Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis




Pharmaceutical Sciences

First Advisor

Dr. David S. Burgess


Background: Infections caused by carbapenem-resistant Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae are among the most urgent threats of the infectious disease realm. The incidence of these infections has only been increasing over the years and due to very limited treatment options, mortality is estimated at about 50%.

Methods: To evaluate the in vitro activity of meropenem and polymyxin B against carbapenem-resistant Enterobacteriaceae, antimicrobial susceptibility testing and time-kill studies were performed on K. pneumoniae clinical isolates representing a wide range of meropenem resistance (MICs 4 – 128 mg/L).

Results: Regrowth was observed at clinically relevant concentrations of meropenem alone (4, 16, and 64 mg/L) or polymyxin B alone (0.25 and 1 mg/L) within 24 hours. However, meropenem and polymyxin B in combination were consistently bactericidal, achieving synergistic activity in strains with lower meropenem resistance (MICs ≤32 mg/L).

Conclusions: Our findings are in agreement with the limited available literature, but we add that the synergistic interaction between meropenem and polymyxin B is dependent on the degree of meropenem resistance in KPC-producing K. pneumoniae. This data suggests that lower level resistance to carbapenems may be amenable to antimicrobial combinations involving a carbapenem and a polymyxin.

Digital Object Identifier (DOI)