Interaction of insulin with Burkholderia pseudomallei may be caused by a preservative

Aim —To re-examine the previously reported in vitro interaction of insulin with Burkholderia pseudomallei , in the light of a suggestion that the interaction may have resulted from the presence of the preservative m-cresol in commercial preparations. Methods —Broth culture studies of B pseudomallei were performed with and without the addition of m-cresol and various preparations of insulin. Results —Growth of B pseudomallei was inhibited by m-cresol at the concentrations found in pharmaceutical insulin preparations, and by the insulin preparation Humulin R, but not by pure insulin. Conclusions —The results of previous experiments may have been confounded by the presence of the preservative m -cresol.