Identifying superbug strains

The UK Health Protection Agency has developed a quick and accurate method of identifying strains of the ‘superbug’ Acinetobacter baumannii.

A type of bacterium widely found on our skin and in the environment, A. baumannii has now become a major threat in hospitals where it can cause serious infections, such as pneumonia in severely ill patients.

Like the well known bacterium MRSA (methicillin-resistant Staphylococcus aureus) the new types of A. baumannii are resistant to nearly all antibiotics, so doctors have very few treatments available.

Three resistant strains of the bacteria are currently circulating in the UK, while Australian hospitals are reporting cases as well.

A molecular method has been successfully implemented by medical researchers at the Royal Free Hospital, as a quick and accurate means of identifying which strain of the bacterium is present. The method was discussed at the Federation of Infection Societies Conference 2007 held at the University of Cardiff, UK, in late November.

“Some of these new strains of A. baumannii, known as epidemic clones, can spread rapidly and widely between patients and have the potential to cause outbreaks,” said Kerry Williams of the Royal Free Hospital, UK.

“We currently encounter two of them at our hospital, so we need a reliable and rapid means of identifying and discriminating between the different clones.”

The drug-resistant strains of the bacteria are particularly dangerous in intensive care units where they can cause pneumonia, infect wounds, or cause urinary-tract infections.

“Like MRSA, A. baumannii can be found on the skin without actually causing an infection — this is known as colonisation. The new test is important because it means we can rapidly identify patients who are colonised with drug-resistant strains of the bacteria so that special infection-control measures can be put in place,” said Williams.

“This reduces the risk of transmission to other patients and the possibility of an outbreak occurring. The ability to distinguish between the clones circulating is also important because it allows us to monitor transmission in our hospital.” The new test, called multiplex-PCR, is based on identifying unique gene sequences in the bacteria and has the potential to be developed as a rapid screening tool for intensive care units dealing with the disease. It could lead to better patient management, with faster, more appropriate treatments for individuals, prompt control of infections and lowered transmission rates to other patients.