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Thursday, 28 April 2011

MRSA - Supergerm immune to Kryptonite


More years ago than I care to remember, I saw a stand-up comedian doing a (what I thought at the time) very funny rant on the old marketing slogan for bleaches and detergents, “Kills 99% of all known germs – dead!”

The first question he asked was the obvious one about whether there were any other ways to kill something other than dead. He then went on to speculate about the other one per cent which weren’t killed. “There they are, sitting in your toilet, on your kitchen surfaces, in your kitchen sink. They’re lapping up the detergent and loving it! They’re shouting out for more and getting bigger and stronger all the time until, one day, they come bursting out on you, big and mean and ugly – Supergerm!”

The problem is, it’s not a joke – it has become a sad fact.

In the normal course of events, Staphylococcus aureus is a fairly benign bacterium which is carried by at least 20% to 30% of everyone on earth on their skin or, most commonly, in their noses. It lives a rather boring and benign life in its host, generally not causing any damage. In particular circumstances, however, especially in the case of people with compromised immune systems, it will infest open wounds and prevent them from healing and it can also cause blood poisoning (sepsis), toxic shock and a particularly nasty form of pneumonia. In other words, though it is usually fairly peaceful, when it really gets going it can kill.

When Alexander Fleming accidentally discovered penicillin in 1928, he was actually investigating the properties of various staphylococcus bacteria – what he found out was that a secretion produced by a mould of the Penicillium family killed staphylococci. The first antibiotic was developed and millions of lives have been saved as a result. Unfortunately, in the past few decades, many antibiotics seem to have been losing their efficacy. For this we have only ourselves to blame.

Charles Darwin described evolution as “the survival of the fittest” and, seen from one point of view, the history of species on our planet is one of intense competition with each other, even warfare. (There is, of course, much more to evolution than this simplification, but it does contain a lot of truth.) As Tennyson put it, “Nature, red in tooth and claw.” Once humanity discovered that bacteria were behind many of the illnesses which kill so many millions of people every year, we declared war on them. To continue using the imagery of conflict, the development of penicillin – and antibiotics in general – provided us with a marvellously effective weapon to take the war to the enemy.

Any general worth his salt will tell you that there is really only one way to definitively win a war; you kill all the enemy soldiers or force their surrender. As long as units of the foe continue to survive and fight you, the war isn’t over. Worse, if those surviving enemy units develop tactics and weapons to counter you in the areas in which you are tactically and technologically superior, then you have a real problem. This is what has happened in the “war on germs.”

In the past few decades, there have been more and more incidences of bacteria developing which have become resistant to the most common antibiotics. To understand how this has happened, we have to look at the way antibiotics work and then just apply evolutionary logic – and penicillin is a very good example.

Penicillin destroys bacteria by damaging the cell walls of bacteria. Bacteria are one-celled organisms – basically just a mass of liquid held together by a more solid envelope, the cell wall. Penicillin attacks a particular building block of this wall so that when the bacteria wants to divide (which is the way bacteria reproduce) and thus stretches its envelope, making it thinner in the process, it rips and the creature, put simply, bursts.

But some bacteria are stronger than others, more thick-skinned, if you will – so it takes continued application of the antibiotic to kill them all. If the course of antibiotics isn’t given for long enough or in a sufficiently strong dosage, all that happens is that all the thinner-skinned bacteria are killed; those with thicker skins survive – and they’re the ones who reproduce. So the antibiotic treatment itself forces a kind of natural selection among the bacteria, until – if this process is repeated long and often enough – you get a strain of bacteria which isn’t much bothered by antibiotics. And this strain doesn’t even have to worry about competition from other relatives, since the nice humans have obligingly killed them off.

Over the course of decades, the irresponsible use of antibiotics has forced the evolutionary development of strains of bacteria which are immune to them. This has happened in four basic ways. Firstly, the overprescribing of antibiotics generally, frequently for illnesses which are not helped by them (antibiotics are useless for viral infections like the ‘flu and the common cold) or with which the normal immune systems of the patients could have easily dealt on their own.

Secondly, the frequent failure of patients to follow the instructions for taking the medicine (“after two days the symptoms cleared up and I didn’t like the side-effects so I didn’t take it any more”), leading to many situations where a residue of stronger bacteria survives the treatment.

Thirdly, insufficient attention to hygiene in hospitals. Bacteria love hospitals; they’re full of potential hosts with weakened immune systems, lots of opportunities to gain access to them through wounds etc. and lots of friendly doctors and nurses on which to hitch free rides from one patient to another. And, of course, lots of training for dealing with antibiotics. Hospitals can be tough for bacteria at first but once they’ve learned to deal with the antibiotics they’re germ heaven.

And fourthly, the unbelievable irresponsibility with which the agricultural business has used antibiotics. Animals, kept at closer quarters and in larger numbers together than nature ever intended, are routinely given low-level antibiotics from the cradle to the slaughterhouse, just to make sure they don’t get sick. As a result, minimal levels of antibiotics are passed into the human food-chain and even into our drinking water supplies. More training for the germs.

Staphylococcus aureus
So, let us now return to our friend, the Staphylococcus aureus. Over the course of time, many strains of this particular little beast have developed a first-class resistance to all sorts of antibiotics of the penicillin family and have been given the general name “Methicillin-resistant Staphylococcus aureus (called after a particular penicillin derivative), more commonly (like J.R. Ewing) known by its initials, MRSA.

The number of people killed by MRSA every year is something very difficult to ascertain; one of the numerous cases of lies, damned lies and statistics in public health. A basic problem is that many of those at risk (children, chronically ill, elderly people, etc.) may be significantly weakened by an MRSA infection before finally dying of something else. One study suggests that around 19,000 people died of MRSA-related causes in the USA in 2005. A German TV report claimed that 160,000 people contracted an MRSA infection in German hospitals in 2008 and the German Society for Hospital Hygiene estimated that 40,000 people in Germany died in 2009 as a result of it.

Once someone has contracted an MRSA infection it is very difficult to get rid of it, particularly if they have a weakened immune system. Depending on the strain involved, certain special (very expensive) antibiotics may be effective, but frequently in the everyday clinical world, the precise strain is never analysed and no specific treatment is followed through. All too often, this is – as in so many things – a question of short-term costs. (That subsequent longer term costs of treating people with a chronic MRSA infection are usually much higher is something which the pencil-pushers running the various public and private health insurance corporations world-wide don't seem to want to think about.) Otherwise, the only thing to do is to isolate the patient, do everything possible to strengthen his/her immune system, try all kinds of alternative stuff which have been reported to sometimes work, like inhalations with lavender or tea-tree oil and … wait.

For the past ten years, I have worked a lot with people who are on respirators. They generally have tracheotomy tubes and these surgical holes cut in their windpipes are magnets for MRSA. Given their precarious state of health, they are regularly in and out of hospitals and many of them pick up a multi-resistant bug sooner or later. For them, the isolation is the worst – if you really want to deal with the infection and ensure that it doesn’t spread then you have to confine them to their rooms and make sure that everyone who visits them wears gloves, facemask and disposable surgical gown. For people punished enough by the vagaries of fate, this extra isolation can be very hard to bear.

What makes me so angry about it is that it could all have been avoided. Instead, we have taken the wonderful new weapon which was antibiotics and, in the past sixty or so years, proceeded to systematically blunt it.

MRSA is only the beginning. In recent years, there are increasing reports of strains of the bacteria responsible for tuberculosis and pneumonia (among others) emerging which are immune to the standard antibiotics used to treat them up to now. Supergerm is not alone, he’s called all his cousins and friends and they’re coming to the party too. The problem is that kryptonite doesn’t work on them any more.

 

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