32 notecards = 8 pages (4 cards per page)
Selective for Gram Negative bacterium and differential for the fermentation of lactose.
Mannitol Salt Agar
Selective for Halophilic/Osmotolerant organisms (7.5% salt) and differential for fermentation of Mannitol.
Antimicrobial susceptibility of bacteria
How strongly treatments affect bacteria. Susceptible, Intermediate, Resistant
Disc diffusion method
Lawn innoculate an agar plate and place a disc containing antibiotic on it. let the disc sit for a day then measure the zone of inhibition. Compare the diameter (mm) to an interpretive chart
Zone of Inhibition
Full diameter (mm) of agar with no growth - does not include any area that look s hazy. Related to rate of diffusion.
Classification of organism as resistant to a particular antibiotic.
An antibiotic producing no plaque will most likely be ineffective against the bacteria causing your bunny's infection.
Classification of organism as intermediate to a particular antibiotic.
- there are some members of the bacterial population that are sensitive to this particular antibiotic, but others that are genetically immune to its effects.
Classification of organism as susceptible to a particular antibiotic.
The antibiotic has inhibited their growth and/or killed them, meaning that this particular antibiotic should be effective against the infection your rabbit has.
How to test disinfectants effectiveness against a given organism
Disk diffusion tests using MSA, MacConkey's Agar, Mueller Hinton Agar or a simple Nutrient agar with lawn innoculation.
Phenol Red broth: Interpretation and significance
Tests for the fermentation of different sugars (polymers of glucose or mannitol, etc).
Methol Red Test: Interpretation and significance
Tests for mixed acid fermentation.
Voges'-Proskauer Test: Interpretation and significance
Tests for the presence of acid byproducts (in particular ACETOIN) from enteric bacteria in the tube.
Citrate Test: Interpretation and significance
Does the organism being tested utilize citrate for energy? If it does there will be a change in pH - alkaline byproducts will be released cause the agar to turn blue and potentially some growth
Urease Test: Interpretation and significance
If urease is produced it hydrolyzes the urea in the agar to ammonia which raises the pH of the medium and changes it from yellow to red (indicated a positive response).
Litmus milk test
Litmus milk is a complex medium that can potentially distinguish among many species of bacteria. Litmus milk has several components that can be metabolized: lactose (milk sugar); casein (milk protein); and litmus (a pH indicator that is purple to blue at neutral to alkaline pH and pink under acid conditions).
Reactions of the Litmus Milk Medium Test
Acid <-- there are acidic byproducts (pink)
Litmus Milk Medium Test: Acid
lactose is fermented, leaving behind acidic byproducts and turning the medium pink
Litmus Milk Medium Test: Alkaline
lactose is not fermented and proteins are instead used for energy, the solution will become alkaline and more blue.
Litmus Milk Medium Test: Coagulation
Casein (milk protein) may be digested. This will coagulate the milk to form a curd (a solid).
Litmus Milk Medium Test: Reduction
The litmus (pH indicator) may be reduced and become colorless. The culture will then look milk white.
Litmus Milk Medium Test: Peptinization/Digestion
The casein (milk protein) may be metabolized all the way down to individual amino acids. This process, called peptonization, results in a clear (not milky) liquid that is usually brown in color.
Interpretation and significance: Nitrate Reduction Test
- The organism is able to reduces NO3 to N2 gas
Procedure: Nitrate Reduction Test
1. Inoculate nitrate broth with an isolate and incubate for 48 hours.
Interpretation and significance: Starch Hydrolysis Test
Lack of a zone of clearing when Iodine is added to an innoculated (and grown) agar plate means that the microbe was unable to hydrolyze starch and does not produce amalyse
What comprises a SIM test?
Sulfur Reduction Test
Interpretation and significance: Sulfur Reduction test (SIM)
If an organism can reduce sulfur to hydrogen sulfide, the hydrogen sulfide will combine with the iron to form ferric sulfide, which is a black precipitate. If there is any blackening of the medium, it indicates the reduction of sulfur and is a positive result.
Interpretation and significance: Indole Production test (SIM)
Drop Kovac's reagent on the top of the SIM agar. If the puddle turns stays yellow/clear NEGATIVE.
Interpretation and significance: Motility test (SIM)
- View the agar tube to determine motility of the organism. Negative result – the organism will not have deviated from the line of insertion. Positive result – anaerobic response: the organism diffuses through the agar; aerobic response: organism gathers on the top of the agar (forms a film).
Interpretation and significance: Catalase Test
Does the organism catalyze H2O2. A positive result will release O2 gas.
Interpretation and significance: Oxidase Test
- Used to differentiate the bacteria that posses the cytochrome oxidase c enzyme from those who do not. If the organism is aerobic it will be able to reduce oxygen.