2) Goetz, A., Tsuneishi, N.: Application of molecular filter membranes to the bacteriological analysis of water, J. Am. Water Works Assn., 43 (12): 943-969,1951. 3) Clark, H.F. et al.: The membrane filter in sanitary bacteriology, Pub. Health Reports, 66: 951-977, 1951. 4) Kabler, P.W., Clark, H. F.: The use of differential media with the membrane filter, Am. J. Pub. Health, 42: 390-392, 1952. 6) Abbott, J. D., Shannon, R.: A method for typing Shigella sonnei using colicine production as a marker, J. Clin. Path., 11 : 71-77, 1958. 7) Gillies, R. R.: Colicine production as an epidemiological marker of Shigella sonnei, J. Hyg. Camb., 62 (1): 1-9, 1964. Application of Membrane Filter Method for Isolation of Causative Shigella from Drinking Water in Waterborne Dysentery Outbreaks Hiroshi ZEN-YOJI, Senzo SAKAI, Yasuo KUDOH, Takeshi ITOH, Kura SAITOH and Tsutomu MARUYAMA Department of Bacteriology, Tokyo-to Laboratories for Medical Sciences, Shinjuku-Ku, Tokyo It is generally thought to be extremely difficult to isolate and identify causative Shigella from drinking water in the course of dysentery epidemics.

Despite the fact that there were not a few cases of dysentery outbreaks in this country in the last several decades in which waterborne infection was suspected as its cause, well legitimated reports of success in isolating the causative organisms from the imputable drinking water were scarce. To our knowledge, the first successful case was reported by Meguro et al. including the authors in 1966 in which the causative Shigella was isolated from the well water by the use of Membrane Filter Method (MF) in a dysentery outbreak occurring in Higashi Murayama city, Tokyo, in that year. Since then, such successful cases with MF have been accumulated by the authors and the number of them reached eight by May, 1969. This paper describes the details of the experiments with MF comparing with some other ordinary methods and its clinical application to eight waterborne-suspected dysentery outbreaks. 1) Experimentally, excellent results were obtained with MF, compared with ordinary methods such as enrichment broth culture method and centrifuged sediment culture method. MF could recover the Shigella from the Shigella-suspended physiological saline so diluted as 3-5 bacillus per 500 ml fluid, whereas enrichment broth culture and centrifuged sediment culture required 30-50 and 300-500 bacillus per 500 ml saline for the isolation, respectively. 2) Clinical applications of MF to eight waterborne-suspected dysentery outbreaks occurring within Tokyo Metropolis during 1966-1969 were all successful. Shsgella sonnei were isolated in 6 of them, and Shigella flexneri 2a and 3a in the other two cases, respectively. 3) In all instances, the isolates from the drinking water were examined for the serotype, colicine type and antibiotic sensitivity patterns, and compared with those of the isolates from the patients. They were found identical, then consequently, the causality of the isolates from the drinking water was confirmed in all these eight incidences.