Sampling Procedure 3458

3.1.1. Equipment Surfaces

1. Open the sterile swab (see Note 3), grasp the end of a stick, not touching any portion that might be inserted into the vial, and remove the swab aseptically (see Note 4).

2. Open a buffered rinse solution, and moisten the swab head (pressing out the excess solution against the interior wall of the vial with a rotating motion).

3. Make a 30° angle contact with the surface. Rub the swab head slowly and thoroughly over 50 cm2 of surface three times, reversing direction between successive strokes. Move the swab on a path 2 cm wide by 25 cm long or other dimensions to cover an equivalent area.

4. Return the swab head to the solution. Rinse briefly in the solution and press out the excess (see Note 5).

3.1.2. Unmeasured Surface Areas

Pump impellers, gaskets, rings, valve seats, filler nozzles, and so on, have been swabbed, the results are reported on the basis of the entire sampling site instead of a measured area.

3.1.3. Utensils To Be Examined

1. At least glasses, cups, and spoons (3,5) should be examined. Four of each should be selected at random from where clean utensils are stored. If a direct check of dishwashing efficacy is desired, utensils should be selected from those recently washed.

2. Use one swab for each four or more similar utensils.

3. The significant surfaces of utensils consist of the upper 1.5 cm of the inner and outer rims of cups and glasses and the entire inner and outer surfaces of the bowls and spoons.

3.1.4. Forks and Surfaces of Dishes

The area to be swabbed should include the entire inner and outer surfaces of the tines of forks and the inner surfaces of plates and blows.

After the fifth area has been swabbed, position the swab head in the vial, and break or cut it with sterile scissors or another device (2), leaving the swab head in the vial. Replace the screw cap, put the vial in a waterproof container packed in cracked ice or other suitable refrigerant, deliver to the laboratory, and analyze within 24 h.

3.2. Plating Swab Rinse Solutions

1. Remove the vial from refrigerated storage.

2. Shake, making 50 complete cycles of 15 cm in 10 s.

3. Plate 1.0- and 0.1-mL portions of rinse solution (with appropriate media, depending on the organisms of interest).

4. Incubate plates, count colonies, and calculate the number of colonies recovered from 50 cm2 (equivalent to 1 mL of rinse).

5. For utensils, report the count as the residual bacterial count per utensil examined.

3.3. Calculation

1. Swab three utensils.

3. Results are of 150 colonies.

4. Count per utensil is 175.

5. For satisfactory results in adequately cleaned and sanitized food service equipment on which five areas of 50 cm2 have been swabbed, residual bacterial count should not exceed 500.

4. Notes

1. The swabs made of calcium alginate are soluble in aqueous solutions containing 1% of sodium hexametaphosphate, sodium glycerophosphate, sodium citrate, or any mixture of these.

2. Rayon and dacron swabs may also be used.

3. The swabs may be sterilized in the laboratory.

4. Swab four more 50-cm2 areas of the surface being sampled, rinsing the swab in the solution after each swabbing (removing the excess).

5. Care should be taken to prevent contamination by handling during sampling.

References

1. Buchbinder, L. T. C., Buck, R. Jr., Phelps, P. M., Stone, R. V., and Tiedman, W. D. (1947) Investigation of the swab rinse technic for examination eating and drinking utensils. Am. J. Public Health 37, 373-378.

2. Buck, T. C. Jr. and Kaplan, E. (1944) A sterile cutting device for swab vial outfits utilizing wood applicators. J. Milk Technol. 7, 141-142.

3. American Public Health Association (1978) Standard Methods for the Examination of Dairy Products, 14th ed. (Marth, E. H. ed.). Washington DC, American Public Health Association.

4. American Public Health Association (1984) Compendium of Methods for the Microbiological Examination of Foods, 2nd ed. (Speck, M. L. ed.). Compiled by the APHA Technical Commitee on Microbiological Methods for Foods. Washington DC, American Public Health Association.

5. Code of Federal Regulations (1983) Title 21, Food and Drugs. Par 129, Processing and Bottling of Bottled Drinking Water. Washington, DC, US Govt. Printing Office.

6. Tiedman, W. D., chairman (1984) Technic for the bacteriological examination of food utensils. Committee report. Am. J. Public Health Yearbook 1947-48. Part 2, pp. 68-70.

7. US Department of Health, Education, and Welfare. Public Health Service (1967) Procedure for the Bacteriological Examination of Food Utensils and/or Food Equipment Surfaces. Public Health Service Publication No. 1631, Technical Information Bulletin No. 1. Washington, DC, Food and Drug Administration,

8. Walter, W. G. and Potter, J. (1963) Bacteriological field studies on eating utensils and fat surfaces. J. Environ. Health 26, 187-197.

Agar Contact Method Replicate Organism Direct Agar Contact (rodac)

1. Introduction

The RODAC plate method is a simple and valuable technique for estimating the sanitary quality or surfaces in food factories and ideally should be used on previously cleaned and sanitized surfaces (1,2). This method is indicated when quantitative date are sought from flat, impervious surfaces (It should not be used for irregular, pervious, or creviced surfaces) (3). Colony counts can be made only on plates with 200 or fewer colonies (4).

2. Materials

1. Plastic RODAC plates with 15.5-16.5 mL of the specific media. Plate count agar is used for total counts, and differential medium may be used if qualitative values are sought (see Note 1).

2. When carried out on surfaces previously subjected to chemical microbicide treatment, added neutralizers are needed for the media (5,6): 0.5% polysorbate, which neutralizes some substituted phenolic disinfectants, and Tween-80 plus 0.07% soy lecithin, which neutralizes quaternary ammonium compounds.

3. Methods

1. Remove the plastic cover and carefully press the agar surface to the surface being sampled. Make certain that the entire agar meniscus contacts the surface, using a rolling uniform pressure on the back of the plate to effect contact (see Note 1).

2. Replace the cover and incubate in an inverted position for 24-48 h. A 24-h incubation period when heavy contamination is present and 48 h when contamination is light should be allowed (see Note 2).

3. Colonies should be recorded as the number of colonies per RODAC plate or number of colonies per cm2.

4. Notes

1. The meniscus of the agar should rise above the rim of the plate to give a slightly convex surface. This is very important so the agar makes proper contact with the surface to be sampled.

2. Following preparation of the plates, incubate at 32°C for 18-24 h as a sterility check.

They should be used within the succeeding 12 h unless they are wrapped and refrigerated.

References

1. American Public Health Association (1978) Standard Methods for the Examination of Dairy Products, 14th ed. (Marth, E. H., ed.). Washington DC, American Public Health Association.

2. American Public Health Association (1984) Compendium of Methods for the Microbiological Examination of Foods, 2nd ed. (Speck, M. L., ed.). Compiled by the APHA Technical Commitee on Microbiological Methods for Foods. Washington DC, American Public Health Association.

3. Angeloti, R. J., Wilson, L., Litsky, W., and Walter, W. G. (1964) Comparative evaluation of the cotton swab and RODAC methods for the recovery of Bacillus subtilis spore contamination from stainless steel surfaces. Health Lab. Sci. 1, 289-296.

4. Code of Federal Regulations (1983) Title 21, Food and Drugs. Par 129, Processing and Bottling of Bottled Drinking Water. Washington, DC, US Govt. Printing Office.

5. Engley., F. B. and Dey., B. P. (1970) A universal neutralizing medium for antimicrobial chemicals. Chemical Specialities Manufacturer's Association, Proceedings of the 56th Meeting, New York.

6. Weber, G. R. and Black, L. A. 1948. Inhibitors for neutralizing the germicidal action of quaternary ammonium compounds. Soap Sanitary Chem. 24, 137-142.

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