M-Endo Coliform Broth
M-Endo is a red colored media, which needs to be stored in the dark to prevent discoloration. Gram-positive bacteria are inhibited on this media by the desoxycholate and lauryl sulfate. The addition of ethanol increases the antibacterial nature of the formulation. Lactose fermenting organisms form aldehydes, which react with Schiff’s reagent (basic fuchsin and sodium sulfite) to give red colored zones around the colonies. Coliform colonies are therefore red with a characteristic metallic sheen.
MI Broth and MI Agar
MI Broth detects the presence of coliform bacteria by the production of b-galactosidase, which cleaves the substrate MUGal to produce 4-Methylumbelliferone, which fluoresces on exposure to UV light. Non-coliforms do not produce this enzyme and therefore do not fluoresce on the medium. Escherichia coli is detected by the compound IBDG. The b-glucuronidase produced by Escherichia coli cleaves the substrate to produce a blue indigo color in the colonies. As Escherichia coli is also a total coliform, and also produces b-galactosidase, it will also fluoresce. The antibiotic cefsulodin is added to inhibit the growth of gram-positive bacteria and some non-coliform gram-negative bacteria that can cause false positive reactions.
Orange Serum Media
Organisms known to grow in single strength and concentrated juices are lactic acid and acetic acid bacteria and yeast. Lactobacilli, Leuconostoc and yeast have all been identified as spoilage organisms by numerous authors. Orange serum at pH 5.4 to 5.6 has been reported to yield maximum counts of all types of spoilage organisms in mixed cultures and in single culture comparison tests.
Potato Dextrose Broth and Agar Media
Potato Dextrose Broth is recommended in Standard Methods as the media that gives the most consistent and highest counts for the recoveries of yeast and mold in dairy products. The inclusion of potato extract encourages the growth and development of fungi. Sterile tartaric acid may be added to lower the pH to 3.5 ± 0.2 to further inhibit the growth of conflicting bacteria.
Standard Methods Agar
All bacteria develop on Standard Methods and produce a range of different colored and sized colonies.
Trypticase Soy Broth – Single Strength
General-purpose medium used in qualitative procedures for the cultivation of fastidious and non-fastidious microorganisms. Trypticase Soy Broth – Single Strength complies with the demands of the DIN Norm 10167 for the detection of Escherichia coli serotype 0157:H7 in foods and FDA-BAM for the isolation of enterohemorrhagic Escherichia coli (EHEC). In addition the media conforms to the formula of the U.S. Pharmacopoeia.
Trypticase Soy Broth – Double Strength
TSB broth is a medium that will support the growth of a wide variety of microorganisms including aerobic, facultative and anaerobic bacteria and fungi.