Escherichia coli Infections (E coli) By Larry M Bush, MD, FACP, Charles E Schmidt College of Medicine, Florida Atlantic University; Maria T Vazquez-Pertejo, MD, FACP, Wellington Regional Medical Center Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Diagnosis Treatment The gram-negative bacterium Escherichia coli is the most numerous aerobic commensal inhabitant of the large intestine.