Adaptation of the membrane filter technique to the recovery of Vibrio comma from water samples.

The use of the membrane filter in bacteriological water analysis was initiated by Goetz and Tsuneishi (J. Am. Water Works Assoc., 43, 943, 1951). It is being applied principally for the detection of Escherichia coli. Kabler and Clark (Am. J. Public Health, 42, 390, 1952) found this method useful also for the recovery of Salmonella typhosa from water but there has been no report on the utilization of the membrane filter in the diagnosis of Vibrio comma. Since the culture of V. comma from water samples in standard media is often difficult, the possibility of the employment of membrane filters for such examinations was investigated. Artificially contaminated water samples with various pH values were used in the experiments. One strain each of Inaba and Ogawa types in concentrations of either 1 to 10 or 50 to 100 each per 100 ml water sample served as test organisms. E. coli and Aerobacter aerogenes, 101 to 106 cells per 100-ml of water, were added in the second series of the tests. "Millipore" ifiter (MF) disks were used in conjunction with pyrex millipore filter holders. The holders were sterilized in boiling water for 2 min between operations. After the filtration of 100-ml samples of artificially contaminated water, the filter disks were put on the surface of modified Aronson plates in individual petri dishes. This medium consisted of beef extract, 0.3 per cent; pancreatic digest of casein (Difco), 1.5 per cent; agar, 1 per cent; sucrose and dextrin, 1 per cent each; sodium carbonate, 0.5 per cent; basic fuchsin, 0.012 per cent; and sodium sulfite, 0.2 per cent. The disks were observed under the dissecting microscope and with the naked eye after incubation for 6 and 24 hr. All tests were carried out in duplicate. As controls, 100-ml portions of 2 per cent pancreatic digest of casein and 1 per cent sodium chloride, adjusted to pH 8.4, were added to 100-ml aliquots of the artificially contaminated water samples, and the solution readjusted to pH 8.4 if indicated. After incubation for 8 hr two Aronson plates were streaked with one loopful of the growth from each peptone broth bottle. The Aronson medium was identical with