Question

Environmental Microbiology.

Describe the difference between microbial source tracking and identification of indicator organisms?

Answer 1

These methods are required to track the origin of fecal pollution.

These are mainly used to assess the safety of drinking water, harvesting seafood and water used for recreation.

Their contamination may risk human health and closure of harvesting areas and beaches.

Contaminated water contains pathogens like Salmonella enterica, Shigella sp., Hepatitis A virus, etc.

Indicator microorganisms

These have been used traditionally to predict fecal water pollution.

Indicators are non-pathogenic, detected rapidly, are easily enumerated and can be strongly associated with the presence of pathogenic microorganisms.

Following microorganisms can be used,

• E.coli: nonpathogenic, may not be reliable in tropical and subtropical environments as it can replicate in contaminated soil.
• Enterococcus spp: used for marine and recreational waters.
• C. perfringens: useful where the prediction of the presence of viruses and remote fecal pollution is desirable.

They are useful in a way that they circumvent the need to assay every pathogen present in water.

Many of these microorganisms are present not only in humans but also in the intestines of warm-blooded animals. Because of this ubiquitous nature of these organisms, their effectiveness is limited.

The shortcomings of the above-mentioned microorganisms for the assessment of fecal pollution are becoming increasingly apparent.

The advent of microbial source tracking technologies has enhanced the abilities of these traditional microorganisms for predicting fecal pollution.

Microbial source tracking

Following methods can be used,

• microbiological
• genotypic method
• phenotypic method
• chemical method

These methods characterize indicator microorganisms for detecting subtle differences present within different groups of microorganisms that can subsequently be used to identify the environment from where the organisms were derived.

The genetic methodology can differentiate different lineages of bacteria found within different animal hosts. Over a period of time, a group of organisms in a host will possess a similar genetic fingerprint which differs from the organisms that adapted to a different host or environment.

The phenotypic method within different lineages of bacteria focuses on traits acquired from exposure to different hosts or environments.

Direct monitoring of pathogens in water assessed for fecal pollution can also be done but they are not readily detectable.

The use of chemical methods is based on the fact that human and animal communities utilize different substances and produce different by-products that can be traced back to the source of pollution.