Abstract
Bacteriological studies with carbenicillin and gentamicin individually and with the combination of these antibiotics suggest their effect to be additive in action and often synergistic. Of sixty-five organisms tested in vitro, the majority Gram-negative, forty-seven were resistant to ampicillin, thirty-seven to carbenicillin, twenty-four to gentamicin and only six to carbenicillin plus gentamicin. Out of sixty-seven patients undergoing major abdominal surgery, thirty were randomly allocated to receive carbenicillin plus gentamicin post-operatively and of these one developed an infection. The other thirty-seven patients received either ampicillin or no antibiotic and nine developed infections. The combined antibiotic regime seems suitable for prophylaxis for patients undergoing major abdominal surgery with a high risk of infection.