David Felstead has spent much of the past six years being treated in hospital for a superbug infection in his left leg. After antibiotics stopped working, his health deteriorated and he faced the prospect of losing his limb.

The infection had taken hold around an implant fitted in his thigh, after the bone needed to be removed to treat bone cancer when he was just eight.

Over the years he underwent regular operations to extend the prosthetic to ensure his legs were the same length as he grew to his adult height of 6ft.

‘I can’t tell you how many operations I’ve had, maybe around 40,’ says David.

‘Every now and then I’d pick up infections, which would be treated with antibiotics.’

He avoided any major problems until 2020 when, aged 37, he got out of the shower ‘and saw a little hole in the skin on my thigh that was oozing liquid’, he recalls. ‘I hadn’t fallen so I didn’t know where it came from.’

Lab tests confirmed David had contracted E. coli and S. aureus bacterial infections, and he was prescribed antibiotics – first tablets and then intravenously in hospital.

‘I even underwent surgery to clear out the wound – but nothing seemed to get rid of it,’ he says. ‘I had abscesses so bad you can’t imagine the grimness of it.

‘As the infection progressed it was excruciating and I was exhausted all the time, sleeping for 12 hours a day.’

It got to the point where he couldn’t look after himself and David, who works in education, had to move from the Midlands to live with his parents in Kent.

As the strongest antibiotics failed to clear the infection, David’s doctors faced a stark choice: continue with further revision surgery that ‘clearly was not working – or amputate my leg’, he says.

Then came an unlikely option: killing the bacteria with viruses.

Phages – short for bacteriophages, meaning ‘bacteria eaters’ – are viruses that naturally infect and kill bacteria.

At a basic level, a phage attaches itself to a susceptible bacterium, injects its genetic material and hijacks the cell’s machinery to make copies of itself. The bacterium eventually bursts, releasing new phages that go on to infect other bacteria.

Phages have been studied for over a century, but interest is growing due to the threat of superbugs resistant to current medications.

More than 66,000 antibiotic-resistant infections were reported in England alone in 2024, and they are thought to contribute to around 35,200 deaths a year across the UK.

Each phage targets and kills a specific bacterium – this power can be harnessed as a single treatment, or doctors can mix different phages into ‘cocktails’ for more complicated infections.

They can also be used alongside antibiotics to maximise their effect, because they kill bacteria via different mechanisms.

The latest research even suggests phages can make ineffective antibiotics work again. For people with chronic infections, the promise is enormous.

‘For some patients with resistant chronic urinary tract infections (UTIs), respiratory infections, infected foot ulcers or bone infections, phage therapy could offer an option when antibiotics are no longer working effectively,’ says Martha Clokie, a professor of microbiology and director of the Becky Mayer Centre for Phage Research at the University of Leicester, and a leading UK expert in phage treatment.

‘We are seeing more interest from doctors who want to try phage therapy,’ she adds.

Under guidelines from the Medicines and Healthcare products Regulatory Agency (MHRA), unlicensed phage therapy is permitted on a compassionate basis, i.e. where there’s a clear clinical need, with their doctor responsible for overseeing its use.

However, getting access to phage therapy is still very difficult so it is generally only considered when it is a patient’s last resort.

When his doctor asked if he’d like to try phage treatment, David immediately agreed: ‘I like experiments and the idea of using something from nature,’ he says.

Phages are found everywhere where bacteria exist, including in our bodies and in the environment, such as soil or water.

And unlike viruses that cause illness, phages only target and kill bacteria. This means they are safe and to date have not been linked with significant side effects.

Despite being available only on compassionate grounds, there have been multiple case reports of patients in the UK being successfully treated with phage therapy.

A study last year by Ninewells Hospital in Dundee summarised the results of the first three patients they treated with phages for persistent infections around artificial joints.

‘Patient one’, aged 84, had a persistent infection with S. aureusbacteria around a hip replacement despite repeated surgery and antibiotics. Nine months after phages were administered, his wound remained healed, inflammatory markers were normal and he was walking independently.

‘Patient two’, aged 71, had a recurrent hip infection involving Klebsiella and Corynebacterium bacteria, which was treated with phages alongside surgery and antibiotics, but the wound reopened and the infection was unresolved.

‘Patient three’, 77, had a resistant infection with S. epidermidis bacteria after a knee replacement, but after phage treatment and antibiotics was pain-free with a ‘fully healed wound’ after six months.

‘These promising results hint at the potential for phage therapy to transform the care of chronic orthopaedic infections,’ the patients’ doctors wrote in the journal Antibiotics.

In a more recent case, reported in July this year, an 81-year-old man with a chronic S. aureus infection around a knee replacement given phages alongside surgery and antibiotics was much more mobile 18 months later – and, significantly, he avoided amputation, reported the journal ASM Case Reports. And the evidence is stacking up beyond individual case reports.

A review published in the International Journal of Antimicrobial Agents last year, based on 130 studies involving 1,115 patients with difficult-to-treat or antibiotic- resistant infections, found that 71 per cent showed ‘clinical improvement’ – for instance, improved symptoms and lower infection and inflammation markers. Remarkably, in 51 per cent the bacteria were eradicated.

Meanwhile, in a US trial published in January on 42 patients with S. aureus blood infections, 88 per cent of those given phages alongside antibiotics saw their infection either improve or clear completely, compared with 58 per cent given a placebo alongside antibiotics, reported the journal Open Forum Infectious Diseases.

And now three clinical trials are set to be launched in Europe: two will look at treating E. coli in UTIs, the other involves Staphylococcal infections in prosthetic joints.

Professor Clokie, who is involved in one of the UTI trials, says they will start next year.

The UK involvement in the research ‘is a game-changer’, says Dr Antonia Sagona, a reader of infection and microbiology at the University of Warwick.

‘It will help move phage therapy beyond isolated cases and towards a treatment that doctors can consider with greater confidence.’

However, despite the hope and promise, there is a catch: it takes time to identify the bacterium that causes an infection and then find the phage that kills it.

The latter involves contacting phage centres, often run by universities (including several in the UK), or searching online phage ‘banks’, where researchers worldwide log information about phages they have identified for others to use.

Then the phage has to be cultured and made into a pharmaceutical-grade product in a lab that meets Good Manufacturing Practice (GMP) standards – international rules designed to ensure medicines meet a required level of quality and safety.

And, crucially, the UK does not have a dedicated facility for this (though one is being developed, more on this later).

So currently a GMP or ‘GMP-like’ phage must be imported, says Dr Antonia Scobie, a consultant in infectious diseases and microbiology at Royal National Orthopaedic Hospital, who treated David and the 81-year-old whose case was reported in July.

She adds: ‘In David’s case the phage was found at Queen Astrid Military Hospital in Belgium – which has a phage therapy service – but further work was needed to produce the quality and quantity required. There were also hurdles around importing a live virus into the UK and securing the necessary approvals.’

Professor Clokie adds: ‘Currently it takes so long to get a phage treatment to a patient – months, even years – it’s horrible.’

Indeed it took a year for David to get the phage treatment. ‘It was always made clear that I wouldn’t get it quickly,’ he says, ‘but the process was frustrating as the infection was so debilitating’.

In fact, by the time the treatment became available, David’s infection was so severe his left leg had to be amputated just above the knee. This was done on June 15.

‘The risk of amputation had always been there – but the bigger risk was the infection spreading to the rest of my body, which would be life-threatening,’ says David, now 42.

To tackle the infection that remained in his leg, he had the first phage dose in early September.

‘They put catheters [thin, flexible tubes] into two areas in my thigh and administered the phages,’ he recalls. ‘It was strikingly undramatic.’

The treatment was given via an infusion directly into his thigh tissue twice daily (it took five minutes, he says), for seven days.

Phages are administered differently depending on the infection – an infusion is used for deep-seated infections around organs or prosthetics; with respiratory infections, the phages are inhaled through a nebuliser; and for wounds or ulcers they’re applied topically.

While currently patients are considered for phage therapy only for chronic infections, ‘in theory it’s possible phages could help people much earlier on in their infection journey’, says Dr Scobie, but sourcing phages and getting regulatory approval are hurdles to overcome.

A remaining challenge is that bacteria can become resistant to phages, although scientists are working to tackle this. One strategy is to combine several phages into a ‘cocktail’, increasing the chances that at least one will be able to attack the bacteria, explains Dr Sagona.

Phages can also be genetically modified, she says. ‘For example, we can modify the phage to make it better at entering human cells and targeting bacteria inside them.

‘It may even be possible to modify a phage so it can recognise two bacterial strains, for example both E. coli and salmonella [both commonly cause drug-resistant UTIs] rather than just one type.’

Another enticing prospect is that phage treatment can make previously ineffective antibiotics work again.

This is because some phages work by attaching to ‘pumps’ on the surface of bacteria that normally push out antibiotics before they attack the cell, explains Professor Clokie.

‘A common way for the bacteria to evade the phages is to alter or break the pumps they attach to – and this can make the bacteria sensitive to antibiotics again.’

She describes experiments at Yale School of Medicine in the US that have proven this, with patients with severe lung infections resistant to antibiotics.

‘When the patients were given a good dose of phage, they initially got a lot better,’ she says.

‘Eventually, the bacteria became resistant to phages – but by then they were sensitive to antibiotics again, so doctors finished their treatment with standard medication.’

Researchers say one of the biggest priorities now is to make the treatment easier to access in the UK – and to build the evidence needed to allow its approval for more routine use.

In September, an international group of experts published guidelines in Nature Medicine, setting out more than 60 recommendations – including the need for more trials, specialist laboratories and quality-controlled preparation of phages.

The UK has several university- based phage collections, including at Leicester, Exeter and Southampton.

‘If doctors send in their bacteria sample we can identify a potentially useful phage match within around two days,’ says Dr Franklin Nobrega, an associate professor of microbiology at the University of Southampton.

However, once identified, a phage still needs to be prepared as a pharmaceutical product at specialist facilities abroad.

Professor Clokie’s team at Leicester is working with the Precision Health Technology Accelerator, in Birmingham, which could be the UK’s first GMP production facility for phages.

‘In five years we’d hope to have phage therapy more readily available for doctors to access for their patients – most likely where there’s a high need, such as diabetic foot ulcers, UTIs and respiratory infections.’

But experts worry there is no agreed, standardised protocol for getting phages to patients.

Dr Scobie says: ‘There’s not even a recognised framework that means the NHS will pay for it, so even if we find a phage match that could save a patient, it rests on individual hospitals to find a way to fund it – which could be tens of thousands.’

‘There’s a sort of Catch-22 for phage therapy,’ adds Professor Clokie. ‘Doctors can’t use phages because there isn’t enough clinical trial data. You can’t get that clinical trial data unless you have phages made under GMP. But nobody wants to fund those production facilities in the UK unless there is clinical evidence.’

And producing GMP-compliant phages is very expensive, adds Dr Sagona. ‘A UK-based GMP facility would make things less expensive and much easier, but it would still be expensive,’ she says.

‘We’ve requested quotes from companies in Europe for research purposes and the cost can be £150,000 per sample. It would be too expensive to produce a personalised treatment for every patient.’

One way to overcome this cost is to develop off-the-shelf phage combinations that have been tested against the most common types of bacteria for each disease.

Dr Nobrega says: ‘We need stable, well-characterised cocktails that can be used as more general treatments, rather than having to start from scratch for every patient.’

His team is developing ready-made, off-the-shelf phage cocktails to target 80 per cent of the bacteria that cause UTIs.

‘If a cocktail works against a sufficiently broad range of the bacteria responsible for UTIs, for instance, it could potentially be developed as an off-the-shelf treatment for that condition,’ adds Dr Sagona.

‘The same approach could then be used for prosthetic joint or lung infections, and others.’

Dr Sagona’s team is working with Warwick Innovations, a spin-out of the University of Warwick, ‘to develop a phage cocktail for prosthetic joint infections’, she says.

In fact, off-the-shelf phage cocktails are already available across Europe, including in Georgia, the Czech Republic and Russia.

In Georgia, for example, broad-spectrum phage cocktails are sold through pharmacies for different conditions, including gut infections, UTIs and skin infections. ‘I know UK patients who travel to Georgia to buy these,’ says Dr Sagona.

In other European countries, including Belgium, doctors can prescribe personalised phages for individual patients, which are prepared in hospital pharmacies.

Professor Clokie, whose centre has the UK’s largest phage collection with over 3,500, adds: ‘We are working with Inteliphage, a Belgian company developing off-the-shelf and personalised phage products – together with a diagnostic test to help match phages to a patient’s infection.

‘It plans to launch in Belgium, the Netherlands, Germany and France – and is exploring UK access.’

It’s been over a month since David received his phage treatment and he’s waiting to find out whether it has helped.

‘I am adapting to my new life as an amputee while still fighting the infection,’ he says.

But his goal is clear: ‘I want to get back to working in the office – and once I have my new prosthetic leg early next year, I’ll move back to the Midlands and start getting my independence back.’