COUNTING AND TESTING FOR MICRO-ORGANISMS 75 for the microbial control of pharmaceutical and cosmetic preparations or raw materials. These include total counts and microbial limit tests for specific harmful organisms such as coliforms or E. coli, Salmonellae, Pseudomonas spp. and Staphylococcus aureus (37, 40, 43, 45). Bruch (47) has suggested other organisms which should be excluded from topical products and has ranked them in importance to the areas of body applica- tion. The organisms suggested are those mentioned previously, excluding Salmonellae, and with the addition of all other pseudomonads, Klebsiella and S. marcescens. Btihlmann (25) has also provided methods for Entero- bacteriaceae, enterococcus, Clostridium perfringens and Bacillus cereus. Others will no doubt follow in time. With the introduction of these requirements much effort will be required from microbiologists and their staff. Numerous total counts will be required and these are time-consuming. Simpler and more rapid methods are required and according to Olsen (49) automation seems to offer the greatest possibility. Three methods are under active consideration. Firstly, an auto- mated aerobic plate count is under development at the F.D.A. The principle is that the sample is deposited on the plate at a decreasing rate in the form of an Archimedes spiral pattern. Since the amount of sample and the rate of deposit are both known, the number of bacteria in the original sample can be calculated from the number of colonies along any line segment. Estimates of bacterial concentration can also be made by comparison with a standard set of plates. Secondly, a method for estimating the number of colonies on a plate is being developed and is based on counting electronic- ally using a miniature photoelectric cell scanner and counter. Thirdly, the fluorescent antibody method for the detection of Salmonellae is receiving attention and is described by Fantasia (48). The complex problem of sampling for test purposes has not been dis- cussed. It is still a subject of much debate in conventional sterility testing. For non-sterile products the problem is enormous. CONCLUSION Microbial standards can have little meaning unless they are based on effective methods for the detection and enumeration of undesirable organ- isms to be excluded. An inadequate method that gives false or misleading results can mean rejection of a good product or sale and use of a con- taminated product. The former is costly and wasteful and the latter is a danger to public health. There is still insufficient comparative data available

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