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What is the presumptive test in analysis for potable water?
inoculation into lauryl tryptose broth tubes
What are the results for the presumptive test in analysis for potable water?
production of gas after incubation at 37 °C for 24-48h
What is the confirmed test in analysis for potable water?
inoculation into brilliant green lactose bile broth or streak culture on EMB agar
What are the results for the confirmed test in analysis for potable water?
gas after 48±3h/37±0.5 °C, typical coliform colonies after 24h/37 °C
Why is the confirmed test done after a presumptive test?
positive results may be from Clostridium or Bacillus
What is the completed test in analysis for potable water?
inoculation into lauyrl trptose broth and gram-stain
What are the results for the completed test in analysis for potable water?
gram-negative, nonsporeforming bacilli, production of acid and gas from lactose fermentation
Which coliform is the more reliable sewage indicator and why?
E. coli because Enterobacter can be isolated from soil and grains
How is Endo medium used to identify coliforms?
aldehydes from coliform breakdown of lactose react with basic fuchsin to form metallic green sheen
What identifies total coliforms?
ferment lactose + acid/gas in 48h/35 °C, green colonies on Endo in 24h/35 °C
What identifies fecal coliforms?
ferment lactose + acid/gas, blue colonies on m-FC in 24±2h/44.5±0.2 °C
What advantages are there to the membrane filter test in analysis for potable water?
greater sensitivity, larger volumes tested, higher degree of reproducibility, shorter time
What disadvantages are there to the membrane filter test in analysis for potable water?
filter can be plugged by cyanobacteria or extraneous debris
Which organisms from Exp. 7 grow on EMB agar?
E. coli (green), S. typhimurium (colourless), P. aeruginosa (colourless), C. freundii (red)
Which organisms from Exp. 7 grow on Endo agar?
E. coli (green), S. typhimurium (pink), P. aeruginosa (red), C. freundii (green)
Which organisms are not lactose fermentors from Exp. 7?
B. subtilis, S. aureus, S. typhimurium, P. aeruginosa
What does the Indole test do?
presence of tryptophanase to break down tryptophan into pyruvic acid, ammonia & indole
What is the procedure for the Indole test?
inoculation into tryptone broth, add Kovac's reagent to react with indole
What does the Voges-Proskauer test do?
presence of acetylmethylcarbinol (acetoin) from sugar fermentation
What is the procedure for the Voges-Proskauer test?
inoculation into MRVP tubes, add KOH+alphanaphthol, wait 20 min
What is the procedure for the Citrate test?
inoculation into sodium citrate slant with bromothymol blue
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