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Applied and Environmental Microbiology, July 2001, p. 3328-3330, Vol. 67, No. 7
International Centre for Diarrhoeal Disease
Research, Bangladesh, Dhaka 1000, Bangladesh1;
Center of Marine Biotechnology,
University of Maryland Biotechnology Institute, Baltimore, Maryland
212022; and Department of Cell
Biology and Molecular Genetics, University of Maryland, College Park,
Maryland 207423
Received 8 February 2001/Accepted 20 April 2001
Five tube-wells in Matlab, Bangladesh, were selected for analysis
of selected biophysicochemical parameters. The results showed that all
tube-well water samples contained zooplankton and bacteria. Results for
some of the parameters were outside the accepted limits recommended by the World Health Organization for drinking water. It is
concluded that water from tube-wells should be treated if used as
drinking water.
Tube-well water is used primarily as
a source of drinking water by the vast majority (90%) of the rural
population in Bangladesh (16). A tube-well is a
small-diameter cased well fitted with a cast iron suction hand pump
(1). These tube-wells have been installed in Bangladesh at
various depths, depending on availability and the level of groundwater.
In many cases, immediate environmental conditions are unfavorable;
e.g., the distance of tube-wells from latrines or sewage-contaminated
ponds or tanks may be insufficient to avoid contamination of the well
water with human-pathogenic bacteria. Tube-wells have failed to protect
against gastrointestinal diseases in Bangladesh, despite regular use of
tube-well water for drinking (14). Recent studies have
demonstrated that underground water systems are increasingly vulnerable
to both microbiological and heavy metal contamination, especially by
arsenic, in Bangladesh. Such problems arise even in developed
countries. For example, in 1994, an outbreak of cryptosporidiosis
occurred in a rural community in Washington State, where water was
supplied by two deep, unchlorinated wells (4).
Besides chemical contaminants, eukaryotic microorganisms (protists) are
also a significant component of microbial communities inhabiting
groundwater aquifers. This is not unexpected, considering that many
protists feed heterotrophically, via either phagotrophy (bacterivory)
or osmotrophy (able to grow in the dark on dissolved organic carbon).
Protistan numbers in water are usually low (<102
per g [dry weight]) in pristine, uncontaminated aquifers but may
increase by several orders of magnitude in polluted aquifers with a
high organic content. Small flagellates (typically 2 to 3 µm in size
in situ) are by far the dominant zooplankton in aquifers, although
amoebae and occasionally ciliates may also be present in relatively
lower numbers (17). In Bangladesh, tube-wells have been
installed in every village to provide a drinking water source other
than rivers and streams, since centralized water treatment systems are
not available, at least for the foreseeable future. Therefore,
villagers use tube-well water as an assumed safe drinking water source.
Since there is a paucity of information concerning protists and other
microorganisms in tube-well water, this study was undertaken to address
that information gap.
In Matlab, Bangladesh, five tube-wells of various depths (60 to 180 ft)
and presently in use in geographically separated villages and assumed
safe drinking water sources were selected for study. Plankton analysis
was done by filtering 50 liters of tube-well water through a plankton
net (20-µm mesh size). The concentrated samples (50 ml) were
collected in 4-oz sterile glass bottles. In addition, 500-ml water
samples were aseptically collected directly from the tube-wells, using
sterile Nalgene plastic bottles. All samples were transported directly
to the laboratory at the International Centre for Diarrhoeal Disease
Research, Bangladesh, Dhaka, Bangladesh, in a transport box filled with
cool packs (Johnny Plastic Ice, Pelton Sheperd, Stockton, Calif.). The
plankton samples were counted within 48 h, using a
Sedgewick-Rafter counting chamber, a nanoplankton counting chamber, and
a light microscope, according to procedures described by Elliot
(5) and Greenberg et al. (6).
Samples of water (100 ml) were filtered through a 0.22-µm-pore-size
membrane filter (Millipore Corp.), and the filters were placed on
membrane fecal coliform (MFC) agar plates. Plates were incubated
at 37 and 44°C for 18 to 24 h to estimate numbers of total and
fecal coliforms, respectively.
From each tube-well water sample, 100 µl was inoculated onto nutrient
agar using the drop plate technique (8), and inoculated plates were incubated at 37°C for 18 to 24 h. Total viable
bacteria were enumerated and recorded as CFU per milliliter.
Acridine orange total count.
Total direct counts of bacteria
in the water samples were obtained by the method of Hobbie et al.
(7) using Nucleopore filter membranes and fluorescence microscopy.
Direct viable count.
One milliliter from each of the tube-well
water samples was enriched with 50 µl of 2% yeast extract and 10 µl of nalidixic acid (1 mg/ml) and incubated at room temperature
overnight in the dark, after which the samples were fixed with formalin
(2%). Five-microliter portions of the fixed samples were placed on a polytetrafluoroethylene-coated slide and air dried. After fixation with
methanol, the samples were stained with 0.01% acridine orange in the
dark for 3 min (13). Both nonelongated and elongated cells
were counted as total bacteria and only elongated cells were counted as
viable bacteria, using a fluorescence microscope and according to the
procedures described by Islam et al. (11).
Physicochemical parameters.
Conductivity, salinity, and total
dissolved solids (TDS) were measured using a portable meter (HACH C0150
conductivity meter, model 50161). The pH of the water samples was
measured using a digital pH/multivolt meter (Orion Research model 611).
Hardness was estimated by the titrimetric method of Greenberg et al.
(6). The arsenic content of the tube-well water was also
measured, using a commercial kit (MerckoQuant; E. Merck, Darmstadt,
Germany), following the manufacturer's instructions.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.7.3328-3330.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Microbiological Analysis of Tube-Well Water in a
Rural Area of Bangladesh
ABSTRACT
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TABLE 1.
Biophysicochemical parameters of water samples collected
from five tube-wells in Matlab, Bangladesh
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ACKNOWLEDGMENTS |
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This research was supported by NIH grant 1RO1A139129-01 and U.S. Environmental Protection Agency grant R824995-01 to the University of Maryland Biotechnology Institute (UMBI), Baltimore, and by the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B). ICDDR,B is supported by agencies and countries which share its concern for the health problems of developing countries. Current donors include the aid agencies of the governments of Australia, Bangladesh, Belgium, Canada, China, Denmark, Germany, Japan, The Netherlands, Norway, Republic of Korea, Saudi Arabia, Sri Lanka, Sweden, Switzerland, Thailand, the United Kingdom and the United States; international organizations, including the Arab Gulf Fund, Asian Development Bank, European Union, the United Nations Children's Fund (UNICEF), the United Nations Development Program (UNDP), the United Nations Population Fund (UNFPA), and the World Health Organization (WHO); private foundations, including the Aga Khan Foundation, Child Health Foundation, Ford Foundation, Population Council, Rockefeller Foundation, and Sasakawa Foundation; and private organizations, including American Express Bank, Bayer AG, CARE, Family Health International, Helen Keller International, The Johns Hopkins University, Macro International, New England Medical Center, Procter and Gamble, RAND Corporation, SANDOZ, Swiss Red Cross, the University of Alabama at Birmingham, the University of Iowa, and others.
We thank M. Anisur Rahman for assistance in preparation of the manuscript.
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FOOTNOTES |
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* Corresponding author. Mailing address: Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Suite 236, Columbus Center, 701 East Pratt St., Baltimore, MD 21202. Phone: (702) 292-8000. Fax: (702) 292-8000. E-mail: colwell{at}umbi.umd.edu.
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REFERENCES |
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Applied and Environmental Microbiology, July 2001, p. 3328-3330, Vol. 67, No. 7
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.7.3328-3330.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
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(2003). Reduction of cholera in Bangladeshi villages by simple filtration. Proc. Natl. Acad. Sci. USA
100: 1051-1055
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