Background: Escherichia coli (E. coli) bacteria normally live in the intestines of healthy people and animals. Most varieties of E. coli are harmless or cause relatively brief diarrhea.

Aim: To find the relationship between dose, and duration of laser beam with diarrhea patients.

Methods: E. coli species were taken from stool patients, and then it was cultured and incubated for 24 hours in Petri dishes, and coulter them in 24 tube of nutrition agar. 4 groups A, B, C, and D, from each Petri dish we take a culture and growth in nitric broth and then irradiated for different the same time (15 minutes) and for different number of times.

Results: Group A was considered as control, the intensity of laser beam was changed from 1.310 to 1.522 while the number of the bacterial species were decreased from 400, 300, 200, 100, 60, and 90 to groups A, B, C, D, E, and F respectively. Conclusions: the irradiation of these species with laser decrease the bacterial strain activity and this affected with respect to duration times, and with respects to time interval between each irradiation.

Keywords: E. coli species, diarrhea treatment, low level laser, irradiation