Staff Report ISD : Tahir Hussain, a PhD student from the National University of Sciences and Technology, Pakistan in collaboration with scientists of Washington University, USA worked on clinical pathogenic bacteria collected in Pakistani and US hospitals. The exciting research work was published in the journal, “Emerging Infectious Diseases”, which is the top ranked Journal of epidemiology in the world.
The researchers studied a family of bacteria called Enterobacteriaceae, which includes E. coli, Klebsiella pneumoniae and Enterobacter. Some strains of these bacteria do not cause illness and can help keep the body healthy. But in people with weakened immune systems, infections of these bacteria can be deadly, especially if found resistant to carbapenem- the last line antibiotics.
Two genes are primarily responsible for carbapenem-resistant versions of these disease-causing bacteria. One gene, KPC, was detected in New York in 2001 and quickly spread around most of the world, with the exception of India, Pakistan and other South Asian countries.
A second carbapenem resistance gene, NDM-1, was identified in 2008 in New Delhi, India. It was soon detected throughout South Asia, and most patients in other countries infected by bacteria with NDM-1 have had an epidemiological link to South Asian countries.
Tahir Hussain along with other researchers in the laboratory of Dr. Gautam Dantas, at Washington University compared the whole genomes of carbapenem-resistant bacteria isolated in the United States with those of carbapenem-resistant bacteria isolated in Pakistan.
Based on the apparent geographic exclusivity of the two resistance genes, the scientists expected to find that bacteria from the two regions were genetically different. Such differences could explain why the two resistance genes weren't intermingling. But the researchers' results showed otherwise. The bacteria's high genetic similarity suggests that the antibiotic resistance genes could be shared easily between bacteria from the two geographic regions.
The researchers also sequenced a special portion of bacterial genetic material called plasmids. Most of a bacteria's DNA is found in its chromosome, but bacteria also have many extra, smaller and circular bits of DNA known as plasmids that easily can pass from one bacterial strain to another. A plasmid is like a bacterial gene delivery truck; it is the primary way antibiotic resistance genes spread between bacteria.
The researchers identified a few key instances in which the plasmids carrying NDM-1 or KPC were nearly identical, meaning they easily could facilitate the spread of antibiotic resistance between disease-causing bacteria found in the United States and South Asia.
Commenting on these very important research findings, Dr. Gautam Dantas, associate professor of pathology and immunology at Washington University, said “Carbapenems are one of our last resorts for treating bacterial infections, what we use when nothing else works. Given what we know now, I don't think it's overstating the case to say that for certain types of infections, we may be looking at the start of the post-antibiotic era, a time when most of the antibiotics we rely on to treat bacterial infections are no longer effective”
The research was reported by Washington University School of Medicine, and appeared online in Emerging Infectious Diseases.
Mitchell W. Pesesky*, Tahir Hussain*, Meghan Wallace, Bin Wang, Saadia Andleeb, Carey-Ann D. Burnham, Gautam Dantas. KPC and NDM-1 Genes in Related Enterobacteriaceae Strains and Plasmids from Pakistan and the United States. Emerging Infectious Diseases, 2015; 21 (6)
Mitchell W. Pesesky and Tahir Hussain contributed equally to this work.
The paper can be accessed at DOI: 10.3201/eid2106.141504
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