Here are some sites with guidelines for low-bacteria diets:
Leukemia Links: The Neutropenic Diet
Fred Hutchinson Cancer Research Center: Diet Guidelines for Immunosuppressed Patients
Healthtouch: Low Bacteria Diet (the same information is at drugs.com)
Seattle Cancer Care Alliance: Diet Guidelines for General Oncology Patients with Low White Blood Counts]
Ohio State University Medical Center: Low Bacterial Diet (PDF file, size 40K; see Reading PDF files)
There isn't an absolute dividing line between "safe" and "unsafe" foods, so you have to use common sense and decide how strictly you want to avoid potential risks.
When my wife was neutropenic, we didn't eat out and didn't get take-out food. We got in the habit of washing our hands more often, rinsing cans before opening them, making sure food was cooked thoroughly, and following the other guidelines we were given.
Some raw vegetables, like cucumbers, were easy to wash so we had them anytime. Some took work to wash (lettuce, one leaf at a time) so we had them only when we felt like taking the trouble. And we skipped some, like bean sprouts, because there was no way to ensure they were safe enough.
Nothing in life is 100% safe, but it's certainly worthwhile to avoid the most risky food choices. Becoming familiar with what's recommended and what's not recommended is the first step.