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The pour plate technique is the typical technique used to prepare plate count agars. Here, the inoculum is added to the molten agar before pouring the plate. The molten agar is cooled to about 45 degrees Celsius and is poured using a sterile method into a petri dish containing a specific diluted sample.
The plates are left upright on the bench to dry before inversion and incubation at 37 °C for 18 – 24 hours (or appropriate incubation conditions considering the organism and agar used). Each sector is observed for growth, high concentrations will give a confluent growth over the area of the drop, or a large number of small/merged colonies.
The laboratory procedure involves making serial dilutions of the sample (1:10, 1:100, 1:1000, etc.) in sterile water and cultivating these on nutrient agar in a dish that is sealed and incubated. Typical media include plate count agar for a general count or MacConkey agar to count Gram-negative bacteria such as E. coli. Typically one set of ...
The traditional colony count method could be modified to measure antimicrobial activity in the 96-well plate without the need for sampling the wells and spreading surviving cells on agar plates by simply adding an equal volume of twice-concentrated broth after the two hour incubation in the low salt buffer.
A third technique is using sterile glass beads to plate out cells. In this technique, cells are grown in a liquid culture, in which a small volume is pipetted on the agar plate and then spread out with the beads. Replica plating is another technique used to plate out cells on agar plates. These four techniques are the most common, but others ...
The spread plate method wherein the sample (in a small volume) is spread across the surface of a nutrient agar plate and allowed to dry before incubation for counting. [11] The membrane filter method wherein the sample is filtered through a membrane filter, then the filter placed on the surface of a nutrient agar plate.
A bacterial reference chart is used to determine the number of bacteria in the sample. Appropriate treatment is applied to the water source once abnormal levels of bacterial activity are noticed. Once water treatment is effective the bacterial count produced by the dip slide test should be low, approximately <10 4. [2]
Agar dilution is one of two methods (along with broth dilution) used by researchers to determine the minimum inhibitory concentration (MIC) of antibiotics. It is the dilution method most frequently used to test the effectiveness of new antibiotics when a few antibiotics are tested against a large panel of different bacteria.