Isolation of Hemagglutinative Non-el Tor Cholera Vibrios.

During 1963, El Tor cholera spread through Thailand and Burma, and finally appeared in the Chittagong area of East Pakistan in November (Yen et al., East Pakistan MIed. J. 8:22, 1964). With disease caused by the El Tor vibrio within 80 km of areas under study by this laboratory, all vibrio isolates which agglutinated in cholera antisera were screened by the chicken erythrocyte agglutination test proposed by Finkelstein and AIukerjee (Proc. Soc. Exp. Biol. M1ed. 112:355, 1963) to differentiate El Tor from classic cholera vibrios. On 10 January 1964, rectal swabs were received in alkaline tellurite bile peptone broth from six individuals with presumed cholera. These swabs had been obtained by a government health visitor on 6 January from a village adjacent to the vaccine study area of this laboratory. From all swabs, Vibrio cholerae Inaba (V. comma) was isolated; agar-surface growth of two of these cultures agglutinated chicken cells in the Finkelstein and MIukerjee slide agglutination test. During the ensuing 6 weeks, O group I agglutinable vibrios were isolated from 384 other individuals. From six individuals, hemagglutinative vibrios were obtained; in three of these, a nonhemagglutinative vibrio was isolated at the same time as the hemagglutinative one. No hemagglutinative strains had been found among the V. cholerae cultures isolated from 750 individuals previously studied. UTntil 13 September 1964, V. cholerae cultures were isolated from an additional 160 individuals (17 Ogawa and 143 Inaba), but none was hemagglutinative, despite a special search for such vibrios. Sixty-six typical Ogawa serotype El Tor vibrio strains received during this latter period from various other laboratories were all hemagglutinative. Because typical El Tor vibrios had been isolated in East Pakistan in November 1963. the eight hemagglutinative strains were believed to herald the appearance of El Tor cholera within our study area. Accordingly, these strains, together with the nonhemagglutinative strains Vol. 89, No. 3 Printed in U.S.A.