Dr Phil Kieran: I’m a GP and here’s why antibiotics aren’t always the answerThe more we use antibiotics, the more opportunities there are for these resistant strains to multiply and spread Tue, 08 Sep, 2026 – 11:52Dr Phil Kieran
Dr Phil Kieran is a full-time GP practising in Cork. He previously presented RTE’s ‘You Should Really See a Doctor’ and ‘How Long Will You Live?’.
“I just want to catch it before it gets worse”.
“I think it’s going down to my chest.”
“I always need an antibiotic doctor — my infections never leave of their own accord.”
These are the kind of statements I hear daily at my practice, and I am pretty sure that every GP around the country, if not the world, will report the same.
Most of us are aware that antibiotics should be prescribed sparingly and only when needed, and that they don’t help with viral infections.
However, I don’t think we as doctors are very good at explaining the reasons why.
Antibiotics kill or slow down specific bacteria which cause health problems. The unwelcome bacteria can be sensitive to the antibiotic, in which case it works, or they can be resistant to the antibiotic, meaning they often don’t even notice it.
It’s important to remember that we are referring to whether the bacteria are sensitive to the antibiotic, not the person.
Let’s look at how antibiotics work.
Most infection-causing bacteria have a cell wall. Penicillin and some other antibiotics interfere with building the wall, weakening the bacteria. It’s a bit like damaging the mortar in a brick wall, making it unstable. Use a different “mortar”, and the wall stays stable (antibiotic-resistance).
If the bacteria are sensitive to the antibiotic, they can no longer thrive, allowing the immune system to clear the bacteria. If the bacteria are resistant to the antibiotic, a different approach may be needed.
Every time you use an antibiotic, you kill bacteria that are sensitive to it.
Some resistant bacteria may survive, so the more we use antibiotics, the more opportunities there are for these resistant strains to multiply and spread to others. Over time, resistant strains of bacteria can become more common, meaning that the antibiotic may no longer work against infections caused by these bacteria.
Viruses operate completely differently. They use our cells to make more of themselves and do not build their own cell walls. Antibiotics won’t affect the virus.
Antibiotics will also kill bacteria in the gut, changing our gut microbiome and reducing the variety of good bacteria in it, which is far from ideal.
I can count on one hand the number of times my children have been on antibiotics.
They get sick as frequently as most children, but I am not keen to put them on a medication unless it’s necessary and if their GP says it’s reasonable to wait longer before treating them, I’m relieved that they don’t need antibiotics.
Antibiotics are one of the most amazing discoveries in history, but they are not always the answer.
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