What makes a bug super? Part II

By Siouxsie Wiles 07/03/2011

In a recent post about the ‘superbug’ Staphylococcus aureus, I mentioned reading an article in the weekend Herald about a guy who had

suffered badly from a series of major infections, including an ESBL superbug bacterium

So what is this ESBL superbug? ESBL stands for Extended Spectrum Beta Lactamases, a group of enzymes that are able to  deactivate a class of antibiotics known as cephalosporins. From this you can see that ESBLs aren’t really superbugs but rather a means to make a bug super. There are now a large number of different ESBLs, the genes for which can frequently be found on plasmids, making them very easy for bacteria to share.

ESBLs can often be found in isolates of Escherichia coli and Klebsiella pneumoniae. Infected people can either be completely oblivious to their presence, displaying no symptoms (while probably spreading the bugs around…) or they can end up with high fevers, pneumonia, abdominal or urinary tract infections. In extreme cases, the infection can be fatal.

At a recent symposium on superbugs held by the Maurice Wilkins Centre for Molecular Biodiscovery, we were told that North Shore Hospital has suffered from an outbreak of ESBL+K. pneumoniae since July 2007 and ESBL+E. coli since late 2008. They began to take routine rectal swabs from patients to identify colonisers coming into hospital and identified 4000 of them by late 2010. Interestingly, they found that of those patients who tested negative for an ESBL bug, roughly 1 in 1000 patients went on to develop a blood infection. In contrast, roughly 85 in 1000 patients developed a blood infection if they tested positive.

While it is clear ESBL+ bacteria can be caught in the hospital, it is also obvious that many people who go into hospital are already carrying their own superbug without even knowing it.

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