21 - Drinking water analysis

Describe KF strep agar, including

• what it tests for

• selective, differential, or both

• main differential component

• Enzyme of pathway product

• pos controls

• streptococcus and enterococcus species, uses membrane filiter techique that traps organissm larger than .45um

• selective against organisms with ETC, differential makes enterococcus red

• Sodium azide inhibits org. with ETC, 1% TTC gives red color to enterococcus species

• appears red - enterococcus

What are the characteristics of coliforms?

ferment lactose to acid and gas, gram negative, non-spore forming bacilli

Describe LST-MUG Test, including

• what it tests for

• the media

• selective, differential, or both

• main differential component

• Enzyme of pathway product

• positive control

• negative controls

• tests for cleaving of MUG to MU (Indicates E coli), growth and fermentation of sugar

• lauryl tryptose broth

• differential, indiciates MUG to MU under fluorescent light

• MUG and lactose in broth

• MUG to MU by GUD enzyme

• Escherichia coli, gas in tube, growth, blue under fluorescent light

• Klebsiella Pnuemoniae (yellow in UV), Proteus Vulgaris (yellow in UV)

Describe EMB agar, including

• what it tests for

• selective, differential, or both

• main differential component

• Enzyme or pathway product

• positive controls

• E coli

• selective for gram negatives, differntial for sugar fermentation

• dyes inhibit growth of gram positives and dyes bacteria

• fermentation of sugars

• Escherichia coli - appear metallic green, lactose ferm and acid production

• klebsiella pneumoniaea - purplish, growth no fermentation or acid production

• Proteus vulgaris - pinkish, no lactose fermentation but some acid production

What does the membrane filter do when getting coliforms from water samples?

traps organisms larger than .45um

What color do fermentative bacteria that produce some but not a lot of acid appear on EMB agar? Give an example

pink, Proteus vulgaris

What color do non-fermentative bacteria appear on EMB agar? Give an example

purple, Klebsiella pneumoniae

What genus of organisms can grow on KF strep agar?

streptococcus and enterococcus species

What are the controls for EMB agar and what do their results indicate?

• Escherichia coli - appear metallic green, lactose ferm and acid production

• klebsiella pneumoniaea - purplish, growth no fermentation or acid production

• Proteus vulgaris - pinkish, no lactose fermentation but some acid production

What is EMB agar usually used for?

differentiating between E. coli, lactose-fermenting, and non-lactose-fermenting gram-negative bacteria based on their colony appearance; fecal contamination confirmatory test