Dry cat food is not pathogen-free. Fungal mycotoxins, produced by molds, are common grain contaminants. A 2009 study on mycotxins noted that commercial pet foods - particularly dry food - are very frequently contaminated with mycotoxins. (See this link for details: http://bit.ly/186WSDm )
Unrefrigerated dry foods often sit on store shelves, in warehouses, and cabinets for many weeks or months before they're consumed.