9260 A. Introduction
1. General Discussion
cludes 11 microbes for methods development and potential future regulation.8,9
Water contamination and disease transmission may result
from conditions generated at overloaded and/or malfunctioning
sanitary waste disposal and potable water treatment systems. In
addition, common outdoor recreationalactivities, such as swimming (including pools and hot tubs), wind surﬁng, and waterskiing, all place humans at risk of waterborne diseases from
ingestion or direct contact with contaminated water.10 Outbreaks
of gastroenteritis, pharyngoconjunctivitis, folliculitis, otitis, and
pneumonia are associated with these recreational activities.
Overcrowded parks and recreational areas contribute to thecontamination of surface and groundwater.
Laboratory diagnosis of infectious disease depends on detection or isolation of the etiologic agent or demonstration of
antibody response in the patient. Environmental microbiological
examinations are conducted for compliance monitoring of the
environment, to troubleshoot problems in treatment plants and
distribution systems, and in support ofepidemiological investigations of disease outbreaks. Ideally, the public health microbiologist can contribute expertise in both clinical and environmental microbiology, thereby facilitating epidemiological investigations.
When testing for pathogens in environmental samples, it is
advisable to include analyses for indicator organisms. Currently,
coliforms (total coliform, thermotolerant coliform, and E.coli)
are used as water quality indicators. Fecal streptococci, enterococci, Clostridium perfringens, Bacteroides, Biﬁdobacterium,
and bacteriophages have been proposed as water quality indicators. No single indicator provides assurance that water is pathogen-free. The choice of monitoring indicator(s) presupposes an
understanding of the parameters to be measured and the relationship of theindicator(s) to the pathogen(s). Some bacterial
pathogens, such as Pseudomonas, Aeromonas, Plesiomonas,
Yersinia, Vibrio, Legionella, and Mycobacterium, may not correlate with coliform indicators. Traditional bacterial indicators
also may not correlate with viruses or parasites in pristine waters
or groundwaters, and they may be of limited utility in estuarine
and marine waters. Nevertheless,tests for total and fecal bacteria
and E. coli are useful, because it is rare to isolate bacterial enteric
pathogens in the absence of fecal contamination.
Other more general indicators may be of value also for assessing the potential for pathogen contamination and interpreting
culture results. Heterotrophic plate count provides information
about the total numbers of aerobic organotrophicbacteria and an
indication of the total organic composition of the aquatic environment. Physicochemical factors, such as turbidity, pH, salinity,
temperature, assimilable organic carbon, dissolved oxygen, biochemical oxygen demand, and ammonia, may provide useful
information about contamination or the potential of water to
support bacterial growth. For treated waters, chlorine residual
should bemeasured at the sample collection point.
One purpose of drinking water and wastewater treatment is to
reduce the numbers of viable organisms to acceptable levels, and
to remove or inactivate all pathogens capable of causing human
disease. Despite the remarkable success of water treatment and
sanitation programs in improving public health, sporadic cases
and point-source outbreaks ofwaterborne diseases continue to
occur. Water and wastewater may contain a wide variety of
bacteria that cause intestinal or extra-intestinal infections. Waterborne pathogens enter human hosts through intact or compromised skin, inhalation, ingestion, aspiration, and direct contact
with the mucous membranes of the eye, ear, nose, mouth, and
genitals. This section provides an introduction to bacterial...