Recent studies have shown that gut microbiota play a role in the pathogenesis of certain metabolic disorders such as obesity, insulin resistance, and type 2 diabetes. With these metabolic disorders becoming more prevalent, researchers aimed to examine whether antibiotics, drugs that alter gut microbiota, increase the risk of diabetes development. The findings of this study were published online on the European Journal of Endocrinology website. 

Using a large population-based database from the U.K., researchers  conducted a nested case-control study where cases were defined as patients with incident diagnosis of diabetes; the study included 208,002 diabetes cases and 815,576 matched controls (matched by practice site and duration and calendar period of follow-up). Antibiotic exposure greater than one year before diabetes diagnosis to one of the seven commonly used antibiotics in outpatient settings (penicllins, cephalosporins, quinolones, tetracyclines, macrolides, sulfonamides, and imidazole) was the primary exposure of interest.

While exposure to only one antibiotic prescription was not associated with increased diabetes risk, the risk did increase when patients were treated with 2–5 antibiotic courses, specifically with penicillin (adjusted odds ratio [OR]: 1.08), cephalosporins (OR: 1.11), quinolones (OR: 1.15) and macrolides (OR: 1.11). Diabetes risk also increased with the number of antibiotic courses with >5 courses of quinolones reaching an OR of 1.37. For TMP/SMX there was a modest increase in risk with 2–5 courses (OR: 1.1), while >5 courses of tetracyclines demonstrated an elevated risk (OR: 1.21). No association was seen between diabetes risk and imidazole, anti-fungal or anti-viral exposure. Adjustments were made for BMI, smoking, last glucose measurement and number of infections before the date of diagnosis. Adjusted analysis showed no change in risk for patients with type 1 diabetes.

The authors conclude that despite the possibility of unmeasured confounding, the findings of this study are consistent with previous studies which showed altered microbiota in patients with type 2 diabetes and increased obesity in those exposed to antibiotics during the first year of life. More research will need to be conducted to see how repeated courses of antibiotics change microbiota and perhaps whether antibiotics might improve glycemic control in patients with diabetes.