the southeast. The disease displayed a seasonal pattern, and increased campylobacter rates were found to be correlated with temperature. The most marked seasonal effect was observed for children under the age of 5. The seasonal pattern of campylobacter infections indicated a linkage with environmental factors rather than food sources. Therefore, public health interventions should not be restricted to food-borne approaches, and the epidemiology of the seasonal peak in human campylobacter infections may best be understood through studies in young children.

Direct Detection of Vibrio cholerae and ctxA in Peruvian Coastal Water and Plankton by PCR

ABSTRACT Seawater and plankton samples were collected over a period of 17 months from November 1998 to March 2000 along the coast of Peru. Total DNA was extracted from water and from plankton grouped by size into two fractions (64 μm to 202 μm and >202 μm). All samples were assayed for Vibrio cholerae, V. cholerae O1, V. cholerae O139, and ctxA by PCR. Of 50 samples collected and tested, 33 (66.0%) were positive for V. cholerae in at least one of the three fractions. Of these, 62.5% (n = 32) contained V. cholerae O1; ctxA was detected in 25% (n = 20) of the V. cholerae O1-positive samples. None were positive for V. cholerae O139. Thus, PCR was successfully employed in detecting toxigenic V. cholerae directly in seawater and plankton samples and provides evidence for an environmental reservoir for this pathogen in Peruvian coastal waters.

Analysis of fungal communities by sole carbon source utilization profiles.

A simple method for characterization of fungal communities in environmental samples was developed. Dilute suspensions of samples in 0.2% agar containing three different antibiotics were pipetted into 96-well plates (Biolog SF-N) containing a diverse collection of 95 different carbon sources. The plates were incubated for 4-12 days at 22 degrees C and the absorbance measured at 650 nm. Canonical variates analysis was then used to analyze the multivariate data. This method allowed fungal communities in rhizosphere soil of corn and soybean to be distinguished according to soil and plant type. Data taken at a single time-point, which varied greatly in total absorbance of the plate, separated rhizosphere samples primarily by soil type. When multiple time-points were combined to keep the total absorbance constant, differences in substrate utilization patterns due to different plant types could be distinguished. The method was also applicable to analysis of phylloplane and compost fungal communities. This method is readily applied to large numbers of samples and should be useful for community analysis in a variety of agricultural and ecological studies.

Use of the Transtheoretical Model of Change to Successfully Predict Fruit and Vegetable Consumption

Abstract This study examined the applicability of the transtheoretical model of change to assess readiness to increase fruit and vegetable intake in a nationally representative sample of U.S. adults. Using data from the 1991 5 A Day baseline survey of 2811 respondents, this study developed an algorithm based in part on responses to fruit and vegetable questions for classifying people into alternative stages of change. Associations were examined between stages of change, fruit and vegetable intake, and demographic and psychosocial factors. Results indicated that individuals can be classified by stage of change vis a vis fruit and vegetable intake. Persons in the higher stages of maintenance reported intakes that met national dietary recommendations of five or more servings of fruit and vegetables daily and those in action reported intakes that approached this level. Regression analyses showed that stages of change were a significant predictor of fruit and vegetable consumption, explaining 17% of the variation in fruit and vegetable intake. Stages of change and knowing the number of fruit and vegetable servings one should eat for good health provided the most parsimonious model, explaining 25% of the variance in total fruit and vegetable intake, compared with 29% for the full model.These findings suggest that stages are a successful predictor of fruit and vegetable consumption and implies a utility for the transtheoretical theory in the design and evaluation of stage-based nutrition messages for chronic disease prevention.

Genomic profiles of clinical and environmental isolates of Vibrio cholerae O1 in cholera-endemic areas of Bangladesh.

Diversity, relatedness, and ecological interactions of toxigenic Vibrio cholerae O1 populations in two distinctive habitats, the human intestine and the aquatic environment, were analyzed. Twenty environmental isolates and 42 clinical isolates were selected for study by matching serotype, geographic location of isolation in Bangladesh, and season of isolation. Genetic profiling was done by enterobacterial repetitive intergenic consensus sequence–PCR, optimized for profiling by using the fully sequenced V. cholerae El Tor N16961 genome. Five significant clonal clusters of haplotypes were found from 57 electrophoretic types. Isolates from different areas or habitats intermingled in two of the five significant clusters. Frequencies of haplotypes differed significantly only between the environmental populations (exact test; P < 0.05). Analysis of molecular variance yielded a population genetic structure reflecting the differentiating effects of geographic area, habitat, and sampling time. Although a parameter confounding the latter differences explained 9% of the total molecular variance in the entire population (P < 0.01), the net effect of habitat and time could not be separated because of the small number of environmental isolates included in the study. Five subpopulations from a single area were determined, and from these we were able to estimate a relative differentiating effect of habitat, which was small compared with the effect of temporal change. In conclusion, the resulting population structure supports the hypothesis that spatial and temporal fluctuations in the composition of toxigenic V. cholerae populations in the aquatic environment can cause shifts in the dynamics of the disease.

Structural and functional analysis of whole-soil microbial communities for risk and efficacy testing following microbial inoculation of wheat roots in diverse soils

The increasing use of genetically engineered or modified microorganisms (GEMs) has led to regulations regarding the safety of their use. Intended (target) effects and unintended (non-target) effects of GEMs must currently be evaluated prior to field testing or commercial use. We present soil and rhizosphere microbial community effects testing of two GEMs, Pseudomonas chlororaphis 3732RN-L11 and Pseudomonas fluorescens 2-79RN-L3, parental strains of these organisms and an uninoculated treatment using five diverse soils planted to wheat. An assay using BIOLOG w GN plates measured microbial community functional responses on wheat roots with adhering soil. Overall differences using multivariate statistical methods were highest at inoculation, and these effects persisted while the inoculated organisms were detectible on selective media. Differentiation based on lacZY genes engineered to the chromosome of both GEMs was significant for the 3732 GEM in all five soils tested, but not for the 2-79 GEM in a single soil. Lactose utilization in uninoculated microbial communities varied around a low baseline value. Direct fatty acid extraction and analysis of soil from around wheat roots was also performed using a novel method. Fatty acid analysis differentiated the 3732 GEM from all other treatments, but did not distinguish the 3732 parent inoculated from uninoculated treatments. As with the BIOLOG assay, multivariate statistical differences from fatty acid analysis decreased between GEM inoculated and uninoculated populations as viable counts of the GEM declined. Neither assay showed measurable community-level effects when inoculated organisms declined below detection, though three of six soils with surviving GEM populations still had significant effects after 105 days. Published by Elsevier Science Ltd.

Simple Sari Cloth Filtration of Water Is Sustainable and Continues To Protect Villagers from Cholera in Matlab, Bangladesh

ABSTRACT A simple method for filtering water to reduce the incidence of cholera was tested in a field trial in Matlab, Bangladesh, and proved effective. A follow-up study was conducted 5 years later to determine whether the filtration method continued to be employed by villagers and its impact on the incidence of cholera. A total of 7,233 village women collecting water daily for their households in Bangladesh were selected from the same study population of the original field trial for interviewing. Analysis of the data showed that 31% of the women used a filter of which 60% used sari filters for household water. Results showed that sari filtration not only was accepted and sustained by the villagers and benefited them, including their neighbors not filtering water, in reducing the incidence of cholera, the latter being an unexpected benefit. IMPORTANCE A simple method for filtering pond and river water to reduce the incidence of cholera, field tested in Matlab, Bangladesh, proved effective in reducing the incidence of cholera by 48%. A follow-up study conducted 5 years later showed that 31% of the village women continued to filter water for their households, with both an expected and an unexpected benefit that filtration had both a direct and indirect effect in reducing cholera (chi-square statistic of 1,591.94; P = <0.0001). Results of the study showed that the practice of filtration not only was accepted and sustained by the villagers but also benefited those who filtered their water as well as neighbors not filtering water for household use in reducing the incidence of cholera. A simple method for filtering pond and river water to reduce the incidence of cholera, field tested in Matlab, Bangladesh, proved effective in reducing the incidence of cholera by 48%. A follow-up study conducted 5 years later showed that 31% of the village women continued to filter water for their households, with both an expected and an unexpected benefit that filtration had both a direct and indirect effect in reducing cholera (chi-square statistic of 1,591.94; P = <0.0001). Results of the study showed that the practice of filtration not only was accepted and sustained by the villagers but also benefited those who filtered their water as well as neighbors not filtering water for household use in reducing the incidence of cholera.