water

Question 1

The most common and inexpensive method of
bacteriological analysis of water is done using the

Answer 1

MPN
method otherwise known as the multiple-tube fermentation
technique (MTFT)

Question 2

This method cultures water using several tubes in
dilution. Nutrient-rich medium is utilized to detect and
estimate the total coliforms in a given volume of water
sample

Answer 2

MPN METHOD

Question 3

dest but
cheapest method of bacteriological testing for
water sample

Answer 3

o Multiple tube techniques:

Question 4

where erial dilutions
of water sample are filtered using vacuum.

The
recommended pore size of membrane filter to use
is 0.45 micron.

Answer 4

Membrane-filtration techniques: S

Question 5

Several dilutions of water sample in
melted nutrient agar are poured in bottles,
solidified in slopes, sealed and incubated

Answer 5

Pour plates:

Question 6

Colonies that grow in the slope are counted
visually as_______

The total
number of colony forming units referred to as the
___________________s calculated by
multiplying the number of colonies with the dilution
used

Answer 6

Colonies that grow in the slope are counted
visually as colony forming units (CFU).

The total
number of colony forming units referred to as the
Total viable count (TVC) is calculated by
multiplying the number of colonies with the dilution
used

Question 7

Multiple tube Fermentatio

Answer 7

Presumptive Phase
o Mix sample by making 25 complete up and down
or back and forth movements in 7 seconds.
o With a sterile 20 ml pipette, inoculate 20 ml of
water sample into each 5 tubes of primary lauryl
tryptose broth. Shake gently to distribute the
sample uniformly throughout the medium.
o Incubate the tubes at 35 +/- 0.5°C for 24 hours.
After the end of the 24-hour incubation period,
examine each tube for the presence of gas. If
present, gas can be seen in the Durham tube, if
none is visible, gently shake the tube, if any
effervescence (stream of tiny bubbles) is
observed, the tube should be considered positive.
Enter the number of tubes in a table.
o If no gas has developed, reincubate the tubes for
another 24-hour period. At the end of this period
check the tubes again for gas production. Enter
the number of positive tubes in the table. If still
there’s no gas produced, release as negative for
coliforms.

Question 8

” refers to a large group of Gram-negative, rod-shaped bacteria that share several
characteristics.

Answer 8

“total coliforms

Question 9

has been used in water
microbiology to denote coliform organisms which grow at
44 or 44.5 C and ferment lactose to produce acid and gas.

They are provisionally identified by the production
of acid and gas from the fermentation of lactose

Answer 9

“faecal coliform”

Question 10

Nutrient-rich environments may encourage the
growth or persistence of some species of
thermotolerant coliform other than E. coli.

Answer 10

environment

Question 11

The presence of faecal streptococci is evidence of faecal
.

Answer 11

contamination

Question 12

Two techniques are commonly used to detect the presence
of coliforms in water.

Answer 12

1. multiple fermentqation tube
2. membrane filter etchnique

Question 13

It is customary to report the results of the multiple
fermentation tube test for coliforms as a most probable
number

Answer 13

(MPN) index

Question 14

Dehydrated powder, packaged in pre-weighed
amounts suitable for making one batch of medium, to
be dissolved in an appropriate volume of distilled water,
dispensed to culture tubes and sterilised before use.

Answer 14

Dehydrated powder,