Bacteria communicate through a process called horizontal gene transfer, where they literally pass pieces of genetic material to each other.
Published Nov 20, 2025 | 7:00 AM ⚊ Updated Nov 20, 2025 | 7:00 AM
Representative image of antibiotic drugs. Credit: iStock
Synopsis: A Lancet study reveals 83% of Indians carry antibiotic-resistant bacteria (highest globally) due to incomplete courses and unaware overuse. Patients stop medicines once symptoms fade, allowing surviving bacteria to share resistance genes. Experts warn: finishing the full course is critical to prevent bacterial resistance; most early fevers are viral and need no antibiotics.
You wake up on day four of antibiotics and feel remarkably better. The fever has broken, the pain has subsided, and energy is returning. The pill bottle still holds four more days of medication, but you think: why keep taking medicine when I’m already cured? You toss the bottle in a drawer and move on with your life.
What you don’t realise is that you’ve just enrolled bacteria in a survival training program, and they’re learning fast.
A landmark study published in Lancet eClinicalMedicine reveals that 83 percent of Indian patients now carry antibiotic-resistant bacteria in their bodies, the highest rate among all countries studied.
Researchers at AIG Hospitals in Hyderabad compared India with Italy, the United States, and the Netherlands, finding that incomplete antibiotic courses represent one of the two biggest drivers of this crisis.
The other is unnecessary use, but the incomplete course problem proves particularly insidious because people genuinely believe they’re doing the right thing by stopping medicine once symptoms improve.
Dr D. Nageshwar Reddy, Chairman of AIG Hospitals and lead author of the study, identifies this behavior as central to India’s resistance crisis.
“Unnecessary use and incomplete use are the two biggest drivers of resistance. Some people start taking antibiotics, and the moment their diarrhoea or fever reduces—after just one day—they stop taking the medicine. But bacteria are clever. They pick up resistance genes and transmit them to other bacteria. Soon, all of them become resistant, and the next time the antibiotic will not work.”
Understanding why completing the course matters requires looking at what antibiotics actually do. When you take the first dose of an antibiotic, it doesn’t kill all bacteria instantly. It kills the weakest ones first—the bacteria most susceptible to that particular drug. If the infection involved millions of bacteria, maybe that first dose eliminates 90 percent of them. You feel dramatically better because the overwhelming bacterial load has dropped.
But that remaining 10 percent weren’t killed for a reason. They possessed slightly different genetic characteristics that made them more resistant to the antibiotic. Maybe their cell walls were thicker, or they had enzymes that could partially break down the drug, or they had pumps that could expel the antibiotic from their cells. These survivors are the bacteria that were always going to be hardest to kill.
When you continue the antibiotic course for the full prescribed duration, you maintain a high enough drug concentration in your body to kill even these tougher bacteria. The second, third, and fourth days of antibiotics aren’t redundant—they’re specifically targeting the survivors that the first doses couldn’t eliminate.
But when you stop at day three because you feel better, those resistant survivors remain alive in your body. They’ve been exposed to the antibiotic and survived. They’ve passed a test. And bacteria have a remarkable ability that humans don’t: they can share their test answers with their classmates.
Bacteria communicate through a process called horizontal gene transfer, where they literally pass pieces of genetic material to each other. A bacterium that survived antibiotic exposure can transfer the genes responsible for its resistance to completely different species of bacteria in your gut, your throat, or anywhere else in your body.
Dr Reddy explained this mechanism in vivid terms. “One important feature of bacteria is that they exchange genes with each other. So if one bacterium carries a gene that makes it resistant to antibiotics, it can pass that gene on to others. They are not selfish with each other—but they are selfish when inside the human body. Once a resistant bacterium enters, it spreads its resistance genes widely.”
He compared it to social contagion. “It’s like having one bad person in a society: they influence everyone else. There is no ‘visa’ needed—any bacterium can enter the body and spread these resistance genes. That is why resistant bacteria are now spreading so widely.”
This means that stopping your antibiotic course early doesn’t just leave some resistant bacteria alive in your body. It creates a training facility where those bacteria teach all their neighbours how to survive antibiotics. You become a walking incubator for resistance, and the next time you or someone else needs antibiotics, they might not work.
The AIG study uncovered something particularly troubling about antibiotic use in India. When researchers asked participants whether they had recently used antibiotics, patients in Italy, the Netherlands, and the USA reported 40 percent, 30 percent, and 8 percent recent use respectively. These numbers helped explain some of their resistance levels.
But in India, despite having by far the highest resistance rate at 83 percent, not a single patient reported recent antibiotic use.
Dr Reddy identified why this disconnect matters.
“So how is it that they claim they did not use antibiotics, yet resistance is extremely high? This means two things. First, many people simply do not know whether they have taken antibiotics. This is very common in India. You go to a medical shop with a fever, and the pharmacist gives you an antibiotic without explaining what it is. The patient has no idea they have taken one. This is dangerous because people are receiving antibiotics without their knowledge.”
If you don’t even know you’ve taken an antibiotic, you certainly can’t complete the course properly. The pharmacy might have given you a three-day supply when you needed seven days, or you might have taken the pills irregularly because you thought they were fever reducers rather than antibiotics. This knowledge gap means that even well-intentioned people who would complete a prescribed course are inadvertently contributing to resistance.
Beyond incomplete courses, Dr Reddy identified another concerning pattern: people taking antibiotics prophylactically before they’re even sick. “I even know people who take antibiotics before travelling, as ‘prophylaxis,’ which is completely wrong.”
This practice creates resistance without even treating an actual infection. The person takes a few days of antibiotics, feels fine (because they weren’t sick in the first place), and stops. Meanwhile, their normal bacterial population has been exposed to the drug, creating selection pressure for resistance without any medical benefit.
The misuse extends beyond individual behavior into systemic problems. “The two main causes of misuse are: unnecessary use—people take antibiotics for all fevers, even when not needed—and incomplete use,” Dr Reddy summarised. Both patterns work together to accelerate resistance development.
A critical gap in public understanding involves distinguishing bacterial infections from viral infections. Dr Reddy emphasised this point repeatedly: “Most fevers, coughs, and colds for the first three days are viral and do not need antibiotics. Doctors must act in a uniform manner and say clearly: ‘If the fever is less than three days, no antibiotics.'”
Antibiotics kill bacteria. They have zero effect on viruses. Taking an antibiotic for a viral cold is like trying to fix a broken computer by hammering nails into it—you’re using the wrong tool for the problem, and you’re causing additional damage in the process.
When someone takes antibiotics for a viral infection, several bad things happen simultaneously.
First, the antibiotic doesn’t help with the viral infection at all, so the person doesn’t get better any faster than they would have without it. Second, the antibiotic kills beneficial bacteria in their gut and elsewhere in the body, potentially causing side effects like diarrhea. Third, and most importantly for the resistance crisis, it creates selection pressure that allows resistant bacteria to proliferate.
“Patients come with just one day of fever and demand antibiotics,” Dr Reddy observed.
This demand pressure on doctors creates a difficult situation where medical professionals sometimes prescribe antibiotics they know are unnecessary because patients expect them or might seek treatment elsewhere if refused.
(Edited by Amit Vasudev)
