3rd MICROBIOLOGY SEMINAR. Sanitary Microbiology. Current issues facing the developed and developing world. Dr Gavin Collins Microbial Ecology Lab (3783) Environmental Change Institute (5047). Sanitary Microbiology. WATER…. … is responsible for, by some estimates, approximately. 80%.
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… is responsible for,
by some estimates, approximately
of all infectious disease -
not just waterborne diseases,
but any disease
where water plays a role… WATER
Water-washeddiseases, such as trachoma, scabies, dysentery, louse-borne fever;
Water-based diseases, such as schistosomiasis, and Guinea worm;
And water-related diseases (involving an insect vector) such as malaria, sleeping sickness, or onchocerciasis.
H2O can act as a vector for the transmission of bacterial, viral and protozoan agents which cause a variety of diseases (mainly intestinal)
It can also be linked to worm invasions and viral/protozoan diseases transmitted by insects (aquatic hosts or insect breeding in H2O - indirect)
Water-associated diseases can be classified under 4 different categories: -
Mainly enteric diseases resulting from the ingestion of faecally-contaminated H2O (man, animal and bird excreta)
In developed countries, classical H2O -borne diseases are mostly low infective dose infections - cholera and typhoid fever (rare), leptospirosis (rare); viral infections; Campylobacter (bacterium) and Giardia and Cryptosporidium (protozoa) infections - becoming more common in Ireland
All water borne diseases can also be transmitted by other routes that permit ingestion of faecal matter - e.g. contaminated food
Diseases caused by pathogens carried by
insects that live near H2O and act as
Very difficult to control and diseases are very
with increased flooding leads to
breakdown of sanitary infrastructure and further spread of disease
(such as water treatment and distribution systems)
(increasing numbers of elderly & immuno-suppressed people)
Bovine generated CH4
CO2 from industry
Biogas (CH4 & CO2)
The diseases that result from flooding vary according to geographic region.
Typical ones include cholera, typhoid, dengue, Rift Valley fever, malaria, hepatitis A, AGI [acute gastro-intestinal illness], and ARI [acute respiratory illness].
The remaining time, 22 hours per day, water sits stagnant in the distribution system. In addition to pathogens in drinking water, slums tend to be sited near standing water.
Moreover, children routinely play in this water - both fouling it and further exposing themselves to disease.
Standing water is a major problem in malaria and other vector-borne diseases.
Cholera, giardiasis, hepatitis, shigellosis, typhoid, and AGI
Other infections such as legionellosis, cryptosporidiosis, and mycobacterial infections occur, but are seldom diagnosed.
Often in the developing world gastroenteritis and other infections cause unnecessary mortality
1) No treatment
2) Breakthrough at treatment plant
3) No disinfectant residual
4) Direct sewage contamination through pipe
leakage, breakage, back-siphoning, and
Corrosion of pipe networks allowing contamination during distribution
30% of rivers polluted;
50% of group water supplies contaminated with E. coli
formation leads to:
Current indicator organisms may not be adequate for the following reasons:
The presence of coliforms in water only
reflects sewage contamination - not potential
pathogens like Legionella
Coliform behaviour and die-off is not
comparable to the behaviour of viruses and
Die-off rates of faecal coliforms have been
demonstrated to vary enormously
Techniques used to identify indicators rely on growth and culture - many organisms can be viable in the environment but unculturable using current methods(‘Plate-count anomaly’)
Molecular methods based on DNA probes and PCR still not adequate
Legionella pneumophila an emerging
pathogen - first recognized in the 1970s
Example of how creation of a unique
environment in our water systems that has
lead to a "new" or newly recognized disease.
Incidence of Legionnaires' disease in the U.S.:
approximately 1,000 cases annually
Estimated that over 25,000 cases of the illness
occur each year, causing more than 4,000 deaths.
community-acquired pneumonia. Difficult to
distinguish, many cases go unreported.
For growth Legionella requires the following:
stagnation; temps between 20° and 50°C (optimal
growth range is 35° - 46°C);
pH between 5.0 and 8.5;
Microbes incl algae, flavobacteria, and Pseudomonas,
which supply essential nutrients or harbor the
growth in many modern buildings:
Domestic hot-water systems with water
heaters that operate below 60°C; centralized
hot water systems [common in eastern
Cooling towers, and fluid coolers that use
evaporation; humidifiers and decorative
fountains that create a water spray; spas
Protozoa and common causes of GI infections
Used to be rare in Ireland, incidence now
Form oocysts as part of the life-cycle
These oocysts are resistant to chlorination
which is the only method used to disinfect
water in Ireland
organisms at the moment
Use of conventional indicators
How many of the 350,000 cases of food/water borne illnesses in Ireland last year caused by these organisms??
1. Active surveillance
2. Population surveys
3. Low-cost solutions to treatment
4. Waste-water reclamation
6. Assessments of impacts of engineered "ecosystems”
7. Monitoring of antibiotic resistance and changing virulence