Effect of systematic empiric treatment with imipenem on the bacterial ecology in a burns unit

This study took place over 18 months and was divided into three 6 month periods. During the first and third periods, the bacterial ecology of the unit was reviewed, including the observation of bacteria which were isolated and led us to prescribe general antimicrobial therapy, and record the subsequent antibiograms that became available. During the second 6 month period, any patient developing an infection due (or possibly due) to a “Gram negative” strain received imipenem (as β lactam antimicrobial agent), usually combined with tobramycin. The comparison between bacteria and antibiograms isolated during the first and the third periods did not show any increase in multiple resistant bacteria or imipenem resistant strains, including methicillin resistant Staphylococcus aureus (MRSA). During the third period, in comparison with the first, the number of Pseudomonas aeruginosa and Acinetobacter strains was lower; however, the number of Enterobacter and Klebsiella had increased. There was an increase of overall resistance to ticarcillin, but there was no increase in resistance to the other antimicrobials concerned in the study. Therefore, we concluded that wide use of imipenem did not impair the bacterial ecology of the unit, if used with precautions such as high dose regimen, de-escalation, and both pharmacokinetics and ecology monitoring.