What is the CPE superbug that is present in Irish hospitals?

Dr Muiris Houston: CPE is the latest bug that is hard to kill with antibiotics

With the number of CPE cases in Ireland almost doubling in 2016, it is the most serious superbug challenge we face. Photograph: Getty Images.

Carbapenase-producing enterobacteriaceae (CPE) are the newest in a long line of superbugs that are hard to kill with antibiotics. A particular problem in hospitals, the bug was declared a public health emergency last October and has been the target of an intense campaign to control it since.

Last week brought news that hospitals are to contact some 5,000 people who may have been exposed to CPE while they were inpatients. While there is no immediate risk to these people, an expert group has decided they should be informed of the potential exposure.

Why weren’t patients informed while they were still in hospital? A patient is designated as a CPE contact by the infection control team in a hospital when it is judged that the patient has had significant specific exposure to another person carrying the superbug. Typically, this occurs when they shared a room or toilet facilities with a CPE patient.

But the contact may have been discharged before the laboratory test confirming their former room-mate has the bug becomes available. Hence the need for a catch-up process to ensure the 5,000 people are fully informed of their CPE contact status.


Carbapenase-producing Enterobacteriaceae is quite a mouthful. A carbapenemase is an enzyme that destroys meropenem and other antibiotics in the carbapenem group of drugs. Enterobacteriaceae are a family of bugs that live in the gut. E. coli is a well known example, but there are many others.

CPE lives harmlessly in the gut but can be dangerous if it gets into the bloodstream; more than half of all patients who develop bloodstream infections with CPE die as a result. Infection with CPE poses a particular risk to older people and those with reduced immune system function.

The bugs are shed in faeces and transmitted by direct and indirect contact with an infected person; a period of four weeks or more may elapse between that contact and the time at which CPE becomes detectable in the the next victim. CPE in the gut does not cause symptoms such as vomiting or diarrhoea.

CPE contacts do not need any treatment and do not need any testing for the bug. However, the HSE has said that if any CPE contacts want to be tested now that will be arranged by the hospital they were admitted to. And CPE contacts who are readmitted to hospital in future will need tests for CPE to be carried out at that time.

Statistically, people who are in contact with CPE have about a 1 in 20 chance of carrying the superbug. Those who carry CPE in turn have about a 1 in 20 chance of developing a CPE infection. So the the risk of a serious CPE infection in a CPE contact is in the region of 1 in 400.

There have been significant outbreaks of CPE infection in at least eight healthcare facilities in the Republic, resulting in prolonged bed closures and significant morbidity and mortality. Because of antibiotic resistance, there are very few therapeutic options with which to treat infected patients.

Of all the superbugs, CPE is the most difficult to kill with antibiotics. For over 30 years we have counted on meropenem to treat people who were seriously ill with Enterobacteriaceae infection. But CPE means that we cannot rely on meropenem any more and so doctors may have no safe, easy to use antibiotic to treat infection caused by CPE.

CPE is the latest threat to emerge as a result of AMR, with the number of CPE cases in Ireland almost doubling in 2016. CPE is the most serious superbug challenge we face. The emergency task force is working to maximise all available interventions to protect patients and it will hopefully succeed in preventing widespread hospital ward closures as a result of CPE.