Lactose Broth

Description

It is commonly used with Durham fermentation tubes for the detection of gas formation. If a specific volume of sample is to be inoculated, this must be taken into consideration when making up the medium, as the concentration must not be altered on addition of the inoculum.

Although it is not Eijkman's original formulation, this broth provides excellent results in assays of gas production at 44 ± 1 °C, which is a characteristic of Escherichia coli.

While preparing this medium it is important to avoid overheating and to distribute it into tubes before sterilization.

Technique

To inoculate tubes, follow the standard laboratory methods or the applicable norms (stab inoculation, loop inoculation, dilution banks, Most Probable Number (MPN) technique, pipette inoculation, etc.).

It is possible that air bubbles are generated in the Durham tube during the transport. If air bubbles are present in the Durham tube prior to inoculation, the tube should be inverted until the air is released from the Durham tube. Failure to remove air bubbles prior to inoculation may result in reading the result as a false-positive reaction in gas production.

LC-5013, 125 mL bottles

Although it is not Eijkman's original formulation, this broth provides excellent results in assays of gas production at 45 °C, which is a characteristic of Escherichia coli.

Collect, dilute and prepare samples and volumes as required according to specifications, directives, official standard regulations and/or expected results.

Dispense liquid medium in appropriate containers if the original container is of large volume.

Add to each tube a glass Durham tube before incubation to study superfermentation when used as a medium for coliform detection.

Inoculate aseptically the tubes with the prepared sample or its dilution.

Incubate the tubes tightly closed aerobically at 35-37 °C for 24 hours when used as pre-enrichment broth.

Read the turbidity increase as growth indicator.

(Incubation times, temperature and sample volumes may vary depending on the sample or on the specifications.)

Each laboratory must evaluate the results according to their specifications.

LC-5069, 60 mL bottles

Medium used for confirmation of coliform capacity based on lactose fermentation.

Medium used for previous pre-enrichment in various microbiological methods.

Use the medium according to intended purpose, samples and validated methods using aseptic technique.

Incubate at 35 ± 2.0 °C for 24 ± 2 h.

Positive identification by turbidity and gas production.

Physical/chemical control

Microbiological control

Inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity).

Microbiological control according to ISO 11133:2014/Amd 1:2018.

Aerobiosis. Incubation at 35 ± 2 °C. Reading at 24 hours.

LC-5013, 125 mL bottles: microbiological control

Prepare tubes with Durham bell - inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity) / 10⁴-10⁶ CFU (selectivity).

Add an inverted Durham bell into each tube.

Aerobiosis. Incubation at 35 ± 2 °C, reading at 24-48 hours.

Microbiological control according to ISO 11133:2014.

LC-5069, 60 mL bottles: microbiological control

Prepare tubes - inoculate: practical range 100 ± 20 CFU; min. 50 CFU (productivity).

Add an inverted Durham bell into each tube.

Aerobiosis. Incubation at 35 ± 2 °C. Reading at 24 hours.

Sterility control

Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.

Check at 7 days after incubation in same conditions.

• APHA-AWWA-WPCF (1998) Standard methods for the examination of water and wastewater. 20th ed. APHA Washington.
• DOWNES, F.P. & K. ITO (2001) Compendium of Methods for the Microbiological Examination of Foods. 4th ed. APHA. Washington.
• FDA (Food and Drug Administration) (1998) Bacteriological Analytical Manual 8th ed. Rev A. AOAC International. Gaithersburg. VA. USA.
• ISO 9308-2 Standard. (1990) Water Quality - Detection and enumeration of coliform organisms, thermotolerant coliform and presumptive E. coli - MPN technique.
• ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
• ISO 21150:2006 Standard. Cosmetics - Detection of Escherichia coli.
• US PHARMACOPOEIA (2005) <61> Microbial limit test. US Pharmacopeial Conv. Inc. Rockville. MD. USA.
• VANDERZANT & SPLITTSTOESSER (1992) Compendium of Methods for the Microbiological Examination of Foods. 3rd ed. APHA. Washington.