A comparison of purging and multiple rectal swabs in the detection of inapparent cholera infections.

The relative effectiveness of daily rectal-swab cultures and cultures of purged stools in detecting inapparent infections of Vibrio cholerae were compared in family contacts of cholera patients. In one study of 187 contacts, a combination of purging by various methods plus 5 daily swabs detected 50 infections. Only 27 (54%) were detected by the purge alone, while 47 (94%) were detected by 5 daily rectal-swab cultures. In a second study of two groups of family contacts, purging on the first day did not appear to influence significantly the number of positive rectal-swab cultures obtained during the 4 subsequent days. The relative inefficiency of purging in detecting the inapparent infections among cholera contacts, as compared with its reported efficacy in the chronic convalescent carrier, probably reflects a basic difference in the pathogenesis and site of infection in these different conditions.