Contrary to popular thinking, using antibiotics for a prolonged period may not lead to drug-resistant strains of bacteria in all cases. Much concern has been raised over the fact that overuse of antibiotics seems to be linked to more strains of drug-resistant bacteria like MRSA, methicillin-resistant Staphylococcus aureus.

The study seems to throw a kink into the current understanding of bacterial resistance. However, there are some limitations…

This variety of S. aureus or "staph" bacteria has plagued hospitals around the country, and can be fatal under certain conditions. While MRSA used to be sensitive to a variety of antibiotics, it is now very hard to kill the bug. But a new study shows that people taking antibiotics to treat acne do not seem to have greater likelihood for having a drug-resistant form of S. aureus than others.

In the study, the researchers studied 83 patients who had acne, some of whom were on antibiotic treatment and others of whom were not. The researchers wanted to compare how likely the antibiotic users and non-users were to have S. aureus living in their noses and throats. In the general population, anywhere from 40-50% of people are "colonized" by S. aureus, though it does not generally pose a problem.

Of the 83 participants in the study, 36 had S. aureus in their noses and/or throats; 2 of these people had MRSA. But in the long term (more than 2 months of use), antibiotic users were actually 70% less likely to have colonization than nonusers. Among antibiotic users, there was a greater likelihood of S. aureus colonization after the 2-month mark than before it (meaning that odds of colonization may increase somewhat over time), but this change was not significant.

Importantly, the use of antibiotics over the long term did not seem to be linked to a greater chance of having antibiotic-resistant strains of S. aureus. Some strains of the bacteria were resistant to certain antibiotics, mainly clindamycin and erythromycin, but there was no difference between antibiotic users and nonusers in this regard. Only about 10% of the bacteria tested were resistant to tetracycline, which is the most commonly prescribed antibiotic for acne.

The study seems to throw a kink into the current understanding of bacterial resistance. However, there are some limitations to the study, the obvious one being that only acne patients were considered. Therefore, the results might not be applicable to the general population. Also, only samples from the nose and throat were used, so it is possible that differences in colonization rates might be seen in other parts of the body. More research will need to look into how bacteria acquire resistance, since MRSA and other drug-resistant strains pose a serious threat to the population.

The research was conducted by a team at the University of Pennsylvania, and published in the April 11, 2011 online issue of Archives of Dermatology.