therapeutic use of leeches (hyrudotherapy) has increased, and it has been shown that they can transmit bacteria associated with infections in 20% of patients. two species of leeches have been found in antioquia, colombia, apparently promising for such therapy. this study was done to identify bacteria in the surface, mouth and intestine of these species and to test the antibiotic sensitivity of the isolates. the studied species were haementeria sp., and oxytychus ornatus. specimens were obtained from their surface, mouth and intestine. blood agar, blood agar with ampicillin, and eosine-methylene blue agar were used as culture media. identification and sensitivity tests were carried out with the vitek (biomerieux？) automated method. a total of 26 isolates was obtained belonging to 12 species and nine genera. isolates were sensitive to the commonly used antibiotics. we suggest to do antibiotic prophylaxis in patients undergoing hyrudotherapy, and to implement standardized protocols to disinfect the animals before use and for the cleaning of the aquarium where they are kept.