FINALS: Microbiology of Water (Lab) Flashcards
This serves as excellent nutritional sources for the growth and multiplication of microorganisms
Vast amounts of organic matter in polluted waters
These diseases or intestinal infections are acquired from (polluted) water
- bacillary dysentery
- typhoid fever
- cholera
- paratyphoid fever.
About 3.4 million deaths annually are caused by dangerous waterborne enteric bacterial pathogens such as
- Shigella dysenteriae
- Campylobacter jejuni
- Salmonella typhi
- Vibrio cholerae
SSCV
In addition to bacterial infections, unsafe water supplies are responsible for numerous parasitological infections, including helminth diseases such as
schistosomiasis and especially guinea worm (Dracunculus medinensis)
(Few) Parasitic protozoa responsible for major diarrheal disease in humans
- Balantidium coli
- Entamoeba histolytica
- Giardia intestinalis
(formerly called G. lamblia)
BEG
In addition to bacterial infections, unsafe water supplies also causes intestinal, hepatic, and pulmonary flukes, including:
- Fasciolopsis buski
- Clonorchis sinensis
- Paragonimus westermani
The bacterium that indicates fecal pollution
Escherichia coli
This bacterium is always present in the human intestine, its presence in water alerts public health officials to the possible presence of other human or animal intestinal pathogens
E. coli
TRUE OR FALSE: In the tropics and subtropics E. coli is not considered a reliable indicator of fecal pollution because the soil in these regions naturally contains high levels of E. coli
TRUE.
E. coli is present
in the water anytime there is ________?
surface runoff
Both ________ and ________ methods are used to determine the sanitary condition of water
qualitative; quantitative
The three basic (Qualitative) tests to detect coliform bacteria in water are:
- Presumptive test
- Confirmed test
- Completed test
TRUE OR FALSE: Presumptive, confirmed, and completed tests are not performed sequentially on each sample under analysis
FALSE. They are performed sequentially
on each sample under analysis
IDENTIFY: These are indicators of fecal contamination, are gram-negative, non– spore-forming bacilli that ferment lactose with the production of acid and gas
Coliform bacteria
Coliform bacteria is detectable following a __________ incubation period at _____.
24-hour; 37°C
This is only for detection of coliform bacteria. Measure aliquots of the water to be tested are added to a lactose fermentation broth containing an inverted gas vial.
presumptive test
Why is lactose fermentation broth used for detecting coliform bacteria?
Because COLIFORM bacteria are capable of using lactose as a carbon source (the other enteric organisms are not)
In this experiment, you will use lactose fermentation broth containing an inverted Durham tube for gas collection.
Presumptive test
Tubes of the lactose medium are inoculated with?
10-ml, 1-ml, and 0.1-ml aliquots of the water sample
In the presumptive test, aliquots of water are tested in a lactose fermentation broth, it is composed of ________, and each of this contains at least _______.
3 groups; 5 tubes
What do we observe in the presumptive test?
Gas formation
What are the positive and negative results in the presumptive test?
Positive: Gas in fermentation tube
Negative: No gas in fermentation tube
This/These are singe-strength lactose broth
Groups with 1.0 mL and 0.1 mL aliquots of water sample
This/These are double-strength lactose broth
Group with 10 mL aliquot of water sample
Incubation time for the Lactose fermentation broth with aliquots of water
48 hours at 37°C
This test confirm the presence of enteric microorganisms
Confirmed test
TRUE OR FALSE: In the presumptive test, the greater the number of tubes per group, the greater the sensitivity of the test.
TRUE
This is presumptive evidence of the presence of coliform bacteria in the sample
Development of
gas in any of the tubes
This is estimated by determining the number of tubes in each group that show gas following the incubation period
most probable number (MPN)
This test requires that selective and differential media (e.g., eosin methylene blue (EMB) or Endo agar) be streaked from a positive lactose broth tube obtained from the presumptive test
Confirmed test
This medium contains the dye methylene blue, which inhibits the growth of gram-positive organisms. In the presence of an acid environment, it forms a complex that precipitates out onto the coliform colonies, producing dark centers and a green metallic sheen
Eosin–methylene blue
This reaction on EMB is characteristic for
Escherichia coli, the major indicator of fecal pollution
dark centers and a green metallic sheen
A nutrient medium containing the dye fuchsin, which is present in the decolorized state
Endo agar
In Endo agar, the presence of _____ is produced by
the coliform bacteria, ____ forms a dark pink complex that turns the E. coli colonies and the surrounding medium pink
acid; fuchsin
TRUE OR FALSE: Positive presumptive test may be due to noncoliform origin
TRUE
Incubation time in Confirmed test:
24 hr at 37°C
Positive confirmed test:
Typical coliform
colonies, water
nonpotable
Negative confirmed test:
No coliform colonies, water potable
The final analysis of the water sample. It is used to examine the coliform colonies that appeared on the EMB or Endo agar plates used in the confirmed test.
Completed test
In the completed test, colony from the confirmatory test plate is inoculated into a tube of __________ and streaked on a _____________ to perform a Gram stain
lactose broth; nutrient agar slant
Several testing methods are available for testing for safe water including:
- Most probable numbers (MPN)
- ATP testing
- Membrane filtration
- Use of pour plates
NagkaMAMU
In the complete test, if gas is produced, the next step is?
Prepare gram stain from the slant
It is a quantitative analysis and is used for counts of total coliforms, fecal coliforms, and E. coli
Most probable number (MPN)
This has the ability to inoculate greater amounts of sample, has higher sensitivity than plate count method, and is versatile
Most probable number (MPN)
Incubated at 35°C for 24 hours and is checked for growth/ gas production
Lauryl Sulphate Tryptose (LST)
Selective medium for total coliforms and is checked for growth/ gas production
Brilliant Green Broth (BGB)
This broth inhibits noncoliforms and contains lactose and 2% bile
Brilliant Green Broth (BGB)
Presumptive evidence of coliform contamination in LST:
Bubble in the Durham tube
Bubbles in Durham tube indicates?
Gas production
This is verified by turbidity or cloudiness
Growth
Confirmation of coliform contamination in BGB:
bubble in the Durham tube
In the quantitative analysis of water, bacteria-tight membrane filters is capable of retaining microorganisms larger than _______ are frequently used for analysis of water.
0.45 micrometer (µm)
Advantages of bacteria-tight membrane filters
(1) results are available in a shorter period of time
(2) larger volumes of sample can be processed, and
(3) because of the high accuracy of this method, the results are readily reproducible.
In the membrane filter method, trapped microorganisms are transferred in _______ containing ________
Petri dish; absorbent pad
In the membrane filter method, this determines the potability of water
Total count of coliform bacteria
In membrane filter method, you aseptically place an absorbent pad in a ______ petri dish.
50-mm
It is customary to ____ heavily polluted samples, thereby reducing the number of cells collecting on the membrane
dilute
What agar is used in the membrane-filter method?
Endo agar
Formula for total colony count:
colony count x dilution factor /ml of sample used x 100
Steps or procedure in the quantitative analysis of water
Special porous membrane ->
Trap microorganisms -> Endo agar ->
Coliform growth (red or metalic colonies)
Presumptively identifies Enterobacteriaceae and verotoxin producing E. coli
4- Methylumbelliferyl- B-d- Glucuronide (MUG) Test
Reagent used for MUG test
4- Methylumbelliferyl-B-d-glucuronide
Substrate in the MUG test
B-d-glucopyranosid-uronic
Enzyme in the MUG test
B-d-glucuronidase
B-d-glucopyranosid-uronic is split/derivatives to:
Aglycons & D-glucuronic acid
End product in the MUG test
4-methylumbelliferyl moiety
MUG test positive result
Electric Blue fluorescence observed in 366-nm UV
Differentiates microorganisms based on metabolic reaction in litmus milk
Litmus Milk Medium
Litmus Milk indicator
Litmus dye
Appearance of Indicator (Litmus Dye): Pink, mauve
pH Change to- Acid
Record- Acid (A)
Appearance of Indicator (Litmus Dye): Purple
pH Change to- No change
Record- No change
Appearance of Indicator (Litmus Dye): White
pH Change to- Independent of pH change; result of reduction of indicator
Record- Decolorized
Appearance of Indicator (Litmus Dye): Blue
pH Change to- Alkaline
Record- Alkaline (K)
In Litmus milk, Coagulation or clot occurs when pH is:
Indicate record as well
Acid or alkaline
Record: clot
In Litmus milk, dissolution of clot with grayish, watery fluid and a clear, shrunken, insoluble blue clot occurs when pH is:
Indicate record as well
Alkaline
Record: Peptonization
In Litmus milk, dissolution of clot with grayish, watery fluid and a shrunken, insoluble pink clot occurs when pH is:
Indicate record as well
Acid
Record: Digestion
