The killer bug that lurks unseen in the tap water
The organism which caused the RVH outbreak exists harmlessly in 10% of adults. But in premature babies it can be deadly, says Sir Hugh Pennington
Published 26/01/2012 | 08:00
Pseudomonas thrives in wet, warm and aerated conditions. So the news that sink taps were the source of the organism that caused the deaths of three babies at the Royal Jubilee Maternity Hospital's neo-natal unit came as no big surprise.
It appears that taps were the source at Londonderry's Altnagelvin Hospital where one baby died in December 2011. Replacing the taps will remove the source of the organism and make the units safe.
Pseudomonas is very common in the environment. It can live in our intestines as well. Up to 10% of us carry it there harmlessly.
It produces a variety of toxins that can damage the function of cells and destroy tissues. But our immune systems cope with it well.
The worst it can do is usually limited to chronic, but not life-threatening, infections, although eye infections from industrial injuries, or contaminated contact lenses, can be very serious.
The pseudomonas ear infections that commonly affected North Sea oil-rig divers who spent weeks in humid chambers under high pressure between dives to avoid decompression ('the bends'), were only important because of the pain.
Another of its specialities - 'jacuzzi rash' (warm moisture again) - is no more significant than a minor irritation of skin follicles.
But patients with severe burns, those in intensive care on artificial ventilation, those being treated with immunosuppressant drugs, those with diseases that cause immunosuppression - like leukaemia - and people with cystic fibrosis are particular targets for lethal infections, because defences are down.
It is the same for premature babies. Their immunity is not developed enough to stop the bacterium spreading through the body.
So the prevention of pseudomonas infection in these special groups and under these special circumstances is paramount. Two other factors add to the importance of this. Not only does it resist some disinfectants and antiseptics, it can grow in them as well, even at room temperature.
And it is naturally resistant to many of the commonly-used antibiotics, although, fortunately, there are quite a few that are effective.
In patients with cystic fibrosis, the organism shows other teeth as well. It produces a mucoid substance which forms a film in the lungs.
At the same time, it produces molecules which signal the bacteria to form a closely-linked community. It might have been doing this in the neo-natal unit taps.
A crucial tool in working out what is happening in an outbreak is bacterial fingerprinting.
The most sensitive methods compare the bacterial DNA. Not only is this approach vital in tracking down the source of the cause of an outbreak, quite often it provides the first evidence that an outbreak is in progress - that two or more infections are being caused by an identical organism, and that the bacteria are coming from a common source.
This is what has happened, and what has been done, in this outbreak. I must say that the speed of the detective work and its results does not surprise me.
My opinion is that Northern Ireland is fortunate to have such excellent microbiological laboratories and public health services.
More work still needs to be done. Some babies still have pseudomonas on their skin (but are not infected), while another baby is infected.
But the neo-natal service and network is working well.
This is a characteristic of this part of the health service - it works wonders. It is at the cutting-edge of modern medicine.