Total Coliform and Ecoli Flashcards
Length of time for record retention - Microbiology
5 years
How is sunlight an interference
may hydrolyze indicator compounds resulting in a false positive
Bleach concentration for sample collection
1 oz per gallon
Shelf life of raw TSB media
unopened - 2 years
opened - 6 months (1 year in dessicator)
TSB weight/ volume prep ratio
30 +/- 0.01g to 1000 mL DI water
TSB autoclave time and temp
119-121*C 12-15 min on slow
must NOT sit in autoclave for more than 45 min from door closing
final pH of TSB
7.3 +/- 0.2
shelf life of prepared TSB pre sterilization
3 months R, 1 week RT
Sterilization of Neg Control Water
119-121*C for 30 min on slow
Sample Collection steps
Flush tap for about 1 min
Sanitize tap for about 2 min
Fully open and flush tap for 3-5 min
Take chlorine reading (free and total)
Aseptically collect sample
What is the preservative used to remove chlorine?
Sodium Thiosulfate
Maximum holding time for Bacteria samples
30 hours refrigerated
Volume/ headspace of collection
100 mL with 1 inch of headspace
Over 100 mL sample?
Under 100 mL sample?
over - aseptically adjust volume to 100 mL
under - sample rejected due to insufficient volume (re-collect)
For potable bacteria samples, Colilert or Colisure?
Colisure
What is a sample set defined as?
up to 60 samples who have an inclusive incubation time of 4 hrs, with one POS and one NEG control
After the addition of Colisure, how long can samples sit prior to incubation?
30 min
Incubation temp and time
35.0 +/- 0.5 *C
Colilert- 24 to 28 hrs
Colisure- 24 to 48 hrs
Colisure result interpretations for Total Coliform:
No Color Change - Neg. for Total Coliform
Color Change - Yellow to Magenta, Pos. for total Coliform
Colisure result interpretations for E. Coli:
No Fluorescence - Neg. for E. Coli
Fluorescence - Pos. for E. Coli
Analyst QC requirements
Certified analysts are required to preform test at least once a month
Total number of bottles for TSB sterility check
1%, no more than 4
Autoclave time and temp for contaminated bacteria materials
119-121*C for 45 min
Autoclave sterility testing is required how often and by what method?
once every 3 months, by either commercially manufactured check solution or by TSB inoculation
What does TSB stand for?
Tryptic Soy Broth
How often should thermometers be calibrated?
annually
How often should timers be calibrated?
every three months
pH linearity acceptance criteria
-56 to -62 mV
