Initially the CDC thought it might be able to trace the infections to a single source — one breeder or commercial breeding facility where the bacterium had spread. But as the investigators learned more about the byzantine world of the breeding and distribution of dogs sold in pet stores, it became clear there wasn’t a single source.

In effect, the system was creating the problem. “These dogs were coming from a large variety of sources,” Laughlin said.

Price wasn’t impressed. “If your system requires a constant or regular dose of antibiotics to keep the animals healthy, your system’s broken. You’ve designed a system that makes sick animals,” he said.