Analysis of S. dysenteriae type 1 and S. flexneri strains isolated from environmental waters in Bangladesh for the presence of ipaH genes. Genomic DNAs were digested with HindIII, and corresponding Southern blots were hybridized with the ipaH probe. Identities of the environmental isolates (strain numbers) represented in different lanes are as follows. Lanes 1 and 9 represent clinical strains of S. dysenteriae 1 (SD-16) and S. flexneri (SF-12163), respectively, that were included in the study for comparison with environmental isolates. Lanes 2 through 5 represent S. dysenteriae 1 isolates (SD-461, SD-462, SD-469, and SD-479), and lanes 6 through 8 represent S. flexneri isolates (SF-455, SF-505, and SF-507). Numbers indicating molecular sizes of bands correspond to the 1-kb DNA ladder (Gibco BRL) used as molecular size markers.