Prevalence of Shigella enterotoxins 1 and 2 among Shigella strains isolated from patients with traveler's diarrhea.

Shigella spp. are known primarily as a cause of bacillary dysentery. However, in an initial phase, numerous patients exhibit watery diarrhea that may or may not be followed by dysentery. New virulence factors associated with the species of Shigella have recently been described. These are enterotoxins 1 and 2 of Shigella (ShET-1 and ShET-2, respectively). The aim of the present study was to determine the prevalence of ShET-1 and ShET-2 in species of Shigella isolated from patients with traveler's diarrhea. During the period from 1993 to 1998, stool samples from 500 travelers with diarrhea were cultured for the isolation of Shigella spp. and other enteropathogens. The detection of ShET-1 and ShET-2 was performed by a PCR technique with specific primers. Among a total of 51 strains of Shigella isolated during this period (22 S. flexneri, 26 S. sonnei, and 3 S. dysenteriae strains), at least one enterotoxin was detected in 31 (60.78%) strains; 2 (9.09%; both of which were S. flexneri strains) produced only ShET-1, while 21 (41.17%; 3 S. flexneri, 15 S. sonnei, and 3 S. dysenteriae strains) produced ShET-2. Furthermore, 8 (15.69%) of 22 S. flexneri strains presented both enterotoxins. Our results show that the prevalence of ShET-2 was high in all the Shigella species studied and confirm that ShET-1 is detected only in S. flexneri.