A week ago today my son severely bruised a kidney while playing baseball. He had quite a lot of blood in his urine for 3+ days. His last urinalysis was Tuesday and they said the bleeding had stopped. Today we get a call that he has e. coli and needs to start on Bactrim. How serious is e.coli? Is this because of the trauma to the kidney? How effective is the Bactrim? I'm concerned because he suffered from osteomylitis about 10 months ago and was barraged with antibiotics (including vancomycin by IV for a month) and since then he has had two ear infections, a trachial infection, a sinus infection, and now this. He has always been healthy prior to the osteomylitis. He eats well, takes vitamins and is very active in baseball. He's almost 20 yrs. old. I appreciate any information. Thanks.