XLD agar is used to isolate and identify pathogenic intestinal bacteria.
Composition g / l
Lactose 7.5
Saccharose 7.5
Yeast Extract 3.00
L-LEASIN 5.0
Xylose 3.5
Sodium Chloride 5.0
Deoxycholate of sodium 2.5
Sodium thiosulfate 6.80
Iron ammonium citrate 0,80
Phenol red 0.08
Agar-agar 15.00
Appearance:
A bottle of 500 g of dry medium.
Method of cooking:
Mix 56.7 g of dry medium in 1000 ml of distilled water. The mixture is boiled to the full
dissolving ingredients. , check the pH and, if necessary, adjust the values to 7.4 ± 0.2,
using a 10% solution of NaOH or a 10% solution of HCl. Sterilize in an autoclave at 121 ° C for
15 minutes. DO NOT AUTHORIZE THE ENVIRONMENT, DO NOT TRANSFERRED
THE ENVIRONMENT
Density of the finished medium:
The medium responsible for the density of 1.5% agar gel is formed.
Color and transparency of the finished environment:
The finished medium has a red color, transparent, slightly opalescent, if in Petri dishes then
gel is formed.
Acidity of the medium:
At 25 ° C, an aqueous solution (56.7% w / v) pH of 7.4 ± 0.2.
Principle and score of the result:
Used to isolate and identify pathogenic intestinal bacteria,
In particular, shigels, with faeces, are also used in the presence-absence test
Salmonella (2).
Deoxycholate suppresses the growth of gram-positive bacteria.
Nearly all enterobacteria, besides shigels, are fermented to xylose, which makes it possible to distinguish them.
from salmonella
Salmonella is fermentable with xylose, but at the same time it decarboxylates lysine, which,
Considering the return of pH to alkaline values, it can simulate the growth of shigella on
this environment.
However, to prevent such reactions in lysine-positive coliform bacteria, in
Wednesday in the abundance introduced lactose and sucrose. As a result of their fermentation
An acid is formed that prevents decarboxylation of lysine by non-pathogens
hydrogen sulfide-producing bacteria. Phenol red - an indicator of pH.
After inoculation of the medium by the test sample, it is placed in the incubator
for 18-24 hours at a temperature of 35-37 ° C.
Results
Microorganism Streams (ATCC) Rising Color
Escherichia coli (25922) Medium yellow
Enterobacter aerogenes (13048) Medium yellow
Proteus Vulgaris (13315) abundant yellow
Proteus mirabilis (25933) abundant yellow
Salmonella enteritidis (13076) abundant red with black
the center
Salmonella paratyphi A abundant red
Salmonella paratyphi In abundant reds with black
the center
Salmonellatyphi (6539) abundant red with black
the center
Salmonellatyphimurium (14028) abundant red with black
the center
Shigellasonnei (25931) abundant red
Shigella dysenteriae (13313) abundant red
