In a breakthrough, scientists have identified that bacteria can change form to avoid being detected by antibiotics in the human body. The study is published in the journal ‘Nature Communication’.
The World Health Organisation has identified antibiotic resistance as one of the biggest threats to global health, food security, and development. Studying samples from elderly patients with recurring urinary tract infections, the Newcastle University team used state-of-the-art techniques to identify that bacteria can lose their cell wall – the common target of many groups of antibiotics.
“Imagine that the wall is like the bacteria wearing a high-vis jacket. This gives them a regular shape (for example a rod or a sphere), making them strong and protecting them but also makes them highly visible — particularly to the human immune system and antibiotics like penicillin, said Dr Katarzyna Mickiewicz researcher at Newcastle University.
“What we have seen is that in the presence of antibiotics, the bacteria can change from a highly regular walled form to a completely random, cell wall-deficient L-form state– in effect, shedding the yellow jacket and hiding it inside themselves. In this form the body can’t easily recognise the bacteria so doesn’t attack them – and neither do antibiotics,” he added.
The research used samples obtained through a collaboration with clinicians at the Newcastle Freeman Hospital part of Newcastle upon Tyne Hospitals Foundation Trust organised by Dr Phillip Aldridge and Dr Judith Hall. The research shows that when antibiotics are present as in a patient with a UTI receiving penicillin or other cell wall-targeting antibiotic, then the bacteria can change the form, losing the cell wall which is often the target of the antibiotic.
The Errington team earlier demonstrated that our immune system can also induce L-form switching to some extent but treatment with antibiotics has a much more profound effect. The current study shows that L-forms of various bacterial species typically associated with UTIs including E. coli, Enterococcus, Enterobacter and Staphylococcus were detectable in 29 out of 30 patients involved in the study. In this L-form the bacteria are flimsy and weaker but some survive, hiding inside the body.
Also, the research has been video graphed for the first time. In the video, L-form bacteria isolated from a patient with UTI re-forming a cell wall after the antibiotic had gone taking just five hours. The team was also able to show by direct microscopy in the transparent zebrafish model, that the L-form switching is possible in the context of a whole living organism and not only in artificial conditions in the lab.
Dr Mickiewicz explained: “In a healthy patient this would probably mean that the L-form bacteria left would be destroyed by their hosts’ immune system. But in a weakened or elderly patient, like in our samples, the L-form bacteria can survive. They can then re-form their cell wall and the patient is yet again faced with another infection. And this may well be one of the main reasons why we see people with recurring UTIs.
“For doctors, this may mean considering a combination treatment – so an antibiotic that attacks the cell wall then a different type for any hidden L-form bacteria, so one that targets the RNA or DNA inside or even the surrounding membrane,” he added.

Source: Science Daily, ET Healthworld.

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