Download Drinking Water Micro 101 - Ohio Water Professionals

OTCO Water Laboratory Analyst
Workshop May 17, 2012
Microbiological Laboratory Update
Drinking Water Micro 101.1
Todd W. Bidlack
Laboratory Evaluation Officer
Ohio EPA/DES/Lab Certification Section
The human body contains hundreds of species
of microorganisms in a living, evolving,
ecosystem that make up our normal flora.
The normal flora of the enteric or digestive
system contain many beneficial
microorganisms.
• Help digest food
• Help regulate our metabolic process
• Help fend off ‘unfriendly’ microorganisms
that have been ingested
Microbial pathogens that can cause
disease when ingested will pass
through the digestive system and exit
with feces.
• Specific potential pathogens are too
numerous to isolate individually, occur at
relatively low concentrations, and are much
more difficult to test for in water.
Total coliform & E. coli are bacterial
indicators of microbial contamination in
drinking water.
• Total coliform & E. coli occur normally and in
great numbers in the enteric system of humans and
other warm-blooded animals.
• The microorganisms are relatively easy and
inexpensive to test for.
• When these indicators occur at specific levels, the
risk is great enough the water should not be
consumed.
In the realm of microbiology &
microorganisms there are always
many exceptions.
• The normal flora of our digestive system
contains E. coli & we could not survive
without it.
• But good bacteria by genus & species can
develop into bad or pathogenic strains that
may cause disease in some individuals.
There are also opportunistic pathogens.
• These microbes may have no effect on most
healthy individuals.
• But, infants, elderly, and/or individuals
with a compromised immune system due to
medical condition, and/or treatment may
become ill.
When we look at drinking water we are
dealing with living dynamic
microorganisms that may have been away
from the host for a period of time and may
be attenuated and not produce a typical
laboratory reaction.
• This can lead to alternative metabolic pathways
evolving in some microorganisms to survive and
maintain their existence in the environment.
• This is why environmental microorganisms are
much more difficult to test for.
• Clinical specimens are taken directly from the
human host, typically occur in large numbers, &
have a strong analytical test response.
• ATCC pure cultures grown in ideal laboratory
conditions and delivered into an ideal sterile matrix of
laboratory pure water have well defined analytical test
reactions.
So what are total coliform bacteria?
• Group of several genera belonging to the
family Enterobacteriaceae.
• Traditionally include members from:
Escherichia, Citrobacter, Klebsiella, &
Enterobacter.
• But, may also include some Serratia,
Hafnia, etc.
Since the total coliform group is rather broad
based from a taxonomical approach it has
often been based or defined by more
specific analytical reactions.
• Historical definition based on fermentation
technique has been: all gram-negative, facultative
anaerobic, non-spore forming, rod shaped bacteria,
that ferment lactose with acid & gas production
within 48 hours at 35 degrees C.
• With the advent of MMO-MUG the total coliform
group is now defined as all bacteria possessing the
enzyme β-D-galactosidase which cleaves the
chromogenic substrate resulting in chromogen
release.
So… What does MMO-MUG stand for?
Minimal Medium ONPG-MUG test
• ONPG – ortho-nitrophenyl-βgalactopyranoside test reagent used to
determine β-galactosidase activity of
the family Enterobacteriaceae
• MUG – 4-methylumbelliferyl-β-Dglucuronide
Drinking Water Laboratory Certification
Website
http://www.epa.ohio.gov/ddagw/labs.aspx