Cm Res Q

Garcia, Tiffany Verzil D. BSMT3 1. Why is it necessary to refrigerate the agar plates upside down? •

That is, upon the thorough cooling and solidification, the agar emits vapor and eventually that will condense. Refrigerating the plates upside down prevents the condensation from getting on the agar surface, thus avoiding much contamination.

2. Identify at least five clinical specimens and their appropriate primary plating method. • Urine - streak plate method • Cerebrospinal fluid - streak plate method • Throat swabs - Streak plate method/ MicroStreak. • Fecal specimen - streak plate/pour plate method • Blood - pour plate method 3. Identify the types of culture media and give examples of each. • Selective media are used for the growth of only select microorganisms. o eosin-methylene blue agar (EMB) that contains methylene blue – toxic to Gram-positive bacteria, allowing only the growth of Gram negative bacteria o YM (yeast and mold) which has a low pH, deterring bacterial growth o blood agar (used in strep tests), which contains bouvine heart blood that becomes transparent in the presence of hemolytic Streptococcus •

Differential media or indicator media distinguish one microorganism type from another growing on the same media. o MacConkey (MCK), which is differential for lactose fermentation o mannitol salt agar (MSA), which is differential for mannitol fermentation o X-gal plates, which are differential for lac operon mutants

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Enriched media contain the nutrients required to support the growth of a wide variety of organisms, including some of the more fastidious ones. • Blood agar • Chocolate agar

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Transport Media. These are used for the temporary storage of specimens being transported to the laboratory for cultivation. Such media ideally maintain the viability of all organisms in the specimen without altering their concentration. • Stuart transport medium-a non-nutrient soft agar gel • Venkat-Ramakrishnan(VR) medium for v. cholerae

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A chemically-defined (synthetic) medium (Table 4a and 4b) is one in which the exact chemical composition is known.

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A complex (undefined) medium is one in which the exact chemical constitution of the medium is not known.

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A defined medium is a minimal medium if it provides only the exact nutrients (including any growth factors) needed by the organism for growth.

4. Identify some indicators of a faulty culture media. • Improper used of tools or not sterilized tools are used upon preparation. • Use of unspecified reagents or chemicals unneeded in the preparation. • Improperly or not followed aseptic techniques when preparing media. • Prepared media left open (this may cause air borne contamination). • Improper dispensing of mixture that will lead to contamination. 5. What makes a culture media selective? • Selective media inhibits the growth of certain microbes, providing general information regarding the bacteria that are able to grow on this specialized of agar. Thus, it becomes selective when it only tries to pick and segregate the microorganisms needed to be grown while inhibiting the maturation of the other microorganisms sharing the media.

References: • http://microbiology.suite101.com/article.cfm/selective_bacterial_growth_media#ixzz0Jn SDGZYN&D • http://web.indstate.edu/thcme/micro/differential.htm • Gwendolyn R. W. Burton. Burton’s Microbiology for the Health Sciences, eighth edition.