Plasmid Profile Analysis of NDM-1 Positive Isolates from Clinical and Environmental Settings

Abstract

Multidrug resistance Gram negative bacteria are a great threat to public health. Metallo--lactamaese producing bacteria are becoming emerging threat by their increasing resistance to β-lactam antibiotics. The New Delhi metallo-β-lactamases (NDM-1) is a novel type of metallo--lactamase named after the city of origion which remains last choice of drug for the treatment of MDR microbial infection. NDM-1 was identified for the first time in clinical isolates of K. pneumoniae and E. coli from a Swedish patient who had sought medical care in New Delhi, India in 2008. Total of 36 NDM-1 positive isolates (meropenem resistance) in which 5 were environmental and 31 were clinical. Tested strains were E. coli, Pseudomonas spp, K. pneumoniae and Enterobacteriaceae. Plasmid profiling of these isolates shows that all the tested isolates carry plasmid of different sizes and numbers. Plasmid stability of 3 isolates (E. coli, Pseudomonas, Enterobacteriaceae) in antibiotic free media was tested. All plasmids were stable after 15 passages of these strains in antibiotic free media. Pseudomonas spp. and E. coli lost plasmid during 8 and 10 passage respectively. To check the plasmid DNA transferability, we transformed plasmid DNA from Pseudomonas (meropenem resistance) to Pseudomonas (meropenem sensitive) and Pseudomonas ATCC (9027) by calcium chloride transformation method, growth on meropenem containing media plates. showed the successful transformation of the plasmid DNA to the meropenem sensitive.