Antibiotic Resistance and Irresponsibility

There's a very interesting article in Emerging Infectious Diseases about which risk factors are likely to result in an increased likelihood of a macrolide (a class of antibiotics) resistant Streptococcus pneumonial infection. One important factor: having failed to take a full course of antibiotic therapy in the previous six months. In other words, patients didn't listen to their doctor. Usually, the arguments for responsible use of antibiotics revolve around not making a general problem worse for others. Here we have pretty compelling evidence that if you're stupid and don't do what your doctor tells you to do, you will be worse off. So don't screw around: always follow your doctor's instructions when you're prescribed antibiotics (of course, if you develop adverse reactions, call your doctor immediately--you could be having an allergic reaction or be susceptible to side effects, and a switch to another antibiotic might be indicated). More details about the article itself below.

It's a pretty good article, although one problem is that several different classes of factors are analyzed separately, making it difficult to clearly discern the exact cause (or actually, the appropriate correlation--yes, correlation does not equal causality. You get a gold star). For example, blacks are less likely to contract macrolide resistant infections than whites. Is this result from the inherent burdens of honkytude, from the lack of access blacks have to healthcare--making it less likely they would receive an antibiotic at all (you can't misuse an antibiotic you don't have), or from something else? Also, these data were collected from Southeast PA, so they might not be applicable to the rest of the country.

Despite that caveat, there are some very startling conclusions from this paper:

1. Since I brought up ethnicity, it seems to have a significant effect. Whites were 1.8 times more likely to have an erythromycin resistant infection than non-whites (excluding Latinos from non-whites), while Latinos were 3.1 times more likely to have an erythromycin resistant infection than non-whites. No idea why this would be the case.
2. Living in a nursing home did not affect macrolide resistance. Nursing homes often have high frequencies of resistant infections, such as MRSA[link], so this was surprising.
3. A history of stroke significantly lowered the probability of a resistant infection by 80%. Gotta get your stroke on?
4. Influenza vaccination was also important, and doubled the likelihood that one would have a macrolide resistant infection. This isn't particularly surprising, since those with a previous history of pneumonia are considered 'at risk' for influenza and would likely receive the vaccine.
5. While macrolide use in the previous six months increased the odds of a macrolide resistant infection by 2.8, quinolone use (e.g., ciprofloxacin, also known as 'Cipro') did not increase the chance of a macrolide resistant infection. This is encouraging, because there does not appear to be correlated selection between these two classes of drugs. Thus, the probability that if one drug doesn't work, the other one won't either is very low. (an aside: this is where the way the data are reported is frustrating. If you actually look at the article, when a univariable analysis is performed, quinolone use did have an effect, but in a multivariable analysis, it doesn't. Why, then, would you report the univariable analyses, since they don't seem pertinent? Very frustrating).

Anyway, if you're inclined to read these sorts of articles, I recommend it.