Colistin, one of the last remaining antibiotics that is still effective in killing bacteria and fighting infections like pneumonia, is rarely used in hospitals or clinics in Nigeria, and yet, samples from mothers and newborn babies already had colistin-resistant bacteria present – although neither the babies nor their mothers had been treated with colistin.
Writing in The Conversation, British researchers Kirsty Sands, Edward Portal, Owen Spiller and Timothy Walsh call for an end to antibiotic use in agriculture, having surmised that the mothers in their study may have picked up these colistin-resistant bacteria from the environment.
They write:
Life-threatening sepsis accounts, globally, for about 11m deaths – 20% of all deaths, per year, and affects children as well as adults.
In 2020, 2.4m newborn babies died of sepsis in the first month of their lives, many of them in sub-Saharan Africa. The main treatment for sepsis is antibiotics. However, the overuse and misuse of antibiotics in human medicine and agriculture has led to antimicrobial resistance – where bacteria, fungi and parasites have developed the ability to resist the action of medicines.
The WHO describes antimicrobial resistance as one of the top global public health and development threats.
This growing resistance is due to the overuse and misuse of antibiotics in both human medicine and in farming. They’re used in large quantities to grow crops and in animal feeds to treat and reduce the risk of infection in livestock.
It has been forecast that by 2050, more people will die from antimicrobial resistance than both cancer and diabetes combined.
Sub-Saharan Africa is one of the regions with the highest rates of deaths associated with antimicrobial resistance (including sepsis) in the world, with 23.5 deaths per 100 000 people.
Colistin is one of the last remaining antibiotics that is still effective in killing bacteria and fighting infections like pneumonia. It is deemed critically important for human medicine by the WHO.
We surmise that the mothers in our study may have picked up these colistin resistant bacteria from the environment. We cannot speculate on the specific mechanism.
The babies, meanwhile, could have picked up the bacteria from the hospital, the community, or from their mothers. It’s not yet known if these colistin-resistant bacteria stay in the mothers or babies, but if they do, this may increase their chances of acquiring future drug-resistant infections.
How we did our study
The samples from newborn babies and their mothers in our study were collected between 2015 and 2017 from three hospitals in Kano and Abuja. This research is the largest ever screening of intestinal microbiota for colistin resistance in Nigeria.
Of the 4 907 samples we analysed in our Cardiff and Oxford University laboratories, we found that 1% of samples had genes conferring colistin resistance across 41 mothers and eight babies. Although this is a low percentage, it is extremely worrying that any babies were carrying colistin-resistant bacteria within their first week of life.
Colistin is rarely used in hospitals and clinics in Nigeria. Therefore, our findings suggest that resistance may have emerged from the increasing use of colistin in agricultural settings in the country.
We are continuing our research with collaborators in Nigeria to further understand the levels of resistance in both the healthcare system and more broadly.
Dangers of antibiotics in agriculture
Globally, more antibiotics are prescribed to animals than to humans. Most of this consumption is not to treat infections; rather, it is to prevent infections or promote faster growth in animals.
In 2016, mobile colistin (mcr) genes were discovered in E. coli bacteria from a pig farm in China. These genes carry resistance to the antibiotic colistin, and can spread between bacteria, furthering colistin resistance.
This discovery led to a total ban on colistin’s agricultural use in China.
In February 2022, European laws were expanded to make it illegal to add antibiotics to livestock feeds as a precaution to prevent infections before they start.
However, in a study we published in 2023, we found that, while European countries have banned the use of colistin in farming, paradoxically they still actively export livestock feeds that contain colistin to low- and middle-income countries, such as Nigeria, for agriculture use.
It seems a highly questionable practice to knowingly profit by selling feedstuffs banned for use in Europe to developing countries that lack these regulations – particularly when these countries already suffer from some of the highest rates globally of endemic antimicrobial resistance for common antibiotics and treatment alternatives are either prohibitively expensive or completely inaccessible.
Estimates suggest that globally, almost 100 000 tons of antibiotics were used to raise cattle, sheep, chickens, and pigs in 2022. This usage is expected to increase by another 8% by 2030 and will lead to a direct increase in antibiotic-resistant infections.
Call for a total ban
There needs to be a global ban on colistin’s indiscriminate agricultural use to preserve this crucial antibiotic for when it is urgently required.
However, this is a delicate balance. A ban without alternative solutions may affect food production and adversely affect farmers’ livelihoods in already challenging climates.
And, with the world’s population set to increase by about 2bn by 2050, demand for affordable meat will only rise.
Urgent investment is also needed in hospital infection prevention and control programmes and improved water, sanitation and hygiene facilities in farms to help to limit the spread of antibiotic-resistant bacteria around these environments.
Animals should be given antibiotics only when they are sick. These antibiotics should be selected from those the WHO has listed as being “least important” to human health rather than from those classified as “highest priority/critically important”.
In September 2024, during the UN General Assembly in New York, leaders from governments, industry, financial institutions and scientific organisations will come together for a high-level meeting on antimicrobial resistance.
This event offers a timely opportunity for global leaders to set some targets to reduce antibiotic use in farming and support farmers in low- and middle-income countries to improve farm hygiene practices.
Kirsty Sands, Scientific Lead, Global Surveillance of Antimicrobial Resistance Research, University of Oxford; Edward AR Portal, Post Doctoral Research Associate, University of Oxford; Owen Spiller, Head of Medical Microbiology, Cardiff University; Timothy Walsh, Professor of Medical Microbiology, University of Oxford.
Study details
Characterisation of colistin resistance in Gram-negative microbiota of pregnant women and neonates in Nigeria
E. Portal, K. Sands, C. Farley, O. B. Spiller et al.
Published in Nature Communications on 14 March 2024
Abstract
A mobile colistin resistance gene mcr was first reported in 2016 in China and has since been found with increasing prevalence across South-East Asia. Here we survey the presence of mcr genes in 4907 rectal swabs from mothers and neonates from three hospital sites across Nigeria; a country with limited availability or history of colistin use clinically. Forty mother and seven neonatal swabs carried mcr genes in a range of bacterial species: 46 Enterobacter spp. and single isolates of; Shigella, E. coli and Klebsiella quasipneumoniae. Ninety percent of the genes were mcr-10 (n = 45) we also found mcr-1 (n = 3) and mcr-9 (n = 1). While the prevalence during this collection (2015-2016) was low, the widespread diversity of mcr-gene type and range of bacterial species in this sentinel population sampling is concerning. It suggests that agricultural colistin use was likely encouraging sustainment of mcr-positive isolates in the community and implementation of medical colistin use will rapidly select and expand resistant isolates.
See more from MedicalBrief archives:
WHO antimicrobials list ‘for humans only’
AMR burden weighs heavily on Africa – global study
Afro-European partnership in quest to tackle AMR