A study of over 1,000 healthy women with no urinary tract infection symptoms showed nearly 9% carried multi-drug resistant Escherichia coli strains in their guts. Additional findings highlight likely reasons behind the pandemic of resistant E. coli strains. They show the value of checking a patients' carrier-status to predict resistant infections, and the need to re-think the clinical significance of bacteria in the urine without symptoms, because pandemic strains can be highly pathogenic to the urinary system and treatment resistant.