Updated: May 16, 2021 7:38:58 pm
A SURVEILLANCE of microbes in wastewater across sewage treatment plants, points along Sabarmati river, and lakes in Ahmedabad city by researchers at the Indian Institute of Technology, Gandhinagar (IIT-Gn), has indicated an increased resistance to antibiotic drugs.
A major driver in the recent trend of the drug resistance, IIT-Gn researchers suspect, could be the abundant prescription of antibiotics during the pandemic, as compared to pre-Covid-19 period in 2018.
Drugs, which do not metabolise in the body, are often expelled out as it is or as a by-product in the form of bodily waste, such as excreta and urine, and this faecal matter mixes in wastewater through the sewer system. Not only faecal matter, but improper disposal of unused or expired drugs in households and hospitals, also end up in wastewater, professor Manish Kumar of Discipline of Earth Sciences division at IIT-Gn and the lead author of the latest study said.
At wastewater treatment plants (WWTP), if the clearing rate, that is, level of purification or filtration of microbial content is low, microorganisms exposed to antimicrobial drugs and metabolites develop mutations causing resistance to the drug.
Antibiotics are used to treat bacterial infections. A World Health Organisation (WHO) factsheet from July 2020 had warned that “a growing list of infections – such as pneumonia, tuberculosis, blood poisoning, gonorrhoea, and food-borne diseases – were becoming harder, and sometimes impossible, to treat as antibiotics become less effective”.
As a UK-based review of data from Covid-19 cases, mostly in Asia, found more than 70 per cent of patients received antimicrobial treatment despite less than 10 per cent on average having bacterial or fungal co-infections.
As the conventional treatment processes at WWTPs do not completely break down the parent antimicrobial drugs that leaches through faecal waste, it may instead generate some residues, metabolites or transformation products with similar biological activity as the parent drugs, making WWTPs hotspots for the spread of antidrug resistance.
In a possible first-of-its-kind study globally, where prevalence of antibiotic resistance in wastewater was seen in a Covid-19 context, water samples were collected from six different locations of Ahmedabad city on June 23, 2018, and October 16, 2020, which included two locations on the stretch of Sabarmati river (Nehru bridge and Sardar bridge), two lakes (Kankariya and Chandola), and two WWTP locations (Chandkheda and Vasna). Samples were collected from the influent untreated wastewater and effluent treated water.
E-coli, a coliform bacterium that is found in the lower part of large intestine and also in faecal matter, was isolated from the water samples and these isolated cultures were then checked against six specific antibiotic drugs to determine the susceptibility — whether bacterial culture growth was inhibited by the antibiotics, indicating good function of the drug or whether growth went unchecked, indicating resistance against the antibiotic.
The six drugs included three non-fluoroquinolone drugs — kanamycin (an antibiotic used to treat severe bacterial infections and tuberculosis), tetracycline (currently widely prescribed doxycycline, which is also a part of Uttar Pradesh’s issued treatment protocol, and belongs to the tetracycline class, used to treat bacterial pneumonia), sulfamethoxazole (used for bacterial infections such as urinary tract infections, bronchitis).
The three other drugs are fluoroquinolone — norfloxacin (used to treat urinary tract infections, gynaecological infections, inflammation of the prostate gland, gonorrhea and bladder infection), ciprofloxacin (used to treat chest infections, including pneumonia) and levofloxacin.
The study has found that broadly there is an increase in resistance for nearly all antibiotics except kanamycin, in 2020 vis-a-vis 2018, across all the six sites. At one of the WWTP effluent points, that is the treated water, resistance was shown of two fluoroquinolone drugs — ciprofloxacin and norfloxacin.
“The high resistance towards quinolone drugs is attributed to the discharge having domestic origin, because these drugs are prescribed for treatments of respiratory and urinary tract infections, their use has increased significantly during the Covid-19 pandemic,” the study hypothesises.
Overall, the three fluoroquinolone drugs showed less resistance as compared to the non-fluoroquinolone drugs.
The study states that an “increased pharmaceutical pollution during Covid-19 spread can increase environmental stress on bacteria or microbes causing more mutation” and result in genetic mutations and mechanistically resistant pathways in the infecting bacteria, making it resistant against particular antibiotics. “Thus, the highly infected regions or hotspots of Covid-19 spread around the globe have a greater probability of emergence of superbugs having multidrug resistance. Drugs like Remdesivir, Ivermectin, Azithromycin, Favipiravir, Chloroquine, Umiferovir, Ritonavir, Aspirin, and Hydroxychloroquine are going to remain under scanner,” the study warns.
It also found that the E-coli prevalence, especially at the two sewage treatment plants, was higher in 2020 as compared to 2018, which Prof Kumar said “could be because of the reduced industrial wastewater, which otherwise provides a hard environment for E-coli to survive”.
Kumar stressed that disinfection and water treatment processes at STPs “should be fine-tuned and advanced by UV radiation so as to reduce the E-coli prevalence”, as it otherwise poses a public health risk.
Overall, the study also finds that though the prevalence of E-coli was highest in 2018, more antibiotic-resistant E-coli were generated in 2020 and attributes it to “heavy usage of antimicrobials”.
Kumar said this is only a preliminary foundational base of a study and more thorough and conclusive results can be arrived at by doing resistant placid study through DNA sequence analysis of samples as well as a continued monitoring over time of pharmaceutical concentrations in urban waterbodies and while also checking for response in microbial drug-resistance.
Antimicrobial drug resistance, Kumar warns, “is a global phenomenon with potential to cause Covid-19 like chaos in near future”.
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