Antibacterial drugs and the risk of community-associated methicillin-resistant Staphylococcus aureus in children. Schneider-Lindner, et.al., Arch Pedicatr Adolesc Med, 2011 Dec:165(12):1107-14.

This is a great study done in England, where a database of medical treatment for the whole country is available for research (unlike in the US).  These researchers asked the question, “If you are prescribed an antibiotic, does that increase your risk of subsequently contracting a MRSA infection?”  So the researchers reviewed records for children between 1994 and 2007, including ~300 MRSA cases and >9000 controls.

Not surprisingly, they found that a child who is prescribed an antibiotic does, in fact, have an increased risk of a subsequent MRSA infection.  The surprising thing is how much of an increased risk this represents.

If you receive one antibiotic prescription, your risk of MRSA infection within the next 6 months more than doubles. If you receive two antibiotic prescriptions within 150 days, your risk of MRSA more than triples.  Then the risk really goes up.  If your receive three antibiotic prescriptions within 150 days, your risk of subsequent MRSA infection goes up eleven fold.  Four antibiotic prescriptions and your risk for MRSA rises more than 18 fold.

Quinalones are particularly prone to increase the risk of subsequent MRSA infections.

These researchers had previously studied adults and found the same thing.  (Antimicrobial drugs and community-acquired methicillin-resistant Staphylococcus aureus, United Kingdom).

I’m going to prevent weeds by killing the grass.

This, of course, makes sense.  A great analogy that I like to use with inmates who want an antibiotic prescription for their viral syndrome is of a lawn of grass.  The grass itself prevents noxious weeds, like thistle, from sprouting.  The grass chokes them out.  But if I were to kill the grass by spraying Roundup, what are the odds that thistle will grow now?  The grass is like our normal, healthy colonies of bacteria.  They help us in many ways, including “choking out” noxious bacteria like MRSA. There has been some great recent research into the beneficial effects of our personal bacterial colonies, such as this report on the  Human Biome Project.

Using antibiotics is very like using grass killer.  Antibiotics are a great medical tool when used properly, but they also have the potential to cause great harm.  If you prescribe an antibiotic for a viral syndrome, like a typical case of sore throat or bronchitis, your potential for benefit is zero.  It’s a virus!  But your potential for harm is the same as it always is.  This study shows that one unnecessary prescription doubles your patient’s subsequent risk of MRSA.  If you prescribe Augmentin, the risk of diarrhea is one in six!  So you cannot help this patient with a virus by prescribing an antibiotic; you can only harm them.

The CDC has published excellent guidelines on the proper use of antibiotics for sore throats, bronchitis and sinusitis.  I have written about these guidelines previously here (Evidence-Based Use of Antibiotics Can Save Your Jail Money! and here (Don’t Use Antibiotics for Most Cases of Pharyngitis!, although my focus then was how inappropriate antibiotic prescribing wastes money.

The more important message is that inappropriate antibiotic prescribing harms your patients.  According to these studies, if you reduce your antibiotic prescribing by following these guidelines, you may find that your MRSA infection rate goes down, too! Bonus!