Indicator Microorganisms

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Indicator Microorganisms

• Criteria for ideal indicator m.o.

should be a member of the intestinal microflora
of warm-blooded animals should be present when
pathogens are present should be present in
greater number than the pathogen should be
equally resistant as the pathogen to
environmental insults should not multiply in the
environment
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should be detectable by means of easy, rapid,
and inexpensive methods should be non-pathogenic
Commonly used indicator m.o. (APHA, 1989)
Total Coliforms aerobic facultative
anaerobic, G-ve, nonspore-forming,
rod-shaped, ferment lactose with gas
production within 48 hours at 35 oC
e.g. E. coli, Enterobacter, Klebsiella,
Citrobacter
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Commonly used indicator m.o. (cont.)
discharged in high No.(2x109
coliforms/day/capita) in human and animal
fecae determine quality of potable water,
shellfish harvesting waters recreational
waters less sensitive than viruses or
protozoan cysts to environmental factors
and disinfection
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• Fecal Coliforms
• all coliforms that can ferment lactose at
• 44.5oC e.g. E. coli, Klebsiella pneumoniae
• have survival pattern the same as bacterial
• pathogen indicate the contamination from fecae
  of warm-blooded animals
• less resistant to disinfection than virus
• and cysts
• Detection
• MPN, membrane filtration, EC broth, m-FC agar
  (44.5oC), M-T7 agar (37oC), rapid method
  (ONPG-MUG PCR)

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Fecal Streptococci S. faecalis, S. bovis, S.
equinus and S. avium colonized in intestinal
of human and warm-blooded animals subgroup of
them enterococci (S. faecalis S. faecium)
used as indicator for presence of virus ratio
FC/FS used as indicator for origin of surface
water pollution (FC/FS gt 4, FC/FS lt 0.7)
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Anaerobic bacteria Clostridium perfringens
(Gve, rod, spore-forming) Bifidobacteria
(Gve, nonspore-forming) Bacteroides
spp. Fluorescent antiserum
Bacteriophages fast and easy to detect
more than enteric virus used as indicator for
assess efficiency of water wastewater
treatment plant Detection phage
concentration decontamination of concentrate
phage assay
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Yeasts Acid-fast organisms indicator for
disinfection efficiency

• Heterotrophic Plate Count (HPC)
• aerobic and facultative anaerobic bacteria
  that use carbon and energy from org. cpd.
• No. of recovery bact. depend on medium
• composition, period of incubation, temp.
• Pseudomonas, Aeromonas, Aeromonas,
  Klebsiella, Proteus, Flavobacterium,
  Enterobacter, Citrobacter, Serratia,
  Acinetobacter, Alcaligenes, Moraxella

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• in drinking water vary from lt 1 CFU/ml to gt
• 104 CFU/ml
• most sensitive indicator for removal and
• inactivation of microbial pathogen in reclaimed
  
• wastewater
• Detection
• plate count agar 35oC, 48 hrs
• R2A medium 28oC, 5-7 days
• should not more than 500 colony/ml

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Chemical indicator of water quality Fecal
sterols coprostanol, coprosterol,
cholesterol, coprostanone Free chlorine
residual Level of endotoxin lipopolysacc.
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Toxicity testing using m.o.

• release of gt 50,000 xenobiotics into the
• environment
• impact determined by acute and
• chronic toxicity tests (fish and
  invertebrate
• bioassays)
• short-term bioassays micro-biotests
• based on inhibition of the activity of
• enzymes, bacteria, fungi, algae and protozoa

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Toxicants
Advantages simple, rapid, cost-effective
and can be miniaturized
1. Heavy metal - e.g. Cd, Cr, Pb, Hg,
Ag - toxicity is mainly due to soluble
metals which controlled by various factors
such as pH, type and conc. of
complexing agents, redox potential etc.
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2. Organic toxicants - e.g. phenolic
compounds - inhibitors affect substrate
removal by m.o. in the manner similar way
they affect enzyme activity