LMX Broth, Modified | Selective Medium for Coliform & E. coli Detection

LMX Broth, Modified

Chromogenic & Fluorogenic Medium for Coliform and E. coli Detection

Catalog Number: AS-1277

Overview

LMX Broth, Modified is a selective and differential liquid culture medium designed for the simultaneous detection and differentiation of total coliforms and Escherichia coli in water, food, beverage, and environmental samples.

Based on the original formulation developed by Kneifel and Manafi and later refined by Manafi and Ossmer, the modified formulation improves sensitivity, specificity, and ease of interpretation, allowing reliable detection of coliforms and E. coli within a single incubation step.

The medium incorporates both chromogenic and fluorogenic substrates, enabling clear visual results and rapid confirmation using UV light.

Key Features & Benefits

• Simultaneous detection of total coliforms and E. coli

• Chromogenic and fluorogenic system for clear result interpretation

• Blue-green colour change indicates coliform growth

• Blue fluorescence under UV light (365 nm) confirms E. coli

• Optimised formulation with enzyme substrates, tryptophan, and IPTG

• Suitable for routine water, food, beverage, and environmental testing

Principle of the Medium

LMX Broth, Modified combines selective agents and indicator substrates to support target organism growth while suppressing non-target flora:

• Phosphate buffers maintain optimal pH and support coliform growth

• Lauryl sulfate inhibits Gram-positive bacteria

• X-GAL (chromogenic substrate): produces a blue-green colour in the presence of coliform β-galactosidase

• MUG (fluorogenic substrate): yields blue fluorescence under UV light when hydrolysed by E. coli β-glucuronidase

• Tryptophan and IPTG: enhance enzyme induction and detection sensitivity

Typical Applications

Water Microbiology

• Drinking water and wastewater testing

• Surface and recreational water monitoring

Food & Beverage Microbiology

• Quality control testing of food and beverage products

• Environmental hygiene monitoring in production facilities

Environmental & Research Laboratories

• Screening of environmental samples for indicator organisms

• Research and method development studies

Composition (per litre)

• Tryptone: 5.0 g

• Sodium chloride: 5.0 g

• Sorbitol: 1.0 g

• Tryptophan: 1.0 g

• Dipotassium hydrogen phosphate: 2.7 g

• Potassium dihydrogen phosphate: 2.0 g

• Lauryl sulfate sodium salt: 0.1 g

• X-GAL: 0.08 g

• MUG: 0.05 g

• IPTG: 0.1 g

Final pH at 25 °C: 7.2 ± 0.2

Preparation (Single-Strength)

• Suspend 17 g of dehydrated medium in 1 L of distilled or purified water

• Heat gently with agitation until fully dissolved; avoid overheating

• Dispense into suitable tubes or flasks

• Sterilise by autoclaving at 121 °C for 15 minutes

• Cool to room temperature and protect from light

• Inoculate aseptically and incubate at 35–37 °C for 18–24 hours

Result Interpretation

• Coliforms: Medium changes from yellow to blue-green

• E. coli: Blue-green medium with blue fluorescence under UV light (365 nm)

Storage & Stability

• Dehydrated medium: Store at 2–8 °C, dry, protected from moisture and light

• Prepared medium: Store at 2–8 °C, protected from light; use within recommended shelf life

Intended Use

For laboratory use only, including water, food, beverage, environmental testing, and research applications.

Not for human or veterinary use.

Quality & Compliance

• Manufactured under controlled conditions for batch consistency

• Performance aligned with internationally recognised chromogenic and fluorogenic coliform/E. coli media

• Suitable for routine quality control and regulatory testing workflows

Customs & Trade Information

HS / AHECC Code: 3821.00.00
Prepared culture media for development or maintenance of microorganisms