To compare the toxic effect and pulsed field gel electrophoresis (PFGE) of 11 Clostridium sporogenes isolates recovered from whey protein concentrate (WPC) suspected to be contaminated with Clostridium botulinum, powdered infant formula (PIF) made from WPC and PIF not related to WPC collected in New Zealand and China.Methods Broth cultures of all C.sporogenes isolates were centrifuged and filtered. The supernatants were orally administered and intraperitoneally injected to ICR mice, respectively. The clinical manifestations of mice were recorded. All isolates were subjected to PFGE analysis and the PFGE patterns were interpreted.Results Mice receiving intraperitoneal injection of the culture supernatant of all 11 C.sporogenesisolates were dead. The most important poisoning symptoms included irritable, hair arched, shortness of breath followed by sudden death within 10 min. No poisoning and deaths occurred in mice with oral administration of the cultures. PFGE analysis revealed that 7 isolates from China and 3 isolates from New Zealand isolated from WPC and its products share the same PFGE profiles. Different PFGE profile was found in 1 isolate from PIF not related to WPC.Conclusion No difference in toxic effect of the culture supernatant produced by 10 C.sporogenes isolated from WPC and its products which collected in China and New Zealand was observed. The results suggested that WPC contaminated with C.sporogenes detected in both China and New Zealand may be from the same sources, owing to the same PFGE profiles in C.sporogenes from both countries were found.