Climate Change Raises Antibiotic Resistance In Common Pathogens

Climate change is increasing antibiotic resistance in bacteria like E. coli and Klebsiella, with rising temperatures and dry soil linked to higher resistance, says an expert. Climate pressures may fuel the spread of increasingly drug-resistant Salmonella.

BANGKOK, July 24 — Climate change may be making common bacterial infections harder to treat, as rising temperatures and other climate pressures contribute to the growing threat of antimicrobial resistance (AMR).

Higher temperatures have been linked to greater drug resistance in common bacteria including Escherichia coli, or E. coli, and Klebsiella, according to Dr Subramanian Swaminathan, director of infectious diseases at Gleneagles Hospital in Chennai and Bengaluru, India.

“For every 10 degrees Celsius rise in temperature, E. coli resistance goes up by 4.2 per cent. There is very good quality data here. For Klebsiella, it’s about 2.2 per cent. For Staph aureus, over 2.7 per cent,” Dr Subramanian told the Asia-Pacific International Roche Infectious Disease Symposium (APAC-IRIDS) 2026 here on July 8.

“So there is a direct correlation between temperature rise and drug resistance even in the community. You’re going to see more drug resistance in your common day-to-day gram negatives and gram positives going forward.”

Gram-negative and gram-positive bacteria are two broad categories of bacteria.

E. coli and Klebsiella, which are gram-negative, can cause infections including urinary tract, bloodstream, and lung infections, while the gram-positive Staphylococcus aureus can cause skin, bloodstream, and other serious infections.

The implications of a warming planet for infectious disease extend well beyond antibiotic resistance. Dr Subramanian said warming alone affects about 160 infectious disease processes, including the expansion of mosquito-borne diseases like dengue into new geographic areas and increased transmission of foodborne infections such as Salmonella.

Floods, storms, droughts, and changing rainfall patterns can also alter the spread of vector-borne, waterborne, airborne and foodborne diseases.

“We don’t own this world. Microbes do. They rule. We are here as renters at best. That’s the honest truth of it. And as the climate changes, the dynamics change. Pathogens will survive all kinds of events; we, not so much,” Dr Subramanian said.

Climate and infectious disease have long been associated with illnesses such as dengue, malaria, and leptospirosis. But emerging research suggests that climate conditions may also affect bacteria that are not traditionally thought of as weather-related.

“We don’t think of E. coli, Klebsiella, as a weather-related pathogen in the traditional sense. Probably not. But the data is saying something else and we have to understand this.”

Dr Subramanian said the relationship between climate change and antibiotic resistance can unfold in several ways.

Climate disruption can increase the overall number of infections, which in turn means more patients with drug-resistant infections. Population displacement after extreme weather events can strain resources and facilitate the transmission of resistant pathogens, while food insecurity and poor nutrition can leave people more vulnerable to infection.

Dr Subramanian also pointed to increasingly uneven rainfall patterns, where heavy downpours that are difficult to capture and store are followed by prolonged periods of water scarcity. Such extremes can disrupt sanitation and water supplies, creating conditions that increase the risk of infections and, in turn, antibiotic use.

Environmental contamination from industrialisation, urbanisation, and pharmaceutical industries can also contribute to antimicrobial resistance.

The Covid-19 pandemic offered an example of how a large-scale crisis can accelerate antibiotic use. Even as treatment protocols for the viral disease became established, Dr Subramanian said fear and uncertainty drove the use of antibiotics in communities and hospitals in many parts of the world.

“Covid probably saw the highest spike in antibiotic use in the community and in hospitals because of fear,” he said.

“Even when protocols were there saying, ‘Okay, this is where you give, say, remdesivir or steroids’, it always went with a little bit of antibiotics in many parts of the world.”

Dry Soil May Drive Bacteria To Develop Drug Resistance

Dr Subramanian highlighted emerging evidence that drought and drying soil may create environmental conditions that push bacteria to develop resistance mechanisms.

Soil naturally contains antimicrobial compounds, which are diluted when the ground is moist. As soil dries, those compounds become more concentrated, exposing bacteria to greater antimicrobial pressure and favouring those that can develop or carry resistance mechanisms.

“Droughts create the same kind of problem as overuse of antibiotics in a clinic,” Dr Subramanian said.

“When the soil dries up, these antimicrobial compounds get concentrated and therefore pathogens have to evolve drug resistance mechanisms to survive drying. And what do you have? A higher chance of drug-resistant infections. We have seen this with E. coli and Klebsiella. This is really scary.

“The soil is a great reservoir of organisms. It is also a reservoir for a lot of antimicrobial chemicals, naturally occurring and synthetic. And when this starts drying and you have loss of water in the soil, bacteria become more and more drug resistant,” he added.

Dr Subramanian said the implications could extend to countries that have traditionally had lower levels of antimicrobial resistance, as climate pressures create new conditions for resistance to emerge and spread.

“Places which have traditionally low levels of resistance will now start rising to meet the places which have high levels of resistance already.”

Warming may also accelerate the transfer of resistance genes between bacteria, while floods can spread contaminated water and resistant organisms across wider areas.

As infections become harder to treat and uncertainty grows over which drugs will work, greater antibiotic use could further fuel the cycle of resistance, Dr Subramanian said.

Salmonella Becoming ‘Nearly Impossible To Treat’

Dr Subramanian singled out Salmonella as a growing concern, particularly in India, where rising resistance is narrowing treatment options for an already common foodborne infection.

“For every one degree rise in temperature, there are five to 10 per cent more Salmonella cases. So a rise in temperature correlates with increased transmission of diseases like Salmonella,” he said.

Warmer temperatures and drought conditions can favour Salmonella growth and facilitate gene transfer between bacteria, accelerating the spread of resistance genes.

Dr Subramanian said antibiotic resistance in Salmonella has risen significantly over the past eight decades, with climate change estimated to account for at least 10 per cent of that change.

Genomic data suggest that resistant Salmonella may be evolving more rapidly in the Middle East, North Africa, South Asia and sub-Saharan Africa, he said.

“In my part of the world, Salmonella is becoming nearly impossible to treat,” Dr Subramanian said. “We now have the MBL gene in some strains of Salmonella and there are times when I have successfully used chloramphenicol.”

MBLs, or metallo-beta-lactamases, are enzymes that can make bacteria resistant to carbapenems, a class of powerful antibiotics often reserved for difficult-to-treat infections.

The shrinking arsenal has forced clinicians in some cases to reconsider older antibiotics. Dr Subramanian described chloramphenicol as his “secret weapon” as resistance erodes the effectiveness of commonly used treatments.

“Public health-wise, it’s a disaster because we are running out of antibiotics. Our first-line use in India used to be azithromycin and ceftriaxone. Now resistance to both is becoming more and more commonplace,” he said. “We are having to use something like chloramphenicol. Where do we go from here?”

The consequences are likely to fall disproportionately on lower-income countries, Dr Subramanian said, where health systems have fewer resources to absorb the cost and burden of increasingly difficult-to-treat infections.

“What we think is that this is going to be really, really bad by the year 2100 unless we do something about it,” he said. “As bad as climate change is, inertia is even worse. We simply don’t recognise the problem and we are unwilling to act on it.”

The effects of warming are not limited to bacteria and viruses. Dr Subramanian also pointed to Candida auris, a difficult-to-treat fungus whose tolerance of higher temperatures may help it spread as the climate warms.

He said C. auris is already a formidable pathogen because of its ability to form biofilms and rapidly develop resistance to antifungal drugs. A biofilm is a community of microbes that attaches to a surface and forms a protective layer, making it harder to eliminate.

‘One Country Alone Cannot Fix This’

The evidence linking climate change and antimicrobial resistance is growing, but Dr Subramanian cautioned that the relationship remains one of correlation rather than proven causation, with more research needed to understand the mechanisms at work.

“We need far more studies to understand how it exactly interacts with all of this and how it drives all of this,” he said.

Climate change is not the only environmental pressure that may shape resistance. Dr Subramanian cited research from the Paraná Delta in Argentina examining soils exposed to glyphosate, where researchers found drug resistance in the soil, with resistant strains and genes also detected in hospital patients.

“Having it in the community is worrying, but having it in the patient who comes to the hospital is scary,” he said.

The concern is not simply the loss of a single antibiotic, Dr Subramanian said. Environmental pressures may contribute to resistance across multiple classes of drugs used to treat common infections.

“You may lose cotrimoxazole, you may lose tetracyclines, you may lose some beta-lactams. Losing multiple antibiotics like that for easy-to-treat and common infections is a disaster.”

Addressing that threat will require interventions well beyond the clinic. Dr Subramanian called for climate-resilient health systems, better water management, stronger sanitation and hygiene, more responsible antimicrobial use and greater public awareness.

“The most effective intervention in public health is actually sanitation, good water supply and sewage disposal, not vaccination,” he said. “I mean vaccination is awesome, but not even close. Or, for that matter, antimicrobials.”

He said a One Health approach – bringing together human health, veterinary, agricultural, and environmental sectors – would be critical, alongside stronger surveillance networks and cooperation involving international bodies such as the Food and Agriculture Organization (FAO) and animal health organisations.

“One country alone cannot fix this. It has to be everybody working together. And we need a global plan.”

Dr Subramanian also called for better diagnostics and smarter use of existing diagnostic tools to reduce unnecessary antibiotic use and “collateral damage”, alongside vaccination and better control of underlying conditions such as diabetes.

“Climate change and AMR are not unrelated things, they are related,” he said. “And the more we research into this, the more we see that they are related mechanistically and they are co-evolving.”

The problem may be particularly difficult to reverse because some resistant bacteria can now survive and spread without the biological disadvantage, or “fitness cost”, once thought to accompany resistance.

“In India, if you look at it, 70 per cent of community-acquired E. coli and Klebsiella will be ESBL. So there’s really no fitness cost to be ESBL, and that is scary. And warming only makes this worse.”

ESBL-producing bacteria make enzymes that can render several commonly used antibiotics ineffective. Dr Subramanian’s point was that carrying these resistance mechanisms no longer appears to put the bacteria at a disadvantage, allowing them to continue surviving and spreading in the community.

For countries already carrying a disproportionate burden of antimicrobial resistance, Dr Subramanian said recognition of the problem is not enough.

“What we don’t need is a pat on the back. What we don’t need is an award saying, awesome job. We need help. We need to understand that we have to work on this together,” he said.

“We need to advocate and say this needs to be measured, this needs to be monitored, and this needs to be a priority.”