BACKGROUND:Spread of antibiotic resistance in hospitals is a well-known problem, but studies investigating the importance of factors potentially related to the spread of resistant bacteria in outpatients are sparse. METHODS:Stool samples were obtained from 206 healthy couples in a community setting in Southern Germany in 2002-2003. E. coli was cultured and minimal inhibition concentrations were tested. Prevalences of E. coli resistance to commonly prescribed antibiotics according to potential risk factors were ascertained. RESULTS:Prevalences of ampicillin resistance were 15.7% and 19.4% for women and men, respectively. About ten percent and 15% of all isolates were resistant to cotrimoxazole and doxycycline, respectively. A partner carrying resistance was the main risk factor for being colonized with resistant E. coli. Odds ratios (95% CI) for ampicillin and cotrimoxazole resistance given carriage of resistant isolates by the partner were 6.9 (3.1-15.5) and 3.3 (1.5-18.0), respectively. CONCLUSION:Our data suggest that conjugal transmission may be more important for the spread of antibiotic resistance in the community setting than commonly suspected risk factors such as previous antibiotic intake or hospital contacts.