Minimum Inhibitory Concentration, Minimum Bactericidal Concentration, Plaque Forming Units, Colony Forming Units, McFarland Standard

1. Applied Microbiology
MIC, MBC, CFU, PFU, McFarland
ZAG

2. Some Terms Related to Antibiotics
 MIC : Minimum Inhibitory Concentration
 This is the lowest concentration of an antimicrobial drug
that prevents visible growth of a microorganism after
overnight incubation with media.
 MBC : Minimum Bactericidal Concentration
 The minimum bactericidal concentration is the lowest
concentration of an antibacterial agent required to kill a
particular bacterium.

3. McFarland unit
 McFarland Standards are used to standardize the
approximate number of bacteria in a liquid suspension by
comparing the turbidity of the test suspension with that of
the McFarland Standard.
 A McFarland Standard is a chemical solution of barium chloride
and sulfuric acid; the reaction between these two chemicals
results in the production of a fine precipitate, barium sulfate. When
shaken well, the turbidity of a McFarland Standard is visually
comparable to a bacterial suspension of known concentration.

4. McFarland Turbidity Standard
 There are different McFarland units, according to the
concentration of Cell density (Number of bacterial
cells).
 1.5x 10^8 colony forming units (CFU/ml) are present
in 0.5 McFarland Units.
 These are also Commercially available.

5. CFU : Colony Forming Units
 colony-forming unit (CFU or cfu) is a measure of
viable bacterial or fungal cells.
 CFU measures only viable cells.
 results are given as CFU/mL (colony-forming units per
milliliter) for liquids, and CFU/g (colony-forming units per
gram) for solids.
 CFU can be calculated using miles and misra method.

6. Plaque Forming Units
 In virology, a plaque-forming unit (PFU) is a
measure of the number of particles capable
of forming plaques per unit volume, such as virus
particles.

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