This medium was developed for use with the Most Pro
bable Numbers Technique (M.P.N.) for the enumeratio
n of coliforms in water
supplies. The medium is an improved version of the
chemically defined glutamic acid medium described b
y Gray in 1964. The product is
supplied in two parts because it has been shown tha
t separating the sodium glutamate from the base imp
roves its stability.
Calcium chloride (CaCl
Dipotassium hydrogen phosphate
Glutamic acid (sodium salt)
Method for reconstitution
Dissolve 22.7 grams of base medium (LAB 80a) togeth
er with 12.7 grams of sodium glutamate (LAB 80b) in
1 litre of
deionised water containing 5 grams of ammonium chlo
ride eg BDH cat no. 27149. Dispense 10ml and 50ml v
olumes into tubes with
inverted Durham tube.
Dissolve in 11.35 grams of base medium (LAB 80a) to
gether with 6.35 grams of sodium glutamate (LAB 80b
) in 1 litre
of distilled water containing 2.5 grams ammonium ch
loride. Dispense 5ml volumes into tubes with invert
ed Durham tubes.
by autoclaving for 10 minutes at 115°C, alternative
ly heat to 100°C for 30 minutes on three successive
Purple, clear solution.
6.7 ± 0.2
Minimum Q.C. organisms:
Storage of Prepared Medium:
Capped containers – up to 3 months at 15-20°C in th
Use the Most Probable Number technique. With 10ml a
nd 50ml of sample add to equal volumes of double st
With 1ml volumes of sample add to 5ml of single str
ength medium. Ensure the Durham tube is free of bub
37°C for 18-24 hours aerobically.
Tubes showing the production of acid (medium turns
yellow) and gas in the Durham’s tube are considered
positive. Each presumptive positive tube should be
subcultured to Brilliant Green Bile Broth LAB 51 wi
th Durham tube and incubated at
44°C for 24 hours and examined for gas production.
A tube of Tryptone Water LAB 129 should also be ino
culated and incubated at 44°C
for 24 hours for the production of indole. The prod
uction at 44°C of gas from lactose and the formatio
n of indole are evidence of
Gray, R.D. (1964). An improved formate lactose glut
amate medium for the detection of
and other coliform organisms in water. J. Hyg.
Camb. 62: 495-508.
PHLS Water Sub-Committee. (1958). A comparison betw
een MacConkey broth and Glutamic acid media for the
detection of coliform organisms in water. J.
Hyg. Camb. 56: 377-388.
PHLS Standing Committee on Bacteriological Examinat
ion of Water Supplies. (1968). Comparison of MacCon
key Broth, Teepol Broth and Glutamic Acid
Media for the enumeration of Coliform organisms in
water. J. Hyg. Camb. 66: 67-87.
Environment Agency: The Microbiology of Drinking Wa
ter (2002). Methods for the Examination of Water an
d Associated Materials.