MUELLER HINTON-OXACILLIN-SODIUM CHLORIDE AGAR

Technical Data #1336a / 98.07.08

Mueller Hinton-Oxacillin-Sodium Chloride is used for the detection of oxacillin-resistant Staphylococcus aureus. Salt increased stimulate production and realease of beta-lactamase.


FORMULA
in grams per liter purified filtered water

Beef Extract

2,0

Acid Casein Hydrolysate

17,5

Starch

1,5

Sodium Chloride

40,0

Agar

17,0

Antibiotic

Oxacillin

0,006

 

pH 7,3 +/- 0,1 à 25º C

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


PRECAUTIONS
This medium is for IN VITRO diagnostic use only.


STORAGE
Store prepared media at 2-8º C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-25º C.


SIGN OF DETERIORATION
Media should not be used if the expiry date has passed. Prepared media should not be used if there are signs of contamination or deterioration (shrinking, cracking, evaporation or discoloration). Do not use dehydrated media if it is caked.


DIRECTIONS
Suspend 38 g of Mueller Hinton dehydrated media and 40 g of Sodium Chloride in 1000 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Sterilize at 121º C for 15 minutes. Cool to 45-50º C. Aseptically add 0,006 g of sterile Oxacillin. Mix gently and dispense into sterile Petri dishes. Prepared culture plates may be used immediately or stored in plastic bags at 2-8º C up to six weeks before use.


PROCEDURE
Prior to inoculate, the prepared media should be brought to room temperature.

  1. Into a Mueller Hinton Broth with 4-5 similar colonies from an overnight growth, prepare a suspension and adjust to 0,5 Mc Farland Standard.
  2. Dip a sterile cotton swab into the suspension, express the excess fluid and inoculate plates as a «spot» or strake a quadrant of the plate.
  3. Incubate at 35º C for a full 24 hours.


QUALITY CONTROL

Results after 24 hrs at 35ºC

Organisms

ATCC

Growth

Staphylococcus aureus

29213

-

Staphylococcus aureus

33862

-

Methicillin-Resistant S. aureus (MRSA)

43300

+

Methicillin-Resistant S. aureus (MRSA)

clinical strain

+


LIMITATIONS OF METHOD
This medium is only a part of the identification. Other tests may be required. Methicillin/Oxacillin Resistance in coagulase-negative staphylococci is must reliably detected after 48 hours incubation.


REFERENCES

  1. Baker, C.N., C. Thornsberry, R.W. Hawkinson. 1983 Inoculum standardization in antimicrobial susceptibility testing: evaluation of overnight agar cultures and the rapid inoculum standardization system. 17:450-457.
  2. Hindler, J.A., C.B. Inderlied. 1985 Effect of the source of Mueller-Hinton Agar and resistance frequency on the detection of Methicillin-Resistant Staphylococcus aureus. J. Clin. Microbiol. 21:205-210.
  3. Mc Dougal, L.K., C. Thornsberry. 1984 New recommendations for disk diffusion antimicrobial susceptibility tests for Methicillin-Resistant (heteroresistant) Staphylococci. J. Clin. Microbiol. 19:482-488.
  4. Mc Dougal, L.K., C. Thornsberry. 1986. The role of b-lactamase in staphylococcal resistance to penicillinase-resistant Penicillins and Cephalosporins. 23:832-839.
  5. Thornsberry, C., L.K. Mc Dougal. 1983 Successful use of broth microdilution in susceptibility tests for methicillin-resistant (heteroresistant) Staphylococci. 18:1084-1091.
  6. NCCLS. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically - 4th edition. Approved standard. NCCLS Document M7-A4, Vol.17, No 2.
  7. NCCLS. Performance standards for antimicrobial disk susceptibility tests - 4th edition. Approved standard. NCCLS Document M2-A4, Vol 10, No 7.


CATALOGUE NUMBERS

Dehydrated media

 

 

Mueller Hinton

500 g

QB-39-3206

Sodium Chloride

500 g

QB-39-4109

 

 

 

Prepared media

 

 

Plates, 100x15 mm

10/pkg

1336

 

 

 

Mueller Hinton Broth

 

 

Tubes 16x125 mm

10/pkg

2663


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