Molecular Characterization and Susceptibility Testing of Extended Spectrum Β-Lactamase (Esbl) Producing Enterobacteriaceae

Abstract

In 2014 alone, 266.1 million courses of antibiotics were dispensed to outpatients by U.S. pharmacies, of which over 30% were later deemed unnecessary (CDC, 2014). The heightened use of antibiotics in medicine has led to the development of antibiotic resistance in pathogenic Enterobacteriaceae, such as Gram-negative Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae). One of the most useful antibiotics utilized to treat and cure infections are the b-lactam class of antimicrobial agents. Overexposure of E. coli and K. pneumoniae to blactams has stimulated dynamic, unprecedented evolution of blactamases, expanding their activity against all b-lactam antibiotics (Pitout & Laupland, 2008; Paterson & Bonomo, 2005). The goal of the present study was to investigate the phenotypic and genotypic properties of 62 ESBL presumptive enterobacteriaceae retained in the Micromyx (Kalamazoo, MI) repository. Phenotypic testing was conducted by broth microdilution Minimum Inhibitory Concentration testing (MIC) testing, and genotypic testing was conducted by the method of Polymerase Chain Reaction (PCR) and gel electrophoresis. Further MIC testing was conducted using sixteen antibiotics commonly used by hospitals in the United States to combat these bacterial pathogens. The Extended Spectrum b-Lactamase (ESBL) producing pathogens’ ability to infect and damage its host is largely unknown, therefore we hypothesized that E. coli and K. pneumoniae strains harboring multiple combinations of ESBLs would relate to higher resistances of these commonly used antibiotics.