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REINFORCED CLOSTRIDIAL AGAR (RCM AGAR)
Code: CM0151
A solid medium for the cultivation and enumeration of anaerobes, especially Clostridium species.
Typical Formula* | gm/litre |
Yeast extract | 3.0 |
`Lab-Lemco’ powder | 10.0 |
Peptone | 10.0 |
Glucose | 5.0 |
Soluble starch | 1.0 |
Sodium chloride | 5.0 |
Sodium acetate | 3.0 |
Cysteine hydrochloride | 0.5 |
Agar | 15.0 |
pH 6.8 ± 0.2 @ 25°C |
* Adjusted as required to meet performance standards
DirectionsSuspend 52.5g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.
DescriptionReinforced Clostridial Agar is a solid version of Oxoid Reinforced Clostridial Medium CM0149, suitable for the cultivation and enumeration of clostridia and other anaerobes, lactobacilli, and many other species of bacteria. Reinforced Clostridial Agar does not differ significantly in performance from the pork-starch-pea agar of Anderson1 for the count of anaerobes. It is employed for the estimation of clostridia in food - see below (also Barnes et al.2 and Angelotti3). Attenborough and Scarr4 employed RCM Agar, in conjunction with Membrane Filters, for the count of Clostridium thermosaccharolyticum in sugar.
Reinforced Clostridial Agar is also frequently employed for the investigation of intestinal flora: Perry et al.5 for investigation of bovine rumen streptococci; Williams Smith & Crabb6 used the Oxoid medium with added sodium chloride or blood for counts on human or animal faeces; Barnes & Goldberg7 employed the Oxoid medium with added chlortetracycline hydrochloride or sodium azide and ethyl violet, for the examination of poultry faeces; the Oxoid medium was also used by Goldberg et al.8 for the examination of poultry faecal samples. Williams Smith9 employed Oxoid Reinforced Clostridial Agar with added blood for the `total’ and Lactobacillus count of human and animal faeces; with added blood and neomycin for determination of Bacteroides, anaerobic Gram-negative cocci, `total’ streptococci, sporeformers, yeasts, and `actino’ types.
Sneath10 used Oxoid RCM Agar and other media for the anaerobic count of micro-organisms from soil samples up to approximately 300 years old. Gregory et al.11 also employed the Oxoid medium for the estimation of anaerobes in moulding hay.
TechniqueBarnes and Ingram12,13described the use of RCM Agar for the total viable count of clostridia employing their black glass rod technique. In this method the diluted sample is added to plugged test tubes containing about 9 ml of RCM Agar held at 48°C. The tubes are quickly rotated to mix the contents, and a sterile black glass rod inserted into each tube before the agar sets. They are then sealed with about 1.5cm of RCM Agar containing 1/20,000 methylene blue. Growth is very rapid in this medium and it is necessary to count the colonies before gas production disrupts the agar. The authors suggest that the tubes should be incubated overnight at 25°C and then at 35°C for several hours. The colonies are clearly visible against the black background.
