The resistant level of the houseflies to six kinds of insecticides, DDT, Resmethrin, DDVP, Baytex, Sumithion and Diazinon, was examined on the seven strains collected in Malaysia. It was found that their susceptibility is rather higher than that of the Takatsuki strain which is a standard strain in Japan. However, their susceptibility to Sumithion was the same or slightly lower than that of the Takatsuki strain. The resistant level to five of six kinds of insecticides was the highest in the strain of Cameron Highland. The values were close to Singh's data in 1973, and this means that the resistance of the houseflies to the insecticides is increasing in Malaysia.
Repeated experimental reinfection of two subjects indicates that Helicobacter pylori infection does not promote an immune response protective against future reinfection. Our results highlight the importance of preventing reinfection after eradication, through public health initiatives, and possibly treatment of family members. They indicate difficulties for vaccine development, especially therapeutic vaccines.