The story of a superbug: NDM-1 may revert back to normal bacterium
By Syed Akbar
Here is what Dr Niyaz Ahmed, Professor of bacterial genomics, University of Hyderabad, says:
NDM-1 is said to be circulating in drinking water in New Delhi. Does the super bug survive in open water bodies? What are its implications for public health? Survival and stability in water and soil, of pathogenic bacteria and in particular those equipped with the plasmid encoded NDM-1 character, is a tricky issue, mainly dependent on the parameters such as temperature, organic matter, suspended toxic substances, metal ions and the level of contamination (bacterial inoculum or dosage). Moreover, bacterial pathogenic behaviour is not per cent guaranteed when it is free living (outside the host body) due to the dynamic evolutionary events taking place to ensure adaptation. Mobilisation and sharing of drug resistance encoding apparatuses among different species of bacteria is again not as straightforward as it is assumed. Environment has a great deal of regulatory role in this case. Also, resistance phenotypes are not permanent and the mutants could revert back and become sensitive. It all depends on the evolutionary dynamics of bacteria that are dictated by the environment and the host immune status. Can the gene in this bacterium triggers mutations in other bacteria leading them to new super bugs? Theoretically yes, practically no. It is not straightforward. Genetic transformation experiments which are carefully controlled in the laboratories could perhaps document such events but this phenomenon under natural conditions is difficult to occur and could be a chance event. Genetic exchange in the environment is hindered by the presence of nearly a dozen mechanistic barriers and the composition of the environment such as different organic compounds, chemicals, salts and metal ions etc. which circumvent the success of horizontal gene transfer. Despite these, if the plasmids transfer to a heterologous host bacterium, their survival in the new niche is not always guaranteed. Such rare exchanges could at the most be of ecological significance but might not be of health significance for sure. Again, there are numerous spatial and temporal events that govern the link between the ecological reservoirs and human exposures. What's the implication - health and economics - on India? I think the situation demands an improvement in our community hygiene technology and infrastructure, although, the present campaign of the British microbiologists and their pharma sponsors is entirely directed at denting the medical and health services industry in India. Who is going to gain? I am sure the packaged drinking water industry (mineral water) is going to gain a lot out of this issue!