Had UTI due to e coli, responded well to macro bid. Less than week later, after having pelvic exam and sex, have UTI due to staph sapro (50,000 cfu/ml). Finishing bactrim 7 days. Am 14 weeks pregnant. Otherwise, excellent health. Questions: what could have caused the staph infection? Do I need to be vigilant about regular urine tests to make sure doesn't come back? Why isn't bactrim indicated when pregnant?