Efficacy of Amikacin and Meropenem on Colistin-Induced Klebsiella pneumoniae Persisters

Colistin-based antibiotic therapies have been recommended for the treatment of multidrug-resistant Klebsiella pneumoniae infections. During colistin treatment, persister cells that tolerate antibiotics may arise. Here we designed an in vitro study to assess the killing activity of colistin, meropenem, and amikacin on colistin-induced K. pneumoniae persisters in comparison with starvation-induced persisters. Colistin-induced persisters were generated under exposure to 10 × minimum inhibitory concentration dose of colistin, whereas starvation-induced persisters were produced by limitation of nutrients. In colistin-induced persisters, amikacin totally inhibited cell growth in 6 hours, whereas 98% of the cell population was inhibited by meropenem, and total eradication with meropenem was observed after 24 hours. Both antibiotics also inhibited metabolic activity >88%. The lack of killing effect under colistin exposure suggested to us that these cells could protect themselves from further colistin stress. There was no significant permeabilization change in the cellular membrane with all antibiotics. There was no killing effect on starvation-induced persister cells with the exposure to all antibiotics. In 6 hours, the metabolic activity of the persisters with meropenem and colistin increased 99% and 40%, respectively, whereas there was no increase with amikacin. The sustained inhibition with amikacin was an important finding for antipersister effect of amikacin. Amikacin had rapid and sustained antipersister activity on colistin-induced persister cells. During the colistin treatment of K. pneumoniae infection, the addition of amikacin to the regimen seems to be an effective approach to prevent a recurrence.