Description
Intended Use and Principle of Procedure |
Sabouraud Dextrose Agar conforms with the specifications of The United States Pharmacopeia (USP). Sabouraud Dextrose Agar is used in qualitative procedures for the cultivation of pathogenic and nonpathogenic fungi, particularly dermatophytes. The medium is rendered more selective for fungi Fluid Sabouraud Medium is used for cultivating yeasts, molds, and aciduric microorganisms and detecting yeasts and molds in normally sterile materials. Sabouraud dextrose media are peptone media supplemented with dextrose to support the growth of fungi. Media are also provided with maltose substituted for the dextrose. Peptones are sources of nitrogenous growth factors. Carbohydrates provide an energy source for the growth of microorganisms. Gentamicin is an aminoglycoside antibiotic that inhibits the growth of gram-negative bacteria. Chloramphenicol is inhibitory to a wide range of gram-negative and gram-positive bacteria, and cycloheximide is an antifungal agent that is primarily active against saprophytic fungi and does not inhibit yeasts or dermatophytes. Lecithin neutralizes quaternary ammonium compounds, and polysorbate 80 neutralizes substituted phenolic disinfectants. For the Sterile Pack products, the entire double-bagged product is subjected to a sterilizing dose of gamma radiation. Thus, the contents inside the outer bag are sterile. This allows the inner bag to be aseptically removed and brought into an environment- a mentally controlled area without introducing contaminants. A third sterile bag is included as a transport device. Since the agar medium has been sterilized after packaging, the presence of microbial growth after sampling and incubation can be relied upon to represent the presence of environmental contami- nants and not pre-existing microorganisms in the medium that may have been introduced during manufacture. The RODAC plates have a marked grid to facilitate counting organisms. The Sterile Pack Finger Dab Isolator plates are triple-bagged and are intended for sampling gloved hands. |
Summary and Explanation |
Sabouraud Dextrose Agar is a general-purpose medium that Sabouraud devised for the cultivation of dermatophytes.1 The low pH of approximately 5.6 is favorable for the growth of fungi, especially dermatophytes, and slightly inhibitory to contaminating bacteria in clinical specimens.2-4 This medium is recommended in the USP for use in performing total combined mold and yeast counts (Microbial Limit Tests). The addition of antimicrobics is a modification designed to increase bacterial inhibition. RODAC (Replicate Organism Detection and Counting) environmental sampling plates are specially constructed so that an agar medium can be over-filled, producing a meniscus or dome-shaped surface that can be pressed onto a surface for sampling its microbial burden. These plates are used in a variety of programs to establish and monitor cleaning techniques and schedules.6-10 After touching the surface to be sampled with the medium, the environmental sampling dish is covered and incubated at an appropriate temperature. The presence and number of microorganisms are determined by the appearance of colonies on the surface of the agar medium.11 Collection of samples from the same area before and after cleaning and treatment with a disinfectant permits the evaluation of the efficacy of sanitary procedures. Sabouraud Maltose Agar is a modification of Sabouraud Dextrose Agar with maltose substituted for the dextrose. It is a selective medium due to the acid pH. Davidson et al. reported that Sabouraud Maltose Agar was a satisfactory medium in their studies of infections caused by Microsporum audouini, M. lanosum, and Trichophyton gypseum. Davidson and Dowding also used this medium to isolate T. gypseum from a case of tinea barbae. Sabouraud Maltose Broth is a modification of Sabouraud Dextrose Broth in which maltose is substituted for dextrose. It is selective due to its acid pH and is used for the detection of fungi. Fluid Sabouraud Medium is employed in sterility test procedures to determine the presence of molds, yeasts, and aciduric microorganisms. The acid reaction of the final medium is inhibitive to a large number of bacteria and makes the medium particularly well-suited for cultivating fungi and acidophilic microorganisms. |
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