A bacterial susceptibility test to 31 antibiotics was conducted on the 80 isolated Escherichia coli from the leachates of the landfills in two different operations: semi-aerobic (SL) and anaerobic (AL) landfills. The average population of E. coli from SL and AL leachates were 2.2 x 10(4) and 9.4 x 10(3) CFU/100 ml, respectively. Between 80.8% and 87.5% of the E. coli isolated from both leachates as resistant to the tested antibiotics and high resistances were found to doxycycline (53.8-68.8%), cephalothin (57.5-61.3%), tetracycline (51.3-67.5%) and minocycline (37.5-46.3%). The percentages of isolates resistant to most antibiotics were higher in the AL leachate. The exception was nitrofurantoin to which the isolates from the SL were highly resistant. E. coli from both sources showed similarly high susceptibilities (90-100%) to aminoglycosides, quinolones, chloramphenicol, sulfonamide and some new beta-lactams. The difference in available oxygen in landfills could affect E. coil susceptibility to antibiotics in leachates. (C) 2012 Elsevier Ltd. All rights reserved.