Question

KIA (Kligler Iron Agar) Slant KIA is the most complex media described in this exercise, and it is essential that you use the lab manual and the relevant videos for support when interpreting KIA results. KIA medium contains both the carbohydrates glucose and lactose, in a 1:10 ratio. I addition to the carbohydrates, the media also includes peptones, as an alternative energy source. This media results reveals use of both carbohydrates independently, plus the use of protein (peptones). The KIA medium also contains the pH indicator phenol red.

If an organism can utilize both glucose and lactose, which will be used first? Why?

When an organism used to inoculate a KIA slant can utilize glucose, a limited amount of acid will be produced. This is due to the limited amount of glucose in the media.

If KIA includes the pH indicator phenol red, what color will it turn when an organism breaks down glucose in the media?

Answer 1

Klinger's Iron Agar medium is a differential media used to differentiate members of Enterobactericeae family based on production of hydrogen sulphide and carbohydrate fermentation. KIA media contain four protein sources; beef extract, yeast extract, peptone, proteose protein. The media contain two carbohydrate sources glucose and lactose. Ferrous sulfate is the hydrogen sulphide detector and phenol red is pH indicator. Sodium thiosulfate act as source for Sulphur.

The KIA distinguish organism based on the ability to use the sugars glucose or lactose. The organism can be differentiated as glucose fermenting or lactose fermenting. Glucose and lactose are distributed evenly throughout the slant and butt. But lactose is present in a concentration of 10 times that of glucose. Glucose and lactose utilisation by organisms can be detected by colour change. The red colour of media turns to yellow when organism ferment sugars and produce acid. The phenol red detect the colour change.

The yellow slant and yellow butt indicates lactose and glucose fermenter. Red slant and yellow butt indicates glucose positive and lactose negative.

1. If an organism can utilize both glucose and lactose, the organism first utilise Glucose. Because only 1% of glucose is present and also glucose is a simple sugar to taken by organisms. After complete fermentation of glucose, organism then utilise lactose which is a more complex carbohydrates than glucose . Lactose is present 10 times the concentration of glucose. The organism that can ferment both Glucose and Lactose gives Acid Slant/ Acid butt ; yellow slant and yellow butt.

2. The KIA media incorporated with phenol red indicator have a red colour. The fermentation of glucose produces acid, the pH of media lowers to acidic and red colour of pH indicator phenol red turns to yellow. The acidic end products change the red colour of media turns to yellow.