WATER-BORNE BACTERIA AND SHAMPOO SPOILAGE 287 number, will increase with an increase in batch size. However, during this phase the longer a product is stored prior to packing the greater will be its bacterial population and the greater the proportion of packs containing contaminants. So products should be packed as soon as possible to reduce the frequency of pack contamination. If storage prior to packaging is un- avoidable, viable counts should be performed to establish the advisability of packaging. The inability of total viable counting techniques to detect less than about 30 bacteria per gram of product might be considered to be an argument for their replacement by other more sensitive techniques, e.g. inoculation of a liquid nutrient medium with a sample of product or filtration methods. How- ever, unless the complete absence of contaminants or the absence of specific types of organisms is required these methods will be of doubtful value since a manufacturer will not reject a batch of product, until it has been shown that the contaminants present are capable of multiplying to an unacceptable level. Growth in liquid media has other disadvantages: chance contamina- tion may give rise to false positive results, no information concerning the numbers of bacteria in the product is provided, bacteria capable of growth in the product may be outgrown by those of no significance from a product contamination viewpoint and a standard of sterility is imposed on the product. Experimental inoculation of shampoos with bacteria derived from mains- water indicates that the bacteria capable of growth represent only a small proportion of the total population carried by water (our experience is of course with water from a single source). Using Probability Tables (26) by extrapolation, our results suggest that the number of bacteria capable of multiplying in our model shampoo system is approximately 5 in 100 litres (less than 0.000055/0 of the total number of bacteria present). However, a 2000 kg batch of our model shampoo would contain 1228 1 of water or 60 bacteria capable of surviving and multiplying in this product. This is, according to our results, a sufficient number to contaminate it. Had we used more inhibitory detergent systems (e.g. monoethanolamine lauryl sulphate) or had we used test bacteria less well adapted to growth in sodium lauryl ether sulphate, it is probable that we would have found that more than 50 bacteria were necessary to contaminate our model shampoo. Similarly the frequency of occurrence in water of bacteria capable of sur- vival and multiplication in a product will be least when that product provides an inhospitable environment for bacteria. But when selecting water treat- ment devices or designing plant cleaning and disinfection procedures it is

288 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS necessary to consider extreme conditions, i.e. the product most likely to support bacterial growth. Our results indicate that for certain products a very small number of bacteria only is necessary to contaminate a large batch of product. (Received: 20th March 1974) REFERENCES (1) Wedderburn, D. L. Advan. Pharm. Sci. 1 195 (1964). (2) Savin, J. A. Pharm. J. ii 285 (1967). (3) Morse, L. J., Williams, H. P., Green, R. P. Jr, Eldridge, E. E. and Rotta, J. R. N. Engl. J. Med. 277 472 (1967). (4) Bruch, C. W. Amer. Perfum. Cosmet. 86 45 (1971). (5) Dunnigan, A. P. and Evans, J. R. T. G. A. Cosmet. J. 2 1 39 (1970). (6) Tennenbaum, S. J. Soc. Cosmet. Chem. 18 797 (1967). (7) Bryce, D. M. and Smart, R. J. Soc. Cosmet. Chem. 16 187 (1965). (8) Collins, V. G. Proc. Soc. Water Treat. Exam. 12 40 (1963). (9) Collins, V. G. J. Appl. Bacteriol. 27 143 (1964). (10) Honeywell, G. E., Rueher, F. M. and Staperr, E. M. Devs. Ind. Microbiol. 3 306 (1961) (11) Chambers, C. W. and Clarke, N. A. Advan. AppL Microbiol. 8 105 (1966). (12) Silvey, J. K. G. and Roach, A. W. J. Am. Water Works Assoc. 56 60 (1964). (13) Geldreich, E. E. and Clark, H. F. J. Milk Food Technol. 28 351 (1965). (14) Leifson, E. Int. Bull. Bacteriol. Nomenclature Taxonomy 12 133 (1962). (15) Thistlethwayte, D. K. B. Amer. Perfum. Cosmet. 81 29 (1966). (16) Sykes, G. and Smart, R. Arner. Perfum. Cosmet. 84 45 (1969). (17) Castell, C. H. and McDermott, L. A. Food Res. 7 244 (1942). (18) Schuster, G. and Modde, H. Seifen Ole Fette Wachse 94 709 (1968). (19) Garvie, E. I. J. Bacteriol. 69 393 (1954). (20) Poynter, S. F. B. and Mead, G. C. J. Appl. Bacteriol. 27 182 (1964). (21) Bowen, L. Amer. Perfum. Cosmet. 85 65 (1970). (22) Burman, N. P. Discussion to Proc. Soc. Water Treat. Exam. 12 40 (1963). (23) Eisman, P. C., Kull, F. C. and Mayer, R. L. J. Amer. Pharm. Ass. Sci. Ed. 38 88 (1948) (24) Stamm, J. M., Engelhard, W. E. and Parsons, J. E. AppL Microbiol. 18 376 (1969). (25) Cowan, S. T. and Steel, K. J. Manual for the Identification of Medical Bacteria (1965) (Cambridge University Press, London). (26) Reports on Public Health and Medical Subjects No. 71. The Bacteriological Examination of Water Supplies (1969) (H.S.M.O., London).