Water Analysis and Coliform Bacteria

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Questions and Answers

What is a major challenge in water analysis for detecting pathogens?

Pathogens transform into harmless bacteria.

Pathogen numbers may be too low to detect. (correct)

Pathogen levels may be too high to detect.

Only one pathogen type can contaminate water.

Which type of bacteria is primarily tested as an indicator of fecal contamination?

E.coli

Coliform Bacteria (correct)

Salmonella

Staphylococcus aureus

What type of testing method focuses on identifying fecal indicator bacteria?

Physical Water Analysis

Chemical Water Analysis

Bacteriological Water Analysis

Microbiological Water Analysis (correct)

What is the primary reason it is impractical to test for all pathogens in collected water samples?

There are too many possible pathogens. Signup and view all the answers

How long can the isolation and detection of some pathogens take?

Several days to weeks Signup and view all the answers

Which sample is utilized in microbiological water analysis?

Water Samples Signup and view all the answers

What environmental condition can affect water testing results?

The temperature of the water Signup and view all the answers

Why is it difficult to conduct thorough water testing for pathogens?

Some pathogens require complex testing methods. Signup and view all the answers

Which method is NOT typically included in water testing?

Genetic Testing Signup and view all the answers

What type of bacteria does mFC agar primarily inhibit?

Non-lactose fermenting bacteria Signup and view all the answers

What color do fecal coliforms form on mFC agar?

Blue Signup and view all the answers

At what temperature should the membrane be incubated to detect fecal coliforms?

44.5 C Signup and view all the answers

What is the pore size of the membrane used in the membrane filtration technique?

0.45 mm Signup and view all the answers

What role does aniline blue serve in the mFC agar?

Indicates pH changes Signup and view all the answers

What is the primary purpose of using membrane filtration in the detection of indicator microorganisms?

To concentrate bacteria Signup and view all the answers

What is the purpose of testing water for the presence of pathogenic bacteria?

To identify fecal contamination Signup and view all the answers

What is the limitation of testing for pathogenic bacteria directly?

Pathogens occur in small numbers and might be missed Signup and view all the answers

Which of the following is considered an indicator organism for water contamination?

Escherichia coli Signup and view all the answers

What characterizes coliform bacteria?

They ferment lactose and can produce gas Signup and view all the answers

How does the density of microorganisms relate to water pollution?

Higher density indicates a more polluted water sample Signup and view all the answers

Which of the following bacteria is commonly found in improperly maintained sewage systems?

Clostridium perfringens Signup and view all the answers

What indicates that soil bacteria have contaminated the water supply?

Heavy rains washed them into the water Signup and view all the answers

What is the significance of a minimum burden of 10 coliforms per 100 ml?

It suggests possible contamination with pathogens Signup and view all the answers

What role do natural water bacteria serve in assessing water quality?

They signal the absence of pollution Signup and view all the answers

Which of the following bacteria is not a natural inhabitant of water?

Proteus sp. Signup and view all the answers

What temperature range do thermotolerant coliforms typically grow at?

44–45ºC Signup and view all the answers

Which coliform is considered the best indicator of fecal pollution?

Escherichia coli Signup and view all the answers

What is the primary characteristic that allows E. coli to ferment lactose?

Production of indole from tryptophan Signup and view all the answers

Which method involves using sterile growth medium to analyze water samples?

Multiple tube fermentation method Signup and view all the answers

Which type of coliforms are specifically present in the gut and feces of warm-blooded animals?

Fecal coliforms Signup and view all the answers

Which characteristic is NOT associated with E. coli?

Does not possess β-galactosidase Signup and view all the answers

What role do total coliforms play in water analysis?

They indicate the bacterial contamination level. Signup and view all the answers

Which bacteria are included in the group of thermotolerant coliforms?

Escherichia coli and Klebsiella sp. Signup and view all the answers

What is a common environment where total coliforms can be found?

Soil and water influenced by surface water Signup and view all the answers

Which of the following tests is most basic for assessing bacterial contamination in water?

Total coliforms test Signup and view all the answers

What is the purpose of the multiple tube test in drinking water analysis?

To assess total and fecal coliforms Signup and view all the answers

Which reaction indicates a positive result in the presumptive test?

Fermentation of lactose to acid and gas Signup and view all the answers

What is the main characteristic of coliform colonies on EMB agar?

Coliforms typically have a metallic sheen Signup and view all the answers

What do atypical total coliform colonies on EMB agar lack?

Metallic sheen from extensive aldehyde production Signup and view all the answers

What medium is used in the culture stage after the presumptive test?

EMB (Eosin-Methylene Blue) agar Signup and view all the answers

In the completed test, what confirms a positive result?

Production of acid and gas Signup and view all the answers

What appearance do E. coli colonies typically exhibit on EMB agar?

Metallic sheen Signup and view all the answers

What agent causes the color change in the EMB agar?

Acid production from lactose fermentation Signup and view all the answers

How is the dilution process carried out in the presumptive test?

The sample is diluted and added to lactose fermentation tubes Signup and view all the answers

What role do gas and acid play in interpreting the results of the coliform testing?

They show successful fermentation and presence of coliforms Signup and view all the answers

Study Notes

Water Analysis

Water analysis is crucial for identifying pathogenic bacteria in water sources.
Common challenges include the low numbers of individual pathogens and the time required to isolate and detect them.
Water pollution by fecal contamination is a significant concern due to the presence of pathogens in small concentrations and the large number of possible pathogens.
It is not practical to test for every pathogen, so indicator organisms, like coliform bacteria, are used to indicate fecal contamination.
Indicator organisms are microorganisms that are not naturally found in water and are present only when fecal contamination occurs.
Their density is proportional to the degree of contamination, with higher density indicating more pollution.
Indicator organisms provide indirect evidence of pathogen presence, with a focus on coliform bacteria as a common indicator.
The minimum burden for coliform bacteria is 10 coliforms per 100 ml of water.

Coliform Bacteria

Coliform bacteria are aerobic or facultative anaerobic, gram-negative bacilli.
They are non-spore forming and ferment lactose with acid production.
Some coliform bacteria can produce gas (hydrogen sulfide).
Thermotolerant coliforms can grow at 44 or 44.5ºC.
Examples of thermotolerant coliforms include Escherichia coli, Citrobacter freundii, Enterobacter, Klebsiella pneumoniae, and Serratia.
Total coliforms include bacteria found in soil, surface water, and human or animal waste.

Water Analysis Methods

The Multiple Tube Fermentation Method is used to assess total and fecal coliforms in drinking water.
- It involves a series of dilutions and incubations with lactose fermentation tubes.
- Positive reactions are indicated by fermentation of lactose, producing acid and gas.
- The method consists of three stages:
  - Presumptive Test: Dilution from a water sample is added to lactose fermentation tubes.
  - Culture: Samples from positive presumptive tubes are streaked onto EMB (Eosin-Methylene Blue) agar.
  - Completed Test: Isolated lactose-positive colonies from EMB are inoculated into lactose broth and nutrient agar slant.
The Membrane Filtration Method involves filtering a measured volume of water through a membrane with a pore size of 0.45 mm.
- Bacteria trapped on the membrane grow into colonies, allowing for bacterial density calculation.
- Filters for fecal coliform detection are incubated at 44.5°C for 22-26 hours.
- mEndo agar LES is a selective and differential growth medium used to detect total coliforms.
  - It contains lactose and a pH indicator that changes color when acid is produced.
  - Coliforms produce a metallic (golden) sheen due to aldehyde and acid production from lactose fermentation.
  - Some total coliforms may have dark red, mucoid colonies or a dark center without a metallic sheen.
- mFC agar is used to detect fecal coliforms.
  - It contains bile salts that inhibit bacteria other than fecal coliforms.
  - Rosolic acid, a pH indicator, turns dark blue when acid is produced, identifying lactose-fermenting bacteria.
  - Fecal coliforms form blue colonies, while E. coli forms flat dark blue colonies.

Escherichia Coli (E. coli)

E. coli is a member of the Enterobacteriaceae family, possessing β-galactosidase and β-glucuronidase enzymes.
It grows at 44-45°C on complex media, fermenting lactose and mannitol with acid and gas production.
It produces indole from tryptophan.
Some strains can grow at 37°C but not 44-45°C, and some do not produce gas.
E. coli does not produce oxidase or hydrolyze urea.
E. coli is considered the best indicator of fecal pollution and potential pathogen presence.

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Description

This quiz explores the importance of water analysis in identifying pathogenic bacteria, particularly focusing on coliform bacteria as indicator organisms for fecal contamination. It highlights the challenges of detecting individual pathogens and the role of coliforms in assessing water quality. Test your knowledge on these crucial concepts in environmental science.