New research has publicised the threat from ‘Steno’ – a hospital-acquired infection which in some strains, is resistant to all available antibiotics.

Researchers from the Wellcome Trust’s Sanger Institute and the University of Bristol have been mapping the geonome sequence of Stenotrophomonas maltophilia, known as Steno.

Dr Matthew Avison from the University of Bristol 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.” The map of Steno's genome is published today in the Genome Biology journal.

The UK saw 1,000 cases of Steno blood poisoning in 2007. Of these, nearly 300 were fatal. Steno is difficult to remove by normal cleaning and flourishes in moist environments, such as taps and shower heads.
A typical infection would be caused via catheters left in place for long periods of time. 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.

The major risk to hospital patients is when the microbe grows as a ‘biofilm’ coating on catheters and ventilation tubes, from where it can enter the bloodstream or lungs. Steno infections can cause blood poisoning (septicaemia) or pneumonia.

The most at-risk groups are immunocompromised patients, such as those undergoing chemotherapy, adults with cystic fibrosis and older people in intensive care.

Not spread like MRSA
The agency responsible for monitoring infections diseases, the Health Protection Agency points out that Steno causes less than 1% of hospital acquired infections. An HPA spokeswoman added that it usually only affected patients who were already "very sick" and never infected healthy people, stating: "The infection does not spread in the manner of MRSA or Clostridium difficile (the major HAIs). Until recently it had not shown much of a trend that it was becoming more resistant, with the antibiotic co-trimoxazole effective against virtually all strains.”

The latest HPA figures found 773 cases of blood poisoning caused by Steno infections in 2006 (a rise of 160 since 2002). There is little spread between patients, and infections are mostly caused by one-off strains. Usually if more than one person on a ward is infected it will not be by the same strain."

Steno is not transferred between patients as a result of poor hospital cleaning or staff hand hygiene, as can often be the case of MRSA and Clostridium difficile.

Dr Lisa Crossman, of the Wellcome Trust's Sanger Institute in Hinxton, Cambridgeshire, said that decoding the infection's genome should help combat Steno's ability to stick to surfaces like catheters and ventilators, form biofilms, and fight its drug resistance: "If we know which proteins cause 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."