The evolution of multidrug resistance in Klebsiella species in response to selective pressure and the extent to which this may be reversible is not yet fully understood. Since carbapenem-resistant Enterobacteriaceae (CRE) is considered a public health threat by the World Health Organization (WHO) and the Centers for Disease Control and prevention (CDC), more studies need to be done to understand the evolution of antibiotic resistance mechanisms to determine if it is possible to reverse this trend.
K. quasipneumoniae FK688 is a clinical isolate that has been shown to be resistant to multiple antibiotics including imipenem. In this strain, the ompk36 gene has a mutation resulting in a non-functional porin. The loss of functional porins has been shown to be a frequently occurring mechanism by which bacterial cells can develop multidrug resistance. Since genome sequencing indicated that ompK36 in FK688 was mutated, and potentially responsible for the increased resistance to imipenem, it is an interesting model to study the evolution process.
To study the evolution of imipenem resistance in FK688, ompK36 in this strain was reverted to the wildtype “ompK+” genotype, where porin functionality was recovered and imipenem susceptibility was restored.
The aim of this study is to compare the engineered imipenem-susceptible FK688 “ompK+” to the drug-resistant “ompK-” progenitor FK688 strain using a competitive fitness assay and a drug gradient method. With these two methods the evolution of the antibiotic resistance and fitness cost of the mutation at different time points will be monitored. Subsequently, whole genome sequence data will be used to evaluate the rate and occurrence of genetic changes and how the “ompK+” strain evolves in the presence of antibiotic selection pressure.