State of the Planet

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Microbial Drug Resistance: Interview with Kartik Chandran, Part 1


Kartik Chandran is an Assistant Professor at the Columbia University Department of Earth and Environmental Engineering and the Director of CUBES (Columbia Earth Institute/UNESCO Joint Programme on Biosphere and Society). He is also a leader in the field of providing clean and healthy water.  In addition to research, fieldwork, teaching and speaking engagements, he is co-organizing the first New York City Water Summit. Professor Chandran took time to speak to Julia Apland Hitz of the Columbia Water Center about his work and its significance within the Climate Change context.

Part One of the interview will cover the issue of Biological Resistance, while Part Two will address Nitrogen in Wastewater Treatment and practical applications of research.

You are trying to reduce drug resistant bacteria and drug resistant genes in wastewater treatment plants. What does bacterial resistance mean for the general public?

If you are simply to look at a drinking water treatment plant, development of resistance to compounds like chlorine, by bacteria – pathogenic or non-pathogenic – basically means we have to dump a lot more chlorine into our drinking water to disinfect it. That’s one straight impact.

Furthermore, down the line if there’s an exchange of genetic elements coding for resistance from non-pathogenic to pathogenic bacteria, there’s a significant impact because now we have pathogens that are harmful to all sorts of other hosts, but they are also resistant to any strategies that are employed against them.

I think (bacterial resistance) is already ranked in the top five in terms of impending human health threats. There are major drug manufacturing companies always trying to come up with drugs that are more and more potent. This has already been going on for a long time, so this is a cat and mouse game that the pharmaceutical companies play with the microorganisms.

How does microbial resistance affect ecosystems?

It directly impacts the diversity, the microbic ecology, as we know it. Essentially, there is enrichment or selection of communities which are resistant to one or more factors, or different factors, so in that sense the microbal ecology has changed quite significantly.

As you know, microbes contribute to global elemental cycling. There will always be a link between the structural makeup of a community and what they catalyze in terms of reaction. So there could be very, very far-ranging impacts all the way to the global elemental cycle.

And of course, if you leave aside human beings, there are also other organisms that bacteria interact with at all different trophic levels, and conceivably that could all change. Higher level organisms have developed mechanisms to combat bacterial infection, a viral infection, for example. Now if there are bacteria which are more resistant to these immune responses, then it’s going to lead to changes in other levels of ecology as well.

How are we actually contributing to the problem?

One of the direct ways that we are contributing is by discharging our unused medicines, antibiotics and so on and so forth, needlessly using anti- microbic compounds, at suboptimal doses or nonoptimal doses. That’s one direct way.

The other way we are directly contributing to drug resistance is by polluting the environment, not with the drugs themselves, but with all sorts of other compounds. For example, there is a very strong link between metal pollution and resistance to antibiotics. So the more metals we discharge, the more the organisms are exposed to these metals. Some of them always find a way to cope with the metal concentrations. In many cases, metal resistance and drug resistance are coded on the same genetic element, and so it is very likely that they are co-expressed.

How does climate change itself contribute to this problem?

This is actually a very interesting area of research. We know that climate change has resulted in very unpredictable precipitation – more severe in some cases, or in some cases extended periods of drought, wider temperature fluctuations. One of the thoughts is that these extreme events essentially act as a trigger. Organisms are eventually able to cope with these extreme events – extreme in the sense of nutrient loading due to resistance – so there could be prolonged lack of nutrients, in some cases starvation, followed by periods of other eutrophic conditions, or feast. The feast/famine also gives rise to all sorts of non-specific stress responses in bacteria.

And a lot of these non-specific stress responses can also include pathogenicity and drug resistance. Climate change, in a sense, can contribute to increased pathogenicity and drug resistance. But there are givens for and against, so this is an active area of research.

Part 2 .

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