Raw sewage flows in a steady stream into Bellandur lake, bringing with it heavy metals, froth-inducing phosphorus, coliforms and other microorganisms. The murky waters of the cesspool may even be a breeding ground for bacteria to develop into stronger, more drug-resistant varieties.
When Mahesha J., who was doing his masters thesis in Ashoka Trust for Research in Ecology and the Environment (ATREE), and researcher Priyanka Jamwal from Centre for Environment and Development at ATREE compared bacterial samples from ‘relatively-cleaner’ Jakkur with that of Bellandur lake, the results were stark.
Bacteria isolated from the severely polluted Bellandur lake had developed resistance to more antibiotics than those at Jakkur lake where an STP and a wetland provide layers of purification.
In a comparison of 10 bacterial species with 10 common antibiotics, researchers found that in Jakkur lake, bacteria had developed resistance in 37 cases; that is, each bacteria species developed resistance to between one and six antibiotic drugs. However, in Bellandur, this number goes up to 51.
“Bacteria have almost universally developed resistance to drugs such as amoxcillin and cefoperazone, which is seen in the figures for Jakkur and Bellandur. But it is the variation of the other drugs that is a concern,” said Mr. Mahesha.
Take for instance, Citrobacter species, which can cause a wide spectrum of infections from urinary tract to the respiratory tract, has resistance to six drugs in Jakkur lake. At Bellandur, it has resistance to eight drugs. Klebsiella, which can cause pneumonia, has seen resistance to seven drugs in Bellandur, compared to five in Jakkur.
“The results were surprising. I repeated the experiment and found the same results... I can only guess that the chemicals in Bellandur lake were expediting mutation of these bacteria, allowing them to develop resistance to drugs which are present in the lake,” said Mr. Mahesha.
The research first took root with identifying common antibiotics present in significant quantities. In 2017, Ms. Jamwal and researchers from Portsmouth in the UK deployed Chemcatcher, a novel technology that can find out medical compounds present in water and their concentrations.
Their tests in Jakkur lake, Vrishabhavathi valley and sewage flowing out of two apartment complexes showed the presence of antibiotics, antidepressants, antifungals, antihistamines, anti-inflammatory, epilepsy, beta-blockers and painkillers in the water.
This provided a base to narrow down on 10 common antibiotics, all of which are Beta Lactam antibiotics that are widely used. They tested the bacterial samples against these drugs.
After the isolation of each sample, the bacterial colony’s resistance was tested by measuring the ‘zone of inhibition’ around discs that were dipped in antibiotic compound. If the area around the disc was clear, it meant that the bacteria was still sensitive to the drug, while if the disc had no effect, it implied that the bacteria was resistant. A lower concentration of bacterial species around the species showed ‘intermediate’ resistance, where the drug merely inhibits growth of bacteria but may not be killing it completely.
Overall, the 10 ‘Jakkur’ bacterial species had 26 intermediate reactions to drugs. In Bellandur, it had reduced to just 17, implying that bacteria had gone up a few notches in their resistance to becoming completely resistant.
A point to note is that Mr. Mahesha and Ms. Jamwal chose the enterobacter family of bacteria for their tests. The study did not look at other bacteria species, whose resistance could also be a concern.
For Ms. Jamwal, the results show the emergence of new concerns and new pollutants which Sewage Treatment Plants are not capable of filtering. “There really has not been many studies in the city on the zone of influence of these antimicrobial resistant bacteria in lakes, or whether they end up in groundwater. Without in-depth studies, the State is pumping out the same water to Kolar where we don’t know the consequences,” she says.