Widespread occurrence of specific restriction endonucleases in Salmonella infantis, Salmonella thompson, and Salmonella blockley isolated from humans in Japan.

Specific restriction endonucleases were detected in three serotypes of Salmonella spp. isolated from humans in Japan from 1970 to 1987: an isoschizomer of AvaII endonuclease at a frequency of 0.91 in Salmonella infantis, an isoschizomer of KpnI at a frequency of 0.34 in Salmonella thompson, and an isoschizomer of StyI at a frequency of 0.30 in Salmonella blockley. Of interest is that restriction endonuclease-producing S. thompson was detected at high frequencies in the 1970s but at low frequencies in the 1980s.