Plasmid profile of ESBL producing Gram-negative bacteria and correlation with susceptibility to β-lactam drugs

Abstract

Background: Members of family Enterobacteriaceae can acquire resistance to extended spectrum beta lactams by a number of mechanisms; most important being the plasmid encoded extended spectrum beta lactamase (ESBL) and AmpC beta lactamase. This study has been designed to look for the presence of plasmids and their correlation with drug resistance. Methods: ESBL production was studied in different gram-negative bacteria and susceptibility testing of ESBL positive isolates was done for various beta lactams, cephalosporins and other commonly used drugs against them. Plasmid DNA isolation of all the ESBL positive strains was done by alkalilysis method. Finally the presence of plasmid was correlated with susceptibility to beta lactam drugs. Results: E. coli, K. pneumoniae, Enterobacter aerogenes and A. anitratus harbored multiple plasmids. One plasmid (M.W greater than 21,226 bp) was unanimously present in all the isolates. Conclusion: There is a strong correlation between the number of plasmids harbored by an isolate and resistance to various drugs tested.

Keywords

• Antibiotic resistance
• beta lactamases
• plasmids