Experts question samples used in superbug claims
The criteria adopted by the UK-Australia group of scientists to determine the presence of the superbug gene, New Delhi metallo-ß-lactamase 1, in drinking water samples of the national capital is “unscientific and violates the established norms of research,” argue scientists.
The team from the UK and Australia collected 50 samples of tap water from Delhi Jal Board and compared them with 70 samples of sewage effluent of Cardiff city in the UK. The team declared that while two of the 50 Delhi samples had the super bug gene, NDM-1, none of the samples from Cardiff had the gene in them.
“Fair scientific investigation demands that the samples are identical. If you are doing a comparative study, the parameters selected should be the same. For instance, if you want to compare height, you should take only height into consideration. You cannot compare the height of one individual with the weight of another. Similarly, in this case too, the samples should be either potable water or sewage water,” senior geneticist Dr M.N. Khaja said.
According to Dr Niyaz Ahmed, group leader, Pathogen BiologyLaboratory, University of Hyderabad, the UK study was based on “convenience sampling”. “When conveniently spotted and potentially suspected sources are picked up as first choice and tested with highly sensitive tools such as PCR and real time PCR, it is possible to get positivity even for places such as Switzerland. However, culture or PCR positivity does not mean that a potential epidemic is brewing,” he added. “The general practice is to select similar and identical samples of the material to be studied. If the UK-Australia team wanted to prove that their sewage water is better than our drinking water, they should have first conducted studies on potable water drawn from New Delhi and Cardiff. After ruling out the presence of the superbug protein in the potable water of Cardiff, they should have gone for the sewage effluent tests to further prove their point. But, they have not ruled out the presence of the gene in the potable water of Cardiff,” a senior CCMB scientist, who does not want to be quoted, told this correspondent. Scientists argue that this particular bacteria may not survive under harsh atmosphere, though bacterial species by nature are known to live in difficult environments.
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