How Super are Superbugs?

2 02 2010

Unless you have been locked in a darkened room for the past decade you’re sure to have heard of the dreaded superbug MRSA.   But what is it, what can it do to us, and is it really very super?

First things first, what is MRSA?  Those four ominous initials stand for Methicillin Resistant Staphylococcus Aureus.  It is a type of bacterium, with the scientific name Staphylococcus aureus, that causes a whole host of life threatening diseases but can’t be killed off by the antibiotic methicillin.  Or, it has to be said, by pretty much any of the antibiotics we throw at it.

And what can it do to us if we catch it?  You may simply have a superficial infection of the skin or the soft tissue beneath it, perhaps a boil or impetigo, and make a full recovery.  However, in some cases bacteria spread into your bloodstream and to other organs in the body.

The list of ensuing diseases does not make for very pleasant reading:

  • Septicemia – blood poisoning
  • Endocarditis – infection of the heart valves
  • Necrotising pneumonia – infection of lung tissue
  • Toxic Shock Syndrome – bacteria can release a potent toxin into the body and cause fever, sickness and organ failure

Tragically, many people will know a friend or relative who caught MRSA during a hospital stay as the bug infects around 2% of all patients.  But where does it come from in the first place?  And how has it become an antibiotic resistant superbug?

A body full of bacteria

It may not be a very nice thought (my apologies to anyone reading whilst eating their breakfast), but the human body is covered inside and out with millions of microscopic bugs.  This includes things like bacteria, viruses and fungi.  Amazingly, there are actually 10 times more bacterial cells in your body than human cells.  They live on your skin, up your nose, in your mouth, throughout your gut, and most of the time they are completely harmless.  In fact, we could not survive without them.

Among these millions of germs is one particular type of bacteria called – you guessed it – Staphylococcus aureus.  It makes its home on the skin and inside the noses of 20% of people, but most of them will never know.  In a few people, however, the bacteria find a way to get inside the body.  This might be via a cut such as a surgical wound, or where a medical device is inserted – perhaps a drip or catheter.  When this happens it is bad news; devastating news if there are no antibiotics around to combat the infection.

DNA: the key to antibiotic resistance

One of the amazing things about bacteria is how they get their DNA.  Whereas we, like other animals, inherit all of our genes from our parents, bacteria can also pass useful segments of DNA from one to another, even to bugs of a different species.

Scientists discovered one such segment, called a cassette, containing several very important genes that protect the bug from antibiotics.  If you are a bacterium and a neighbour sends over the cassette, you can incorporate it into your genome and – voila – you are resistant.  You are now a superbug.

How super is MRSA?

Humans and bacteria seem to be locked in an arms race. As fast as we can develop new treatments or prevention measures, the bugs find a way to get round them and keep infecting us.  But as long as scientists keep up the research into new treatments, and continue to unravel the story of how the bugs are doing such a good job of making us ill, there is certainly hope.  MRSA may be super at getting round our defences, but we are fighting back with the product of our human brain cells.

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