Quantifying Bacterial Cells and Colonies (M) Flashcards
What is the purpose of quantifying microbial cells and colonies (for microbiologists)?
It will give microbiologists rough estimate of microbial density in a certain medium
What is the importance of quantifying microbial cells and colonies?
This is important since some tests in the clinical lab would require estimation of microbial cells and colonies
What are the 2 manners of reporting of quantified microbial cells and colonies?
1) Quantitative
2) Semi-quantitative
What are the different principles that can be used for counting microbial cells?
1) Petroff-Hausser Counting Chamber
2) Spectrophotometric determination
3) Colony counter
What is the process (or steps) of using Petroff-Hausser counting chamber?
1) Bacterial suspension is placed on slide and seeps under cover slip. Suspension fills shallow space of known volume
- > the bacterial suspension is covered by cover slip
- > slide w/ shallow wells and inscribed grid
2) Bacterial cells in squares of grid are counted
- > double lines outline the area to be counted volume of that area is known (something like 10^-4 mL)
What is the purpose of performing Petroff-Hausser counting chamber?
This test is used to determine the amt of microbial cells per unit volume of a suspension
Where are the cells that should be counted seen via Petroff-Hausser counting chamber?
The cells that are counted are in the square (central large square)
What are the components of spectrophotometric (spectrophotometer) determination of bacterial count?
1) Light source
2) Prism
3) Wavelength selection
4) Detector
What are the components of colony counter?
1) Main ON/OFF switch
2) Lens
3) Digital display
4) Plate holder
5) Sensor pen
What are the interpretations in terms of growth quantification of colonies?
1) Scant growth (+)
2) Light growth (++)
3) Moderate growth (+++)
4) Heavy growth (++++)
