Unwelcome colonisers: biofilm formation on voice prostheses

ResearchBlogging.orgDiagram_showing_the_position_of_the_stoma_after_a_laryngectomy_CRUK_361.svgA human being’s voice is one of their most distinguishing and individual features. Most of us have experienced the frustration of temporarily losing our voices – but for many survivors of laryngeal cancer (cancer of the voice box), this loss is permanent. A laryngectomy, or full removal of the larynx, is a common last resort to treat this cancer if other options have failed. This operation disconnects the windpipe from the nose and mouth, leaving the patient to breathe through a hole in their neck called a stoma. The side effect of this operation, however, is that patients lose the ability to speak.

The challenge of giving these patients a voice has been partially solved; voice prostheses (VP) have been developed to allow people without larynges to speak again, albeit on a severely limited scale. A VP is a one-way valve that is placed into a puncture between esophagus and windpipe. If the stoma is covered, this valve allows air to escape through the esophagus and the mouth. With considerable training, people can then use this air to produce sounds in a variety of manners. An example of voice prosthesis speech can be heard in this video.

Voice prostheses are not without their problems. Biofilms – a sticky mass of microbes – clog the prostheses’ valve, preventing it from fully opening or closing. Saliva, microbes and other particles can leak into the windpipe and the trachea, where they can cause infections and dangerous diseases such as aspiration pneumonia. Candida albicans, one of the most common species of yeast in VP biofilms, is also capable of penetrating into the silicone of the device, eventually rendering it completely unusable. Together, these issues mean that VP lifespan is shortened dramatically – in some patients, prostheses may only last a few weeks. Most patients then require further valve replacement surgery.  The picture below shows a valve only three months after insertion.Valves

A team of researchers, led by Dr Campbell Gourlay, a molecular cell biologist at the University of Kent, and Professor Fritz Mühlschlegel, a Consultant Microbiologist at East Kent University Hospital Trust, are working to understand how best to stop the formation of biofilms on voice prostheses. Dr Gourlay explains that these biofilms are formed by organisms that live naturally in our mouth. These microbes pose no threat to us as long as our immune system functions properly and keeps them in check. However, the chemotherapy that patients receive to treat their cancer tends to leave them severely immunocompromised. Under these conditions, microbes can grow and multiply rapidly on the voice prostheses, forming biofilms where they might not be able to in a healthy individual.

It is not completely understood why voice prostheses – and other artificial objects in patients’ bodies, such as catheters – are such attractive places for biofilms to form. One contributing factor is that the surfaces of such devices are generally made of silicone, a material with excellent mechanical properties that is easily molded and that looks very smooth to our eyes. However, high-resolution microscopy conducted by Dr Gourlay’s group reveals that at the microbial scale, silicone surfaces look more like mountain ranges, with numerous peaks and valleys for microbes to attach to.

Recent studies have shown that there are other exacerbating factors. For example, C. albicans becomes better able to colonise surfaces in CO2-rich environments, such as those provided by exhaled breath. Furthermore, environments that experience shaking and friction are more easily colonised by biofilms than calmer areas. This seems counterintuitive at first, but such stresses cause microbes to release adhesive proteins in greater number to better enable them to cling to surfaces.

In a recent review in the Journal of Medical Microbiology, Dr Gourlay and his colleagues review some recent avenues of research. Among others, researchers are looking into surface coatings that could delay the onset and growth of biofilms. Metals such as palladium, titanium or even gold are being used, but it has not been conclusively shown that these coatings significantly reduce biofilm formation. Other options include coatings made from compounds with disinfectant or hydrophobic properties. So far, such methods are simply not cost-effective as they multiply the cost of a prosthesis but, on average, only extend its lifetime by a few weeks. Dr Gourlay suggests that ceramics may be of the more promising materials: they are smoother than silicone, extremely durable and less expensive than rare metal coatings.

Fortunately, there are far simpler ways in which VP users themselves can extend the lifetime of their device. A study has shown that prostheses in India tend to last much longer than in other countries. One possible explanation for this finding is that buttermilk, which is slightly acidic and has potential anti-microbial properties, may be an example of the strong influence that diet can have upon biofilm formation. Further research into the diet of laryngectomy patients and its impact on VP longevity will reveal whether the old adage ‘we are what we eat’ can be applied in this case.

The research Dr Gourlay and his team undertake is likely to have beneficial spillover effects for other indwelling surgical devices. A major research and development centre for VP devices has also recently been established. Along with simple nutritional changes that prolong prosthesis lifetime, the future of their users is hopefully set to become brighter, easier and more comfortable.

Jon Fuhrmann

Talpaert, M., Balfour, A., Stevens, S., Baker, M., Muhlschlegel, F., & Gourlay, C. (2014). Candida Biofilm Formation on Voice Prostheses Journal of Medical Microbiology DOI: 10.1099/jmm.0.078717-0

Image Credit:
Top: Cancer Research UK/Wikimedia Commons under CC BY-SA 4.0
Middle: Talpaert et al 2014.
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New to Science – September Edition

Sagardotegian_txotxetik_edatenEach month, the Society for General Microbiology publishes the International Journal of Systematic and Evolutionary Microbiology, which details newly discovered species of bacteria, fungi and protists. Here are a few of the new species that have been discovered, and the places they’ve been found. The full papers are available to journal subscribers, but the abstracts are free to read.

The summer holiday period is slowly drawing to a close, and laboratories, offices and universities around the world are returning to business as usual. Inevitably, though, the talk tends to turn to the exotic – or not-so-exotic – places we visited over the holidays.

While we may wax lyrical about the far-flung and extravagant places, for many researchers these locations are simply their everyday workplace. This month, we are introduced to a good many newly discovered microbes that are the fruit of these researchers’ labour. In the Tengger desert in northeast China, for example, a team of Chinese and American researchers have isolated Actinophytocola gilvus from a sample of soil crust. In the westernmost reaches of the country, Chinese scientists teamed up with Indian colleagues to identify Rhizobium populi from a desert poplar, a type of willow tree. Continue reading

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Under pressure: how do microbes grow in compacted soil?

10461205436_ba74732d94_zThis week, the Society for General Microbiology is hosting its first ever Focused Meeting, a mini-conference specialising on a specific topic within microbiology. This incarnation of the event is themed Emerging Challenges and Opportunities in Soil Microbiology and is taking place at the University of Loughborough. Jon Fuhrmann spoke to Archana Juyal, a PhD student from Abertay University in Dundee and a speaker at the event, about her research.

Archana is interested in how the structure of soil – including factors such as its density, stability and porosity – controls the distribution and functioning of the bacteria that live in it. She notes that microbes play a crucial role in this ecosystem, regulating over 80% of all chemical reactions taking place in soil. These reactions break down complex chemical compounds, producing essential nutrients for plants and soil-dwelling animals.

Even relatively small changes in soil structure can have an important impact on soil microbial communities. For example, bacteria introduced into farmland soil to enhance crop growth may require certain conditions in order to function. This is because soil, far from being a continuous solid, consists of a multitude of tiny particles called aggregates. These aggregates are separated by gaps, known as pores, which allow nutrients, water and other essential chemicals to be distributed within the soil so that they are available for microbes, plants and animals to use. Continue reading

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Nitrososphaera viennensis: a new species, genus, family, order and class of soil-dwelling archaea

Archaea-Post-ImageWhen a new species of microbe is discovered, it often fits into a known genus, forming a new outermost branch in the tree of life. Sometimes, though, organisms are discovered with DNA sufficiently different from all known species that they are placed into a new genus. Additions of new branches to the tree of life become rarer as we move closer to the ‘trunk’, towards ever broader classifications of organisms. Now, a team of Viennese researchers isolated a new species of archaea, named Nitrososphaera viennensis, which is the first known member of not just a new genus, family, or even order – it belongs to a whole new class of archaea. N. viennensis has been officially described in the International Journal of Systematic and Evolutionary Microbiology.

Archaea are considered ancient organisms but are still poorly understood life forms. They have characteristics in common with the two domains of life – bacteria and eukaryotes, the group that includes all other life forms. Like bacteria, archaea have no nucleus – but archaeal proteins are often much more similar to those of eukaryotes. After much debate throughout the 20th century as to whether archaea should be classified with bacteria or eukaryotes, they now form their very own domain in the tree of life.

Until recently, it was also thought that most archaea were extremophiles, thriving in environments with extremes of temperature, acidity, heavy metals, salinity, nuclear radiation, or availability of water or nutrients. It was only nine years ago that the first non-extremophilic, aerobic archaeon was cultivated from a marine sample. Similarly, N. viennensis was discovered in soil from the gardens of the Faculty of Ecology at the University of Vienna: a decidedly moderate environment. Continue reading

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New to Science – August Edition

200329304-001Each month, the Society for General Microbiology publishes the International Journal of Systematic and Evolutionary Microbiology, which details newly discovered species of bacteria, fungi and protists. Here are a few of the new species that have been discovered, and the places they’ve been found. The full papers are available to journal subscribers, but the abstracts are free to read.

The glorious weather here in the capital has seen London Zoo become a visitor magnet as city dwellers and tourists alike. In particular, the newborn black-capped squirrel monkey baby has been drawing squeals of delight from an adoring crowd.

Close cousins of this tiny new world monkey, a group of marmosets, has been found to be home to a new species of bacterium – Bifidobacterium aesculapii – which was discovered by Italian scientists in the faeces of a baby marmoset. Similarly, lion-tailed macaques in Fota Wildlife Park, Cork, Ireland, yielded Campylobacter corcagiensis upon investigation by researchers from Cork and Belgium.

In Prague, Czech scientists have painstakingly reared bumblebee queens in a laboratory. In their digestive tract, they discovered the new Lactobacillus bombi, a new member of a genus of bacteria that convert sugar to lactic acid. Working in the field, a team of Korean researchers isolated Flavobacterium faecale from the stool of penguins near King Sejong Base, King George Island, Antarctica, while another group isolated Litoreibacter ascidiaceicola from a golden sea squirt in the Sea of Japan. Continue reading

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Learning more about the Chikungunya virus

ResearchBlogging.org8013880499_c7ec99ee21_zChikungunya, an emerging viral infection carried by mosquitoes, has been making headlines across the US over the past few weeks. But what is Chikungunya? How does it spread? Jon Fuhrmann investigates.

The American Centre for Disease Control (CDC) first reported the existence of Chikungunya in the Caribbean as recently as December 2013. Since then, the number of infections in Americans returning from the Caribbean have steadily risen and have been confirmed in 35 states – a remarkable feat for a virus that, until less than a year ago, was undetected in the Western hemisphere. To make matters worse, two infected patients in Florida had not travelled at all: mosquitoes within the United States had transmitted the virus for the first time.

Chikungunya is transmitted by the tiger mosquito (Aedes albopictus) and the yellow fever mosquito (Aedes aegypti). Discovered in Tanzania in 1952, the virus’s name means “that which bends up” in the language of the Makonde people of Tanzania and Malawi. This is in reference to the extreme joint and muscle pain caused by the virus, which sees many patients writhing in agony. While Chikungunya infections are rarely fatal, chronic arthritis and long-term pain can persist for years after infection in older patients. Continue reading

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The Longitude Prize 2014 needs YOU

481459339The Longitude Prize 2014 was announced a few weeks ago to much media fanfare. After a vote, the British public decided that the prize should focus on the rise of antibiotic resistance. Joshua Ryan-Saha, Assistant Manager of the Longitude Prize, blogs here, asking members of the Society for General Microbiology to have their say on the design of the prize.

The growth of anti-microbial resistance will impact all of us. The World Health Organization estimates that antibiotic treatments add an average of 20 years to our lives. However, our overuse of antibiotics has allowed bacteria to evolve resistance, leading to the emergence of untreatable superbugs that threaten one of the cornerstones of modern medicine. How we respond to the growing global antimicrobial resistance is one of the most important science policy questions of our age.

The Longitude Prize 2014 will encourage the development of new point-of-care diagnostics that will help clinicians make better informed decisions when prescribing antibiotics, restricting their use only to those cases when they are beneficial. We know that diagnostics alone can’t solve the problem of anti-microbial resistance, but they are a central part of addressing the problem of antibiotic overuse. While the £10m prize fund is comparatively small when compared with the total global research spend in this area, a prize of this scale could make a tremendous difference in stimulating new and innovative diagnostic methods.

Over the last year, Nesta and our partners Science Practice have been working with a range of experts in this field to design a challenge prize that will encourage individuals and teams from across the world to try and solve it. In our paper for open review, we have outlined what we have come up with so far. We have tried to design this prize in a way that makes it potentially achievable within the five-year timescales, while ensuring it is challenging enough to encourage breakthrough innovations. We also hope that this challenge is accessible to a wide pool of potential competitors.

Microbiology is clearly a central aspect of antimicrobial resistance, and microbiologists will likely compete for the Longitude Prize 2014. As such, your input on the open review would be particularly valuable, both for Nesta and for members of the Society for General Microbiology. With the help of your thoughts and comments on the paper for open review we can formulate a truly effective prize.

What happens next?

Working with the Longitude Committee, we will use the responses to the open review to amend and adjust our challenge criteria. Subsequently, in October this year we will announce the full judging criteria and terms and conditions which will explain exactly what you need to do to win the prize.

At this point we will ‘fire the starter’s pistol’ for innovators and inventors from across the world to begin developing new point-of-care diagnostics that will help us preserve the efficacy of antibiotics for future generations by addressing the problem of antibiotic overuse and inappropriate use.

We believe that the Longitude Prize will be more robust and accountable after this process is complete, so please read our report and provide your feedback. The open review closes on 10 August.

Joshua Ryan-Saha

This blog was originally published by Nesta. You can read the original blog post here.

Image credit: Thinkstock
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