Mc FARLAND STANDARDS

Technical Data #2900a / 2013.08.31

Mc Farland Standards are used for standardization of numbers of bacteria when required by procedures or for susceptibility testing. The basic 0,5 Mc Farland Standard contains approximately 1x107 to 1x108 CFU/ml (1x1010 to 1x1011 CFU/L)

 


 

FORMULA

0,5 Mc Farland Standard

 

Barium Chloride, 0,048M solution

0,5 ml

Sulfuric Acid, 0,18M solution

99,5 ml

O.D at 625 nm

0,08-0,1

1,0 Mc Farland Standard

 

Barium Chloride, 0,048M solution

1,0 ml

Sulfuric Acid, 0,18M solution

99,0 ml

O.D. at 625 nm

0,16-0,2

2,0 Mc Farland Standard

 

Barium Chloride, 0,048M solution

2,0 ml

Sulfuric Acid, 0,18M solution

98,0 ml

O.D. at 625 nm

0,32-0,4

3,0 Mc Farland Standard

 

Barium Chloride, 0,048M solution

3,0 ml

Sulfuric Acid, 0,18M solution

97,0 ml

O.D. at 625 nm

0,48-0,6

4,0 Mc Farland Standard

 

Barium Chloride, 0,048M solution

4,0 ml

Sulfuric Acid, 0,18M solution

96,0 ml

O.D. at 625 nm

0,64-0,8

5,0 Mc Farland Standard

 

Barium Chloride, 0,048M solution

5,0 ml

Sulfuric Acid, 0,18M solution

95,0 ml

O.D. at 625 nm

0,8-1,0

This approximate formula may be adjusted and/or enriched to obtain best results.


PRECAUTIONS
This medium is for laboratory use only.


STORAGE
Store standards at 2-30º C protected from direct light.


SIGN OF DETERIORATION
Standards should not be used three months after production date. Standards should not be used if there are signs of contamination or deterioration (evaporation or discoloration).


PROCEDURE
Vigourously agitate these turbidity standards on vortex just before use.

  1. Inoculate a broth with 4-5 similar colonies from an agar plate culture. Mix thouroughly.
  2. Incubate at 35º C for 2-6 hours until it achieves or exceeds the turbidity of Mc Farland Standard required. If necessary, dilute suspension with broth or saline to obtain a turbidity visually comparable to required standard.
  3. Following standardized procedures inoculate plates for antimicrobial disk susceptibility tests. For testing the nutritive capacity of a medium dilute cell suspension according to previous references.


LIMITATIONS OF METHOD

Replace standards or recheck thier densities three months after production date.


REFERENCES

  1. Lennette, E.H., Ballows, A., Hausler, W.J.Jr., and Shadomy, H.J. Manual of Clinical Microbiology. 4th ed. 1985 Washington D.C.: American society for Microbiology.
  2. NCCLS 1990 Quality assurance for commercially prepared microbiological culture media Approved standard Document M22-A Vol.10, No.14
  3. NCCLS 1990 Performance standards for antimicrobial disk susceptibility tests 4th ed. Approved standard Document M2-A4 Vol.10, No.7


CATALOGUE NUMBERS

0,5 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2901
     
1,0 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2586
     
0,5 and 1,0 Mc Farland Standard:    
Tubes, 16x125 mm (5 tubes of each) 10/pkg 2951
     
2,0 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2921
     
3,0 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2911
     
4,0 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2931
     
5,0 Mc Farland Standard:    
Tubes, 16x125 mm 10/pkg 2950
     
Complete Set, 16x125 mm    
0,5, 1,0, 2,0, 3,0, 5,0 (2 tubes of each) 10/pkg 2900
1,0, 2,0, 3,0, 4,0, 5,0 (2 tubes of each) 10/pkg 2901

 


 

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