Degree Type

Honors Thesis


College of Arts and Sciences



Degree Name

Honors in the Major

First Advisor

Dr. Terri N. Ellis

Second Advisor

Dr. Cliff Ross


Klebsiella pneumoniae is an opportunistic Gram-negative nonmotile bacteria that causes nosocomial infections. In these bacteria, nutrients as well as antibiotics are able to diffuse through the outer membrane via outer membrane porins, transmembrane protein channels. Loss of outer membrane porins, increased capsule production, and a highly mucoid phenotype are commonly observed among antibiotic resistant isolates of this pathogen. The goal of this study was to investigate changes in outer membrane porin expression and capsular polysaccharide production by K. pneumoniae as it transitions to a β-lactam antibiotic resistant phenotype. Klebsiella pneumoniae strain 43816, which is susceptible to β-lactam antibiotics such as cepthalothin, was exposed to increasing concentrations of cephalothin over a 14-day period. During this period, daily samples of the bacteria were assessed for capsule synthesis, gene expression analysis, and changes in the physical appearance of the culture. At the end of the 14-day exposure, cells had assimilated to survive in 7.5 μg/mL of cephalothin, and had taken on a highly mucoid phenotype. High levels of capsular polysaccharides synthesis were confirmed by the uronic acid assay. Minimum inhibitory concentration assay showed treated cultures had become highly resistant to cephalothin. Two-step RT-qPCR demonstrated that this assimilated bacteria exhibited upregulation of magA, which has been linked to invasive, mucoid forms of Klebsiella infection. Additionally, cultures at the end of the treatment consistently showed downregulation of ompK35 and ompK36 and upregulation of ompK26. These data demonstrate that low-level exposure to cephalothin can induce significant changes in cellular phenotype that may impact both the resistance and virulence profile.

Included in

Biology Commons