Bacteria are rapidly emerging as a new class of “living medicines” used to kill cancer cells.

We’re still a long way from a “cure” for cancer.

But one day we could have programmable, self-navigating bacteria that find tumours, release treatment only where needed, then vanish without a trace.

Here’s where the science is up to.

Current treatments aren’t perfect

Many tumours are hard to treat. Sometimes, treatments cannot penetrate them. Other times, tumours can “fight back” by suppressing certain parts of the immune system, reducing the impact of treatments. Or tumours can develop resistance to treatments.

Using bacteria could overcome these obstacles.

More than a century ago, surgeons noticed some people with cancer who developed bacterial infections unexpectedly went into remission. That is, their cancer signs or symptoms decreased or disappeared.

Now we’re learning what could explain this. Broadly speaking, bacteria can activate the body’s immune system to attack cancer cells.

In fact, this approach is already used in the clinic. Bacteria are now the treatment of choice worldwide for certain cases of bladder cancer. When doctors deliver a weakened version of Mycobacterium bovis directly into the bladder through a catheter, the body’s immune response destroys the cancer.

Why bacteria?

Certain bacteria have an unusual talent. They can naturally find and grow inside solid tumours – ones that grow in organs and tissues – but leave healthy tissue relatively untouched.

Solid tumours are perfect homes for these bacteria as they contain lots of nutrients from dead cells, are low in oxygen (an environment these bacteria prefer), and typically have reduced immune function, so cannot defend themselves against the bacteria.

All this suggests possible careers for these bacteria as delivery couriers to carry targeted, anti-tumour therapies.

Over the past 30 years or so, more than 500 research papers, 70 clinical trials and 24 startup companies have focused on bacterial cancer therapy, with growth accelerating sharply in the past five years.

Most bacterial cancer therapies in clinical trials today target solid tumours, including pancreatic, lung, and head and neck cancers, which are the kinds that often resist conventional treatments.

Bacteria could deliver cancer vaccines

Cancer vaccines work by presenting a cancer’s unique molecular “fingerprints”, known as tumour antigens, to the immune system so it can hunt down and eliminate tumour cells displaying those antigens.

Bacteria can serve as couriers for these anti-cancer vaccines. Using genetic engineering, the genetic instructions (or DNA) in bacteria that might make us unwell can be removed and replaced with DNA for immune-stimulating tumour antigens.

Listeria monocytogenes is the main character in more than 30 cancer vaccine clinical trials. Unfortunately, most of these trials did not show that these treatments work better than current ones.

The challenge is teaching the immune system to recognise cancer’s telltale antigens strongly enough to remember them, without pushing the body into dangerous overdrive.

Bacteria could boost existing cancer therapies

Nearly half of current clinical trials using bacteria in cancer therapies pair bacteria with immunotherapies or chemotherapy as part of personalised treatment plans to enhance the body’s attack on cancer.

Various approaches have finished phase 2 clinical trials. These include using immunotherapy combined with modified Listeria to activate the immune system for recurrent cervical cancer.

Another trial used modified Salmonella in people with advanced pancreatic cancer alongside chemotherapy to increase survival.

Bacteria could be ‘bugs as drugs’

Arming bacteria with a drug means they could destroy the tumour from the inside, creating “bugs as drugs”.

For this, we need precise genetic control over how bacteria behave. Researchers can already reprogram bacteria to sense, compute and respond to molecular signals around the tumour.

Researchers can also engineer bacteria to self-destruct after delivering a drug, secrete immune-boosting molecules, or activate other therapies on command.

Researchers are building “multi-function” strains that combine several treatment strategies at once.

Probiotic species used in humans for many years are also candidates, including Escherichia coli Nissle, Lactobacillus and Bifidobacterium. These can be engineered to produce cancer-killing molecules or alter the environment around the tumour.

How close are we, really?

While early human trials have shown this approach is generally safe, finding the right dose remains a delicate balance.

Bacteria are also living entities that can evolve in unpredictable ways, and their use in humans demands strict safety controls. Even strains modified for safety can cause infection or trigger excessive inflammation.

So scientists are developing “biocontainment” strategies – engineered safeguards that prevent bacterial spread beyond tumours or triggers them to self-destruct after treatment.

If we can overcome these issues, such “living medicines” would still need to successfully complete clinical trials and receive regulatory approval before being commonly used in the clinic.

If so, this could mark a profound shift in how we treat cancer, from static drugs to adaptive biological systems.

Josephine Wright, Senior Research Fellow,, South Australian Health & Medical Research Institute and Susan Woods, Associate Professor, GESA Bushell Research Fellow, University of Adelaide and Principal Research Fellow, Precision Cancer Medicine, South Australian Health & Medical Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Everyone seems to have a different opinion when it comes to how often towels and bed sheets should be washed. While many people might wonder whether days or weeks is best, in one survey from the United Kingdom, almost half of single men reported not washing their sheets for up to four months at a time.

It’s fairly clear that four months is too long to leave it, but what is the ideal frequency?

Bed linen and towels are quite different and so should be washed at different intervals. While every week or two will generally suffice for sheets, towels are best washed every few days.

Anyway, who doesn’t love the feeling of a fresh set of sheets or the smell of a newly laundered towel?

Why you should wash towels more often

When you dry yourself, you deposit thousands of skin cells and millions of microbes onto the towel. And because you use your towel to dry yourself after a shower or bath, your towel is regularly damp.

You also deposit a hefty amount of dead skin, microbes, sweat and oils onto your sheets every night. But unless you’re a prolific night sweater, your bedding doesn’t get wet after a night’s sleep.

Towels are also made of a thicker material than sheets and therefore tend to stay damp for longer.

So what is it about the dampness that causes a problem? Wet towels are a breeding ground for bacteria and moulds. Moulds especially love damp environments. Although mould won’t necessarily be visible (you would need significant growth to be able to see it) this can lead to an unpleasant smell.

As well as odours, exposure to these microbes in your towels and sheets can cause asthma, allergic skin irritations, or other skin infections.

So what’s the ideal frequency?

For bedding, it really depends on factors such as whether you have a bath or shower just before going to bed, or if you fall into bed after a long, sweaty day and have your shower in the morning. You will need to wash your sheets more regularly in the latter case. As a rule of thumb, once a week or every two weeks should be fine.

Towels should ideally be washed more regularly – perhaps every few days – while your facecloth should be cleaned after every use. Because it gets completely wet, it will be wet for a longer time, and retain more skin cells and microbes.

Wash your towels at a high temperature (for example, 65°C) as that will kill many microbes. If you are conscious of saving energy, you can use a lower temperature and add a cup of vinegar to the wash. The vinegar will kill microbes and prevent bad smells from developing.

Clean your washing machine regularly and dry the fold in the rubber after every wash, as this is another place microbes like to grow.

Smelly towels

What if you regularly wash your towels, but they still smell bad? One of the reasons for this pong could be that you’ve left them in the washing machine too long after the wash. Especially if it was a warm wash cycle, the time they’re warm and damp will allow microbes to happily grow. Under lab conditions the number of these bacteria can double every 30 minutes.

It’s important to hang your towel out to dry after use and not to leave towels in the washing machine after the cycle has finished. If possible, hang your towels and bedding out in the sun. That will dry them quickly and thoroughly and will foster that lovely fresh, clean cotton smell. Using a dryer is a good alternative if the weather is bad, but outdoors in the sun is always better if possible.

Also, even if your towel is going to be washed, don’t throw a wet towel into the laundry basket, as the damp, dirty towel will be an ideal place for microbes to breed. By the time you get to doing your washing, the towel and the other laundry around it may have acquired a bad smell. And it can be difficult to get your towels smelling fresh again.

What about ‘self-cleaning’ sheets and towels?

Some companies sell “quick-dry” towels or “self-cleaning” towels and bedding. Quick-dry towels are made from synthetic materials that are weaved in a way to allow them to dry quickly. This would help prevent the growth of microbes and the bad smells that develop when towels are damp for long periods of time.

But the notion of self-cleaning products is more complicated. Most of these products contain nanosilver or copper, antibacterial metals that kill micro-organisms. The antibacterial compounds will stop the growth of bacteria and can be useful to limit smells and reduce the frequency with which you need to clean your sheets and towels.

However, they’re not going to remove dirt like oils, skin flakes and sweat. So as much as I would love the idea of sheets and towels that clean themselves, that’s not exactly what happens.

Also, excessive use of antimicrobials such as nanosilver can lead to microbes becoming resistant to them.

Rietie Venter, Associate professor, Clinical and Health Sciences, University of South Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.