How can we ascertain if smelly heel lesions are from bacterial or fungus nature ?

Culture: To distinguish a culture is necessary. A faster test for fungus is a koh. The fungus can be seen under the microscope. A dilute clorox bath will help decrease bacteria.

Lab diagnosis: At the office or in the clinic, we can get biopsy or aspiration samples from these heel lesions and send them to microbiology lab for culture (specify in order for both bacterial and fungal cultures), gram stain, pas stain & koh. The lab report would tell u what growths they find, whether bacterial (aerobic/ anaerobic) or fungus, with the name of the specific bugs or fungi.