The PFGE information on Sam’s isolate is now available. The PFGE pattern matches an isolate from an ill person in Kentucky and another from South Carolina; both of the patients report recent exposure to rodents. This PFGE pattern was uncommon, representing 23 of 17,737 isolates in the S. Typhimurium database. These three human cases might represent a common source outbreak.
You still do not know if the isolate from Melvin (the mouse) is related to the isolate from Sam (the child). The antibiotic resistance pattern is the same, but you do not know yet if there is a PFGE match between Sam and Melvin’s Salmonella isolates.
Even more interestingly, the CDC PulseNet search finds a matching PFGE pattern from a Salmonella outbreak that occurred this last month in another state. You call the state health department in this state and are surprised to learn that the outbreak was among workers at a pet store. Furthermore, some of the pet rodents at the pet store had been sick and specimens from sick rodents had yielded Salmonella Typhimurium with the same antibiotic resistance pattern and PFGE pattern as the workers and as the isolate from Sam. Now you’re getting somewhere!
You call the public health veterinarian who investigated the outbreak at the pet store and who submitted the specimens from the rodents. The veterinarian tells you that the pet store obtained the rodents from a large distributor who had experienced a major die off of rodents after receiving a shipment of 780 mice from Iowa. Diarrhea was present in the majority of ill mice. Distribution of the animals to pet stores was halted, but not before 243 of the original 780 mice had been sent to various pet stores where they were sold to the public. Of the remaining mice, 60% had died by the end of the month and the rest were humanely euthanized.