Water Bacteriology Flashcards
Vehicle for many diseases that are caused by different microorganisms.
Water
Done to address problems of water potability.
Bacteriologic Examination of Water
Two Causes of Unsafe Drinking Water
- Direct contamination
2. Indirect Contamination
Human or animal feces.
Direct contamination
Improperly functioning sewage treatment systems
Indirect contamination
Top 10 Causes – Outbreaks in Public Water Systems (CDC)
- Giardia
- Legionella
- Norovirus
- Shigella
- Campylobacter
- Copper
- Salmonella
- Hepatitis A
- Cryptosporidium
- E.coli, excess fluoride (tie)
Contaminated water can transmit diseases
True
Diseases caused by contaminated water
- Diarrhea
- Cholera
- Dysentery
- Typhoid
- Polio
Total diarrheal deaths recorded each year according to WHO 2021
485, 000 diarrheal deaths
It is possible to test each water sample for each pathogen.
False. It is impossible to test each water sample for each pathogen
It is not easier to test for the presence of coliforms as indicator organisms.
False. It is much easier to test for the presence of coliforms as indicator organisms.
Which among the choices are true about Coliforms?
a. non-aerobic, non-facultatively, aerobic, gram-positive, endosporic, rod shaped bacteria
b. aerobic, non-facultative, gram-negative, endosporic, rod shaped bacteria
c. aerobic, facultatively aerobic, gram-negative, non-endospore forming, rod shaped bacteria
d. non-aerobic, facultatively aerobic, gram-positive, non-endospore forming, rod shaped bacteria
e. aerobic, facultatively aerobic, gram-positive, non-endospore forming, rod shaped bacteria
Letter C. Coliforms are aerobic or facultatively aerobic, gram-negative, non-endospore forming, rod shaped
Does coliforms ferment lactose?
Yes. Coliforms ferment lactose to form gas.
How many hours do coliforms incubate prior to forming gas?
a. 72 hours of incubation at 27 degree Celsius.
b. 48 hours of incubation at 31 degree Celsius.
c. 48 hours of incubation at 35 degree Celsius.
d. 40 hours of incubation at 35 degree Celsius.
e. 24 hours of incubation at 27 degree Celsius.
Letter C. Coliforms ferment lactose to form gas within 48 hours of incubation at 35 degree Celsius.
Which among the bacteria is the most predominant coliforms to cause disease in human?
a. Escherichia coli
b. Enterobacter
c. Klebsiella
d. Salmonella
Letter A. The most pre-dominant coliforms ever to cause disease in humans is Escherichia coli or E.coli.
When E.coli is present in water, what does it indicate?
a. It is contaminated with dirt.
b. It is contaminated with urine from animals.
c. It is contaminated with fecal matter.
d. It is contaminated with urine from humans.
e. It is contaminated from improper sewage systems.
Letter C. The presence of E.coli in water indicates that it is contaminated with fecal matter.
Aside from E. coli, there are other fecal coliforms that could contaminate drinking water:
a. Klebsiella and Enterobacter species.
b. Klebsiella and Campylobacter species
c. Enterobacter and Campylobacter species
d. Enterobacter and Shigella species
e. Legionella and Gardia species
Letter A. Klebsiella and Enterobacter species
Other forms of coliforms in drinking water are saprophytic. What does saprophytic mean?
a. intestinal in origin.
b. non-intestinal origin.
Letter B. Other forms of coliforms in drinking water are saprophytic, thus, non-intestinal in origin.
A dilution test which estimates the concentration of a target microbe in a water sample.
a. Bacteriologic Examination of Water (BEW)
b. Most Probable Number Test (MPN)
c. Multiple Tube Fermentation Technique (MTFT)
Letter B. Most Probable Number Test is a dilution test which estimates the concentration of a target microbe in a water sample.
TRUE or FALSE
MPN is not based on the application of probability to the number of observed negative growth responses to a single standard dilution.
False. MPN is based on the application of probability to the number of observed positive growth responses to a series of standard dilution.
Which among the choices is true ?
- Most Probable Number Test uses a single tube with selective broth.
- Multiple Tube Fermentation Technique uses a single tube with a non-selective broth.
- Most Probable Number Test uses a series of single tube with a non-selective broth.
- Most Probable Number Test uses a single tube with non-selective broth.
- Multiple Tube Fermentation Technique uses a series of tubes with selective broth.
- Multiple Tube Fermentation Technique uses a single tube with non-selective broth.
a. 2 of the choices.
b. only one of the choices.
c. 3 of the choices.
d. NOTA
d. AOTA
Letter B. Multiple Tube Fermentation Technique uses a series of tubes with selective broth.
The most probable number (MPN) of bacteria is obtained from the:
a. Number of tubes which show positive result.
b. A single tube which show positive result.
c. Number of tubes which show negative result.
d. A single tube which show negative result.
Letter A. Number of tubes which show positive result.
A statistical test that provides an estimate of the coliform contamination in the water sample or an estimate of the mean density of coliform in the sample.
Multiple Tube Fermentation Technique
State whether the assumption (MPN Test) is true or not:
Bacteria are not distributed randomly within a sample.
False. Bacteria are distributed randomly within the sample.
State whether the assumption (MPN Test) is true or not:
Bacteria are separated and are clustered together.
False. Bacteria are separated and not clustered together.
State whether the assumption (MPN Test) is true or not:
Every tube (or plate, wells) whose inoculum contains even one.
True.
State whether the assumption (MPN Test) is true or not:
Every tube (or plate, wells) whose inoculum contains one or more.
False. Every tube (or plate, wells) whose inoculum contains even one.
State whether the assumption (MPN Test) is true or not:
Viable organism will produce detectable growth or change in a certain period of time.
True
State whether the assumption (MPN Test) is true or not:
The result of the individual tubes of the sample is dependent.
False. The result of the individual tubes of the sample is independent.
It detects all lactose fermenters.
a. Confirmatory Test
b. Presumptive Test
Letter B. Presumptive Test
How often should you shake the water sample during presumptive test?
a. 30 times within 7 seconds
b. 25 times within 7 seconds
c. 20 times within 10 seconds
d. 20 times within 7 seconds
Letter B. 25 times within 7 seconds
(+) Double strength Lactose Broth (DLSB) = turbidity + minute bubbling
a. Presumptive Test
b. Confirmatory Test
a. Presumptive Test
Which among the choices is true?
- If no gas is observed, do not incubate the sample, and re-do the procedure.
- If no gas is observed, re-incubate for another 24 hours but there is no need to re-examine for gas.
- If no gas is observed, re-incubate for another 12 hours and re-examine for gas.
- If no gas is observed, re-incubate for another 24 hours and re-examine for gas.
- If no gas is observed, re-incubate for another 12 hours but there is no need to re-examine for gas.
a. only one
b. two of the choices
c. three of the choices.
d. NOTA
e. AOTA
Letter A. Statement 4 - if there is no gas observed, re-incubate for another 24 hours and re-examine for gas.
What should you do if there are still no gas after 48 hour incubation?
a. Report positive
b. Report negative
c. Stop the procedure and re do it.
d. NOTA
Letter B. If there are still no gas after 48 hour incubation, report it as negative.
If there are still no gas after 48 hour incubation, report it as negative. Do you still need a re-examination for this?
a. Yes
b. No
Letter B. If there are still no gas after 48 hour incubation, report it as negative. No other examination is needed.
TRUE or FALSE.
All primary fermentation tubes that shows gas at the end of 24-
48 hours, should be subjected to confirmatory test.
True
TRUE OR FALSE
Why is there a need to subject primary fermentation tubes that shows gas at the end of 24-
48 hours to confirmatory test?
To ensure that the coliforms are of fecal origins since there are other
organisms that ferments lactose as well.
True
What happens to the broth when gas is formed?
Cloudy
Do total coliforms estimate using MPN
Confirmatory Test
Confirmatory/Presumptive/Completed
Coliforms growing in the broth are confirmed (fecal origin or not) in Brilliant Green Lactose Bile Broth (BGLB)
Confirmatory Test
What does (+) in gas in BGLB indicates?
Presumptive evidence of gram-negative coliform microorganisms.
What does BGLB mean?
Brilliant Green Lactose Broth
TRUE or FALSE
Do not count the number of tubes with positive results and take note of the (Most Probable Number) MPN.
False. Count the number of tubes with positive results and take note of the (Most Probable Number) MPN.
Presumptive or Confirmatory
Count the number of tubes with positive results and take note of the (Most Probable Number) MPN.
Confirmatory Test
What is the normal value of MPN?
NOT greater than 2.2 MPN (+) BGLBB: Turbidity + minute bubbling
This phase is performed when it is necessary to know the species of bacteria in the water sample.
a. Confirmatory Test
b. Presumptive Test
c. Completed Test
Letter C
The presence of fecal coliform from human or animal feces is determined.
a. Completed Test
b. Presumptive Test
c. Confirmatory Test
Letter A.
Involves the isolation and identification of the coliform organism on culture media.
a. Presumptive Test
b. Completed Test
c. Confirmatory Test
Letter B.
Media used involved in the isolation and identification of the coliform organism.
E.coli broth or EC broth
In what degree and how many hours should you incubate EC broth?
Incubate it at 44-45 C for 18 hours.
What does this indicate: If (-) gas:
a. Inoculate to EMB with MIS Technique
b. Report completed test with MPN value.
c. Report confirmatory test with MPN value.
d. Report confirmatory test with MTFT value.
Letter C. Report confirmatory test with MPN value.
What does this indicate: If (+) gas:
a. Inoculate to EMB with MIS Technique
b. Report completed test with MPN value.
c. Report confirmatory test with MPN value.
d. Report confirmatory test with MTFT value.
Letter A. Inoculate to EMB with MIS Technique.
TRUE or FALSE
E.coli appear as purplish red colonies with green metallic sheen.
TRUE
TRUE or FALSE
In confirmatory test, incubate EMB plates at 34 C for 24-48 hours and observe growth colonies.
False. In completed test, incubate EMB plates at 34 C for 24-48 hours and observe growth colonies.
In completed test, after growth of colonies observed, what should you do next?
Gram stain and perform IMVC
Escherichia coli are positive in which part of IMVC?
a. Indole
b. Methyl Red
c. Voges-Proskauer
d. Citrate
Letter A and B . I and M
Klebsiella or Enterobacter are positive in which part of IMVC?
a. Indole
b. Methyl Red
c. Voges-Proskauer
d. Citrate
Letter C and D. V and C
Citrobacter are positive in which part of IMVC?
a. Indole
b. Methyl Red
c. Voges-Proskauer
d. Citrate
Letter B and D. M and C
Are media which can be used for presumptive stage
Lactose broth and Lauryl Sulfate Broth
Allows the growth of lactose fermenters
Lactose Broth and Lauryl Sulfate Broth
The strength of the broth depends on the water sample which will be analyzed:
___________ for treated water (chlorinated)
Double strength
The strength of the broth depends on the water sample which will be analyzed:
___________ for untreated water.
Single strength
The strength of the broth depends on the water sample which will be analyzed:
___________ treated & processed water (chlorination and other treatment processes)
Triple strength
Media used in the Multiple Tube Fermentation Method
BGLB (Brilliant Green Lactose Bile Broth
Inhibit gram-positive bacteria and many gram negative bacteria other than coliforms.
Ox-bile and Brilliant Green
A carbohydrate source in which the bacteria ferment lactose and produce gas are detected.
Lactose
Used for confirmation of presumptive positive tubes showing gas production in Lactose Broth or Lauryl sulfate.
BGLBB (Brilliant Green Lactose Bile Broth)
What does broth indicates?
Broth indicates a positive evidence of fecal coliforms.
Other non-fecal coliform bacterial also grow in this medium but mostly do not produce any gas.
BGLBB (Brilliant Green Lactose Bile Broth)
