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.