Most of us think infections come from outside invaders; harmful germs that enter the body and make us sick.
However, some microbes of growing concern are not strangers; they are long-term residents of our own bodies.
The human body is like a busy neighbourhood, home to trillions of microorganisms, including bacteria, fungi, and viruses.
Together, they form what scientists call the microbiome. Most of these tiny residents are not enemies. They help digest food, strengthen the immune system, and protect us from harmful germs.
For the most part, we live peacefully with these microbes. But when this delicate balance is disturbed, some of our friendly neighbours can become opportunistic pathogens.
In the age of antimicrobial resistance (AMR), these once-manageable microbes are becoming increasingly difficult to control.
Take Escherichia coli (E coli), for example. It normally lives in our intestines and plays an important role in maintaining gut health. But if it enters the urinary tract, it can cause infection.
Until recently, these infections were usually easy to treat. Today, many E coli strains no longer respond to commonly used antibiotics.
According to a landmark study published in The Lancet in 2022, six leading pathogens collectively accounted for nearly 1 million AMR-attributable deaths in 2019, with E coli being the single largest individual contributor.
The same is true for Candida, a fungus that normally lives quietly in our mouths and digestive system. Most of the time, it causes no harm. But when the immune system is weakened by illness, cancer treatment, or prolonged antibiotic use, it can multiply rapidly and cause serious, sometimes life-threatening, infections.
Another example is Staphylococcus aureus, a bacterium commonly found on our skin and inside the nose. Many people carry it without ever becoming ill.
However, some strains have evolved resistance to important antibiotics, making infections much more difficult and costly to treat.
What is driving this transformation?
One of the biggest reasons is the misuse and overuse of antibiotics. Every time antibiotics are taken unnecessarily, used incorrectly, or stopped too early, bacteria are given another opportunity to adapt.
Over time, they develop ways to survive medicines that once killed them.
In a sense, we are unintentionally training our microscopic neighbours to defend themselves.
This is no longer just a concern for scientists and doctors; it is a growing global public health problem.
In Bangladesh, this problem is easy to observe in everyday life. A parent may visit a local pharmacy for a child with a fever or a common cold and receive an antibiotic without a prescription, even though many of these illnesses are caused by viruses, against which antibiotics do not work.
While this may seem like a quick solution, repeated unnecessary use encourages bacteria to become resistant.
Studies have shown that antibiotics are frequently purchased without a prescription in Bangladesh, highlighting the urgent need for stronger antibiotic stewardship and greater public awareness.
According to the World Health Organization (WHO), the misuse and overuse of antibiotics are among the leading drivers of antimicrobial resistance worldwide.
The consequences affect all of us
Resistant infections lead to longer hospital stays, higher healthcare costs, and fewer treatment options. They also threaten many of the medical advances we now take for granted.
Safe surgery, cancer treatment, intensive care, and the care of newborn babies all depend on antibiotics that work.
The answer is not to eliminate the microbes that live with us. Most are essential for our health.
Instead, we must preserve the delicate balance between humans and the microorganisms that share our bodies.
That requires responsible antibiotic use, stronger infection prevention, better public awareness, and effective antimicrobial stewardship programs.
Healthcare professionals, policy-makers, pharmacists, and the public all have important roles to play.
Antimicrobial resistance is often called a silent pandemic because it spreads quietly, without the dramatic headlines of outbreaks like Covid-19. Yet its impact could be just as devastating.
The World Health Organization has identified AMR as one of the top 10 global public health threats facing humanity. The microbes that have lived alongside us need not become our enemies. Whether they remain trusted neighbours or dangerous adversaries will depend largely on the choices we make today.
ASM Tarik Hasan is a public health researcher specializing in antimicrobial resistance and clinical microbiology.
