Water microbiology Part 3 Flashcards
Described as all facultative anaerobic gram-negative, nonspore forming, rod shaped bacteria that ferment lactose with gas and and acid formation within 48 hrs at 35 C
Coliform bacteria
Determine the efficiency of treatment plant operation and the intergrty of the distribution system?
Total coliform test
Example of distribution system?
pipes
NOTE: Any amount of Coliform is contamination
What is the method in multiple tube fermentation that uses nutrient rich medium that detects and estimates the coliforms
Tube dilution method
What is the unit or to report the result?
MPN (Most probable number)
Water treatment = Coliform Count
An Estimate of the Mean density of coliforms? (Density)
Most probable number
NOTE: Turbidity shows the density of the bacteria
What distribution is used in MPN?
Poisson distribution
What are the 3 Phases of MTFT?
Presumptive
Confirmed
Completed
What is used in Confirmed phase?
Total coliform count
What is used in Completed phase?
Thermotolerant coliform count
What media is used in Presumptive phase?
Lauryl tryptose broth
What is the pH for Lauryl tryptose broth?
6.8+-0.2
What are the alternative for Lauryl tryptose broth?
Lauryl sulfate broth
If none
Lactose broth
What is the tube that is inverted in Lauryl tryptose broth?
Durham tube
How to determine the LTB strenght?
By adding water (100, 20, 10 mL) to the medium
What is the ratio for Triple strength LTB for sample?
10mL Triple strength LTB for 20mL of sample
Ex. 5g/10mL + 20 mL sample = 5g/30mL (Need adjustment )
15g/10mL + 20mL sample = 15g/30mL
Procedure for Presumptive in MTFT?
- Use Lauryl tryptose broth then determine the Triple strength of LTB
- Arrange fermentation tubes in row of five
- Mix the sample by shaking the bottle for about 25 times
- Inoculate each tube with 20 mL water sample portions
Procedure for Presumptive in MTFT?
- Use Lauryl tryptose broth then determine the Triple strength of LTB
- Arrange fermentation tubes in row of five
- Mix the sample by shaking the bottle for about 25 times
- Inoculate each tube with 20 mL water sample portions
- Mix test portions in the medium by gentle agitation
- Incubate at 35 +- 0.5 (24 hrs: turbid, gas and acid reaction / 48 hrs)
- Examine the turbidity, gas production and acidic reaction
What is the positive indicator for Multiple tube fermentation technique?
Presence of growth, Acid, and gas
NOTE: Tubes that are Positive are submitted to the confirmed phase
What media is used in confirmed test?
Brilliant green lactose bile broth with inverted durham tube
What is the pH for Brilliant green lactose bile broth?
pH 7.2+-0.2
Process for confirmed phase?
- Use BGLB with inverted durham tube
- Gently shake the tubes to re-suspend the organism
- Transfer one loopful of the culture from LTB to BGLB broth
- Do this in all presumptive test
- incubate at 35+-0.5C
- Check the result and calculate the MPN value those who are positive
What is the size in diameter for sterile loop?
3.0 - 3.5 mm
Positive indicator for Confirmed phase?
Formation of gas or turbidity within 48 hrs +- 3 hrs
What is the Media used in Completed phase?
EC (E. coli) broth / EC-MUG
What is the ph for EC broth?
6.9+-0.2
NOTE: The process of Completed phase is similar to Confirmed phase (Except incubation)
What is the temp for incubation for completed phase?
44.5 +- 0.2
What is the positive indicator for Completed phase
24 hrs +- 2hrs = Gas formation
What is the incubation equipment used in Completed phase?
Water bath
Summarize the MPN value from the MPN Table
0 = <1.1 MPN/100mL
1 = 1.1 MPN/100mL
2 = 2.6 MPN/100mL
3 = 4.6 MPN/100mL
4 = 8.0 MPN/100mL
5 = >8.0 MPN/100mL
MPN value if the value is <1.1 MPN/100mL
Absence
MPN value if the value is >1.1 MPN/100mL
Presence
If the results for HPC, Total coliforms and Fecal coliforms are all within the standards for quality water; the final remark reported is?
Passed
