![]() The medium should be isotonically balanced and with a pH of 7.4 to prevent lysis of the red blood cells. For optimal demonstration of haemolysis by beta haemolytic Streptococci, sheep blood should be used. It consists of an enriched nutrient agar base with 5% added blood, usually either horse or sheep blood. BLOOD AGARīlood agar is used as a general purpose isolation medium for clinical specimens and for most moderately fastidious bacteria. Their websites are below:įor media with CM numbers after the name, refer to the Oxoid catalogue. More detail and descriptions can be found in the manuals produced by the major media companies – Oxoid and Becton-Dickinson or BD (BBL/Bacto/Difco). These can include solutions of antibiotics and even in some cases, solutions of glucose, which can caramelize in the autoclave. These solutions must be added aseptically after autoclaving. Some reagents added to media are heat sensitive and cannot be autoclaved. Solutions are heated until dissolved, dispensed into tubes, bottles or flasks depending on end use, and sterilized in the autoclave. Broth media is made up in a similar manner, but does not necessarily need to be boiled as it does not contain agar. The concentration of agar in most solid media is about 1.5% or 15g/l, which results in a firm but not fragile medium with sufficient available water for the growth of bacteria. One 100ml bottle of agar will normally make 6 plates containing 15-18mls each. ![]() Agar media intended for pouring into Petri dishes is usually autoclaved in bottles containing 100ml or 500ml. Once cooled, bulk media can be stored at 18 oC for extended periods. The dry powders are added to the water, boiled to fully dissolve the ingredients (essential if the medium contains agar, which does not dissolve at less than 100 oC), dispensed into suitable containers and then autoclaved. Most media is supplied as dehydrated powders (ready mixed by the manufacturers) which must be mixed with water and sterilized before use. THIOSULPHATE CITRATE BILE SALTS SUCROSE AGAR (TCBS) METHYL RED/VOGES PROSKAUER MEDIUM (MR/VP) ![]() Media On this page: MAKING MEDIA - general instructions MEDIAĬYSTINE LACTOSE ELECTROLYTE DEFICIENT (CLED) ![]()
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