Business Weekly - Cambridge, UK

Multicoloured boxes in outer ring are genes; the red boxes are regions transferred from other organisms - these are significant

Steno, as the bug is known, is able to rapidly develop a resistance to drugs, according to Sanger research. Stenotrophomonas maltophilia causes around 1,000 reported cases of blood poisoning in the UK each year and a third of these are fatal.

Researchers say that Steno spreads through wet areas such as taps and shower heads and can cling to equipment such as ventilator tubes and catheters, growing into a biofilm coating that is tough to remove.

Once in the bloodstream it can cause septicaemia in patients whose immune system has already been weakened. The organism is also found in the lungs of many adults with cystic fibrosis, and causes ventilator-associated pneumonias, particularly in elderly intensive-care patients.

A paper to be published by Sanger and the university in Genome Biology will demonstrate how understanding the genome of Steno will enable researchers to discover how to deal with this particularly resistant organism.

Dr Matthew Avison from the University of Bristol, and senior author on the paper said: "This is the latest in an ever-increasing list of antibiotic-resistant hospital superbugs. The degree of resistance it shows is very worrying.

“Strains are now emerging that are resistant to all available antibiotics, and no new drugs capable of combating these 'pan-resistant' strains are currently in development."

Pan-resistant Steno infections could even be as hard to treat as MRSA and C. difficile (known as Cdiff) infections. Although Steno is common in the environment, infections are rarer than those of MRSA and Cdiff and are exclusively hospital-acquired.

Steno flourishes in moist environments, such as around taps and shower heads, and so can be easily transferred to patients. A typical route of entry for this superbug is through catheters that are left in place for long periods of time. These long-dwelling catheters are used most often for seriously ill patients and some undergoing chemotherapy.

Steno can stick to the catheter and grow into a 'biofilm'. When the catheter is next flushed, the Steno biofilm enters the patient's bloodstream. If their immune system is impaired (which is often the case in the seriously ill and those undergoing chemotherapy) the organism can multiply and cause septicaemia.

The gravity of this situation is highlighted by the results from the team since, as this new research shows, these septicaemic patients will often be treated with antibiotics to which Steno is largely resistant.

Scientists say the key questions that need to be addressed are: How does Steno stick to surfaces like catheters and ventilator tubes? How does it form biofilms that make it resistant to our attempts to decontaminate and clean these devices? Why is it resistant to antibiotics?

Dr Lisa Crossman from the Sanger Institute and first author on the paper explained how the research might address these questions: "The genome sequence should help us to combat these properties. For example, if we know which proteins allow it to stick to surfaces, we could try to develop biochemical compounds that interfere with this interaction. If we understand its antibiotic resistance mechanisms, we might be able to design inhibitors that block them."

While, fortunately, Steno infections are still relatively uncommon, they are on the increase. Furthermore, there are two other organisms that, like Steno, cause infections by colonising catheters and so on, but are more common.

Dr Avison added: "Genome sequences for these two also exist, and so now we can look at what they all have in common genetically that might explain why they all behave in a similar way in the hospital."

TrackBack URI for this entry

Comments (0)

Subscribe to this comment's feed