Lab 15: Fecal Coliform Determination in Surface Water

define coliform and give an example

can ferment lactose, Escherichia coli

define non-coliform and give an example

cannot ferment lactose, Salmonella

what specific sugar is in the media used for the presumptive test?

lactose

if you have any gas bubbles that were trapped in your lactose broths, what does this indicate? what specific gas are the bacteria producing?

bacteria is capable of fermenting lactose, CO2

what is the name of the inverted test tube found in the DSLB & SSLB test tubes?

Durham test tube

why is E.coli a good sewage indicator? be sure to include three reasons

1. is not found in soil

2. easy to grow in laboratory conditions

3. survives a short time out of the body

what is the selective for EMB?

eosin prevents gram positive

what is the differential for EMB?

blue/black colonies with green sheen

other coliforms = pink colonies

non-coliforms = colorless

is the right or left positive for E.coli?

left

what is selective for Endo?

fuschin inhibits gram positive

what is the differential for Endo?

dark red colonies sometimes with green sheen

non-coliforms  = colorless

is the right or left positive for Salmonella sp.?

right

is the right or left positive for E.coli?

right

is the right or left positive for Salmonella sp.

left

what is the purpose of the Durham test tubes?

to collect CO2

presumptive test

designed to screen large numbers of samples quickly

confirmed test

designed to test for the presence of gram negative bacteria

inoculate 10ml, use 10ml pipette

fill to the 0

inoculate 1 ml, use 1 ml pipette

fill to the 0

inoculate 0.1 ml, use 1 ml pipette

fill to the 0.9