Flashcards
COLONIAL MORPHOLOGY & BASIC BIOCHEMICAL TESTS
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- 1LABORATORY CULTUREculture media : nutrient solutions used to grow microbes in the laboratory
- Liquid or solid : chemically defined, complex, differential, selective - 2CULTURE MEDIA - PURPOSEto prepare sterile, nutritive media which supports the growth of bacterial cultures
- 3CULTURE MEDIA - PRINCIPLE- requires ingredients which supports basic growth of bacterial colonies
- must also be sterile so as not to grow environmental contaminants - 4CULTURE MEDIA - BASIC GROWTH MEDIA FOR BACTERIA IS- Nutrient broth/nutrient agar
- preparations may be made in various forms : broths, deep, slant, or plates - 5PREPARATION OF MEDIAIf media is poured too hot, condensation will form inside the plate. The condensation will interfere with growing isolated colonies
- 6DIFFERENT PREPARATIONS OF MEDIA1. nutrient agar slant
2. nutrient agar broth
3. nutrient agar deep - 7ASEPTIC TECHNIQUE - PURPOSETransfer of microbes from one medium to another sterile medium without contamination of the culture, sterile medium or the surroundings
- 8ASEPTIC TECHNIQUE - PRINCIPLE- gather all necessary materials (bacterial culture, growth media, bunsen burner, transfer tools)
- label tubes properly
- check each organism to be transferred using stock cultures
- discard contaminated materials properly - 9ISOLATED COLONIESthey are streaked at the end of streak
- 10STREAK PLATE - PURPOSEused to obtaining isolated colonies from a mix of cultures
- 11STREAK PLATE - PRINCIPLE- essentially a method t dilute the numebr of organisms
- allows for individual colonies to be isolated from other colonies - 12COLONIAL MORPHOLOGY - purpose- To identify isolated bacterial colonies based upon appearance
- permits selection and transfer of different species from a mixed culture
- allows transfer of single colony for cultivation of pure culture - 13COLONIAL MORPHOLOGY : TERMS1. colony shape and size
2. edge characteristic s
3. elevation
4. colour
5. texture - 141. colony shape and sizeround, irregular, punctiform (tiny)
- 152. margin (edge characteristics)entire (smooth)
undulate (wavy)
lobate (lobed) - 163. Elevationconvex, umbonate, flat, raised
- 174. COLOURcolour or pigment
opaque or transparent
shiny or dull - 185. TEXTUREmoist, mucoid or dry or rough
- 19TYPES OF AGAR FOR ISOLATION AND IDENTIFICATION- Selective agar
- Differential agar - 20SELECTIVE AGAR- some species will grow but not others
- selectively inhibits some bacteria - 21DIFFERENTIAL AGAR- different species will look different on the agar
- indicators eg dyes - colour changes - 22BLOOD AGARblood agar is used both as an enriched medium for growing fastidious bacteria and as a differential medium
- exotoxins called haemolysins cause lysis of the red blood cells in the media
- the type of haemolysis is a useful tool for identification of many gram +ve cocci - 23HAEMOLYSIS PATTERNS - BETA HAEMOLYSIScomplete lysis of the RBCs and haemoglobin, results in complete clearing around colonies
- 24HAEMOLYSIS PATTERNS - ALPHA HAEMOLYSIS= partial lysis of RBC's and haemoglobin ; produces a greenish discolouration of the blood agar around colonies
- 25HAEMOLYSIS PATTERNS - GAMMAno haemolysis = no change in medium
- 26DIFFERENTIAL MEDIA- Mant differential agars contain pH indicators in combination with carbohydrates
- If the carbohydrate is used by the organism = ph changes and the colour of the medium surrounding colonies change - 27MANNITOL SALT AGAR (MSA) - PURPOSEMSA is a both selective and differential growth medium ; used to differentiate pathogenic staphylococcus species
- 28MSA - PRINCIPLE- MSA can determine two characteristics of bacteria :
1. whether it can tolerate salt
2. whether it can ferment mannitol
The medium contains an indicator, phenol red
1. ph 7.0 red
2. p.h 7.4 and above = deep red
3. p.h 6.8 and below = yellow - 29MSA - SALT TOLERANCEmedium contains 7.5% salt therefore it selects organisms that can tolerate salt = selective medium
- 30MSA - FERMENTATION OF MANNITOLorganism can either ferment mannitol or not
1. if fermentation does not occur = medium remains red
2. if fermentation occurs = medium changes colour to yellow because of the acidic by products
therefore it is a differential test as well - 31MacConkey AGARis selective and differential
- 32Selective Macconkey AGARgram -ve will grow
gram +ve will not = due to addition of bile salts and crystal violet - 33DIFFERENTIAL MACCONKEY AGARlactose fermenters appear pink
non lactose appear colourless - 34CETRIMIDE AGAR- selective medium for pseudomonas aeruginosa
produce coloured and fluorescent iron chelators
- inhibits other bacteria - 35PRIMARY TESTS : CATALASE- adding hydrogen peroxide to culture sample which catalyses it back into water and oxygen
- gas and bubble = +ve test - 36PRIMARY TESTS : OXIDASE-enzyme cyt C = transfer electrons to oxygen
-oxidised reagent = colour changes = +ve test - 37OXIDATION/FERMENTATION REACTIONto determine whether an organism uses oxidative fermentative metabolism of carbohydrates
- 38OXIDATION/FERMENTATION REACTION- uses carb either by oxidative or fermentative pathway
-aerobic or anaerobic - 39METHOD OF OXIDATION/FERMENTATION REACTION1. inoculate two tubes of OF medium for each organism
2. inoculation is carried out as a stab to within 1cm at the bottom of tube
3. overlay one tube only with sterile parafrin oil to exclude oxygen
4. paraffin overlay suggests anaerobic organisms
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- Flashcards on COLONIAL MORPHOLOGY & BASIC BIOCHEMICAL TESTS, created by Simmy Braich on 15/06/2014.
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