lab final

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Lab final
updated 4 years ago by afrodee
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microbiology
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1

Chemotherapeutic agents

chemical substances used in the treatment of infectious disease.Act on a number of cellular targets. Mechanisms of action include inhibition of cell-wall synthesis, inhibition of protein synthesis, inhibition of nucleic acid, disruption of the cell membrane and inhibition of folic acid synthesis. drugs can be separated in two categories Antibiotics and Synthetic drugs

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Antibiotics

Synthesized and secreted by some true bacteria, actinomycetes, and fungi. products produced by bacteria and mold.

Some are modified and synthesize

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The kirby-Bauer Antibiotic Sensitivity Test Procedure

Used in the antibiotic studies. Mueller-Hinton is the medium used

A standardized diffusion procedure with filter paper discs on agar. it used to determine the drug susceptibility of microorganisms isolated from infectious processes this method allows the rapid determination of the efficacy of a drug by measuring the diameter of the zone of inhibition that results from diffusion of the agent into the medium surrounding the disc.

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Metabolism

The sum total of all chemical reactions needed to sustain life. Two broad categories are catabolism and anabolism

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Catabolism

involves breaking down a large molecule into smaller molecules or ions.

Ex: glucose breaking down into water and CO2

Energy yielding Ex: hydrolysis= lysis with additional water

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Anabolism

smaller molecules joins together to form larger molecules

energy requiring reactions. Ex: dehydration synthesis( loss of water)

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Enzymes

Determine what chemical reactions will take place in cells

A catalysts: lowers the energy of activation,is that energy needed

to cause a chemical reaction to take place

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SUGAR FERMENTATION AND IMViC MEDIA

Phenol Red

Acid production from the fermentation of sugars causes phenol red to turn yellow

Durham tube: gas produced is trapped in top of Durham

Turbidity: indicates growth

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SUGAR FERMENTATION AND IMViC MEDIA

SIM agar deep

a) Hydrogen sulfide: (H2S) production-black precipitate in agar

b) Indole test: test for production of indole from the breakdown of the amino acid tryptophan by the enzyme tryptophan

c) Motility: diffused growth suggests motility/growth confined along the stab indicates lack of motility

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SUGAR FERMENTATION AND IMViC MEDIA

MRVP

originally designed to distinguish Escherichia coli from Escherichia aerogenes as well as distinguish various other enterobacteria

Methyl red test (pH indicator) is positive at a pH below 4.4

ex: Escherichia coli is positive for the methyl test

Voges-Proskauer test for organisms that don't produce sufficient acids to give a positive methyl red test. These organisms often produce 2,3-butanediol whis is basic. Acetoin, an intermediary metabolite of 2,3 butanediol, is tested for in the Voges-Proskauer test

ex: organisms the test pos for Voges-Proskauer include Enterobacter aerogenes

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SUGAR FERMENTATION AND IMViC MEDIA

Simmons citrate agar slant

used to determine whether an organism can use citrate as its sole carbon source through the actions of the enzyme citrase

Citrate positive organisms produce an alkaline product ( sodium carbonate) that increases the pH of the medium and turns it blue

pH indicator: bromothymol blue-a blue color reaction if positive

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SUGAR FERMENTATION AND IMViC MEDIA

Triple Sugar Iron (TSI)

used to differentiate among the enterobacteria and to distinguish them from other gram neg intestinal bacilli. the medium contains glucose (0.1%) and lactose and sucrose ( each at 1.0%). The pH indicator is phenol red:acid production is indicated when the medium turns yellow. If onlu glucose is fermented with acid production the butt will be yellow and the slant will be red. Hydrogen sulfide production is indicated by black deposits within the medium and gas production is indicated by splitting of the agar or by the agar being pushed upward within the tube.

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PRIMARY ISOLATION MEDIA

Phenylethyl Alcohol Agar

Selective: for gram pos bacteria ( gram negs are inhibited by damage to the outer membrane by the alcohols)

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PRIMARY ISOLATION MEDIA

Mannitol Salt Agar

Selective: for the isolation of staphylococci since the high salt concentration (7.5%) inhibits most other bacteria

Differential: phenol red pH indicator causes medium around colonies that ferment mannitol to turn yellow; medium turns red if organism grows without fermenting mannitol

Staphylococcus aureus ferments mannitol but

Staphylococcus epidermidis does not

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PRIMARY ISOLATION MEDIA

Blood Agar

Enrichment: for many fastidious heterotrophs ( especially for some human pathogens)

Differential: can determine whether a bacterium is hemoltic

Alpha hemolysis: partial destruction of red blood cells (RBSs)/greenish tinge in agar around colonies

Beta hemolysis: complete destruction of red blood cells (RBSs)/complete clearing of color in agar around colonies

Gamma hemolysis: no destruction of red blood cells (RBSs)/no change in appearance of agar around colonies

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PRIMARY ISOLATION MEDIA

MacConkey Agar

Selective: for gram neg bacteria (bile salts and crystal violet inhibit Gram pos bacteria)

Differential: contains neutral red pH indicator; bacteria that ferment lactose form red colonies while non-lactose fermenters appears colorless. Intestinal pathogens tend to be non-fermenters

Escherichia coli is a fermenter but Salmonella species are non-fermenters

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PRIMARY ISOLATION MEDIA

Eosin Methylene Blue Agar (EMB)

Selective: for Gram neg bacteria ( dyes inhibit Gram pos bacteria)

Differential: colonies of Gram neg capable of fermenting lactose appear dark purple or have dark centers with light colored edges; non-lactose fermenters appear colorless.

Escherichia coli appear dark purple with a green metallic sheen

Enterobacter aerogenes forms mucoid, brownish-purple, fish-eye colonies with pink edges

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IMViC

acronym that stands for four different test

I-Indole test

M-Methyl red test

V-Voges-Proskauer test

C-Citrate utilization test

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SIM

S-Sulfide

I-Indole

M-Motility

has a enzyme called tryptohan

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Gram Stain

Gram neg Gram pos

crystal violet- purple all purple

Iodine-purple

Alcohol-colorless

Safranin-pink

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Bacteriostaic

the growth of the organism is inhibited not killed but inhibited

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Bactericidal

the organism is killed