In the past couple of years, about 25 recalls have occurred due to potential Salmonella contamination in extruded pet foods. Although heat extrusion has proven to be a relatively safe process, the issue may be linked to aspects such as the specific food formulation, process temperature, moisture content, water activity and post-process contamination. Specifically, Salmonella is more heat resistant at low a_w.  Heat resistance of Salmonella can also be altered by the presence of specific ingredients, e.g., fats.  Manufacturers should be equally cautious about post-process contamination, e.g., the unintended microbial contamination of powder or liquid coatings applied after extrusion cooking without further heat treatment.