Lactose Broth

EMD Cat. No. 1.07661.0500
500 g


Inhibitor-free culture medium used as a preliminary test for coliform bacteria, especially E. coli.

The composition of this medium complies with the recommendations of the American Public Health Association for the examination of water (1998) and foodstuffs (1992), and with the recommendations of the United States Pharmacopeia XXIII (1995) and the European Pharmacopeia II for the examination of pharmaceutical products and raw materials.

Mode of Action Preparation
Experimental Procedure and Evaluation Quality Control
Typical Composition (g/liter) Literature


Mode of Action
 Lactose utilization is indicated by gas production. The gas liberated is collected in DURHAM tubes.


Typical Composition (g/liter)
 Peptone 5.0; meat (beef) extract 3.0; lactose 5.0.

Preparation
 Suspend 13 g or more in 1 liter of purified water (see Table), dispense into test tubes fitted with DURHAM tubes, autoclave (15 min at 121°C).
 pH: 6.9 ± 0.2 at 25°C.
 The prepared broth is clear and yellowish.

Experimental Procedure and Evaluation
 Mix 1, 10 or 100 ml samples with the specified volumes of lactose broth. The initial concentaton of the lactose broth must be increased so that the final concentration of the components is maintained at a constant level (13 g/l). See table.

Inoculum
 (ml)
 		Amount of
 Medium
in Tube
 ml
 		Volume of
 Medium +
 Inoculum
 ml
 		Dehydrated
 Lactose Broth
 Required
 g/L
 		Broth
concen-
 tration
           1
 		10 or more
 		11 or more
 		13
 		   1-fold
         10
 		10
 		  20
 		26
 		   2-fold
         10
 		20
 		  30
 		  19.5
 		1.5-fold
       100
 		20
 		120
 		78
 		   6-fold
       100
 		50
 		150
 		39
 		   3-fold


Incubation: 24-48 hours at 35°C aerobically.
 Check the DURHAM tubes for gas production.

Quality control

Test strains
 Growth
 		Gas formation
Escherichia coli ATCC 8739
 		good / very good
 		+
Klebsiella pneumoniae ATCC 13883
 		good / very good
 		+
Salmonella typhimurium ATCC 14028
 		good / very good
 		-
Proteus vulgaris ATCC 13315
 		poor / fair
 		-




Literature

American Public Health Association: Compendium of methods for the microbiological examination of foods. - 3rd. ed., 1992.
 American Public Health Association: American Water Works Association and Water Pollution Control Federation: Standard Methods for the Examination of Water and Wastewater 20th ed., Washington, 1998.
 European Pharmacopeia II, Chapter VIII, 10.
 United States Pharmacopeia XXIII, Chaptre "Microbiol. Limit Test", 1995.



© 2002 Merck KGaA, Darmstadt, Germany