How colistin went from ‘holy water’ in medicine to ‘sewage’ of resistance

More research is needed to find out the long-term effects of using colistin on humans

The practise of using antibiotics for promoting growth in animals is of great concern because it accounts for a significant portion of antibiotic use globally and poses a direct threat to human health by reducing the effectiveness of critical antibiotics. Photo: iStock

The rise of resistance to the antibiotic colistin represents a formidable threat to global public health. Colistin, which is sometimes called an “antibiotic of last resort”, is very important for treating serious infections caused by gram-negative bacteria that are very resistant to many drugs. In clinical settings, we treat colistin with the highest level of caution, reserving its use for cases where other antibiotics have failed.

However, the recent global rise in colistin resistance, particularly due to the spread of the mobilised colistin resistance gene, is alarming. This gene is often found on the mobile genetic elements of bacteria that live in livestock. It has been linked to the widespread use of colistin in agriculture, especially as a way to help plants grow. When these resistance genes jump from animals to humans, they can lead to treatment failures.

The World Antimicrobial Resistance Awareness Week takes place from November 18-24 every year.

Read more: Antimicrobial resistance: How factory farming is destroying our planet

The use of antibiotics to promote growth in livestock is a practice where sub-therapeutic doses of antibiotics are administered to healthy animals, which can also improve feed efficiency. While this practice has been beneficial for increasing production in the agricultural industry, it has also been widespread, particularly in intensive farming operations. 

The antibiotics used for growth promotion are often the same or belong to the same classes as those used to treat human infections. This extensive use has led to a selection pressure that favours the survival and spread of antibiotic-resistant bacteria, which can be transmitted from animals to humans through direct contact, the environment and the consumption of contaminated food products. 

The practise of using antibiotics for promoting growth is of great concern because it accounts for a significant portion of antibiotic use globally and poses a direct threat to human health by reducing the effectiveness of critical antibiotics.

In India, prior to 2018, the prevalence of colistin-resistant bacteria in the agricultural sector was not well documented. Recognising the dire implications of this knowledge gap, our interdisciplinary team of doctors and scientists embarked on a pivotal study.

Read more: Antimicrobial resistance: India needs waste management, process control to prevent antibiotic pollution

We tested poultry, fish, and vegetable samples for colistin-resistant bacteria and found a disturbingly high incidence. Findings from our study showed that the colistin-resistant genes in these samples were caused by using the antibiotic to help poultry grow.

The study extended to a group of young, healthy volunteers, among whom 14 per cent were found to be carriers of colistin-resistant bacteria in their gut flora. Genomic analyses confirmed that these bacteria were not of hospital origin but were associated with the same strains found in poultry.

The implementation of the ban on the commercial use of colistin for growth in 2019 marked a significant milestone in the fight against antibiotic resistance in India. This move has markedly curtailed the use of colistin as a growth promoter in the poultry industry. Still, we need to stay alert and do more research to find out what the long-term effects of using colistin and the resistance patterns among human populations.

The Chennai Declaration, an initiative aimed at curbing antibiotic resistance, played an instrumental role in bringing about this legislative change. Persistent efforts of the Chennai Declaration team, active  engagement with policymakers and interdisciplinary work of relevant ministries of the central government  were crucial in achieving the prohibition of colistin for growth promotion

Read more: Antimicrobial resistance: Here are some practices that can improve milk quality, cattle health

Looking forward, India’s commitment to antibiotic stewardship must extend beyond colistin, encompassing a range of medically important antibiotics that are still used as growth promoters. Continuing research, surveillance, and policy advocacy are critical to ensuring that the positive steps taken are reflected in reduced resistance rates and the protection of public health.

With its vast resources and intellectual capital, India is well-positioned to lead the development of sustainable practices in animal husbandry that do not compromise human health.

Abdul Ghafur is coordinator, Chennai Declaration and consultant in infectious diseases, Apollo Hospital, Chennai

Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth

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