The Incidence and Character of Vibrios in British Waters

SUMMARY: Forty-nine strains of vibrio were isolated from 32 of 43 samples of fresh water collected in various parts of England and Wales during the period October 1945 to July 1946. More than one kind of vibrio were found in 14 of the samples. The types of vibrio isolated were heterogeneous in their fermentation reactions. Only three gave a cholera-red reaction. Twenty-five produced haemolysin for goat erythrocytes and all the haemolysins tested were filterable through gradacol mem- branes of 75 mp pore diameter; an antiserum prepared against the haemolysin of one strain neutralized those of the other haemolytic water strains and of an El Tor vibrio. Only one serological group of five strains related in '0' and 'H' antigens was found; a few other strains showed H relationship and one (or two) possessed the Ä3 antigen of Vihio cholerae; otherwise the organisms isolated were serologically heterogeneous with little antigenic similarity, to one another or to known Asiatic vibrio types. Compared with the extensive studies of the organisms of the Vibrio group which have been undertaken in India and the Far East, there is little informa- tion concerning their distribution and characters in western countries where cholera no longer occurs. In Britain, Houston (1913) examined a large number of London water samples, mainly from the Thames, for the presence of 'water microbes culturally resembling vibrios ', but after finding 1885 strains atypical in the cholera-red test and in their behaviour towards gelatin he rejected them without further study . The present investigation was therefore started with the following objects : (1) to determine the incidence of vibrios in open waters in this country; (2) to investigate their biochemical and serological characters; (3) to compare them with the true cholera vibrio and with water vibrios isolated in other parts of the world. Method of isolation Specimens were taken in ordinary unsterilized glass beakers, washed out several times in the water under examination. Each sample (180 ml.) was transferred to a sterile screw-capped bottle containing 20 ml. of an enrichment medium composed of 10 yo peptone and 9 % NaCl in distilled water, with the pH adjusted to 9-2 and buffered with a boric acid solution, a few drops of thymol blue being added as indicator. The samples were usually collected during the afternoon and on returning to the laboratory the bottles were left on the bench at room temperature overnight. They were transferred to the 37" incubator at 10 a.m. the following day for 6 hr., after which a few drops of the surface scum was plated on Aronson agar. The bottles were again left on the bench overnight and a second plating was made the following morning.