Antibiotics affect the mouth and gut differently

When we discuss antibiotic resistance, it’s not always clear where the resistance is developing or how exactly the resistance develops. A study out of the UK and Sweden looked at two niches, the gut and the mouth, to understand the difference between how the different parts of the body react to antibiotics.

The scientists discovered that these two parts of the body reacted and recovered very differently after a one-week course of antibiotics. They took fecal and saliva samples prior to the antibiotic regime and then gave the study participants a weeklong course of clindamycin, ciprofloxacin, minocycline, amoxicillin, or a placebo and continued taking fecal and saliva samples for a year.

They found that the oral microbiome recovered much faster than the gut microbiome back to its normal state. It took much longer for the gut microbiome to recover and for participants taking ciprofloxacin, diversity was changed even after 12 months. They also found that while participants largely had genes associated with antibiotic resistance in their gut prior to the trial, the amount of antibiotic resistant genes increased after taking the antibiotic. Antibiotic resistant genes in the mouth remained largely stable before and after treatment.  It was also observed that butyrate production, a health associated short-chain fatty acid, was severely affected by ciprofloxacin and clindamycin.

This raises a number of questions like why does the oral microbiome recover so much faster than the gut microbiome? And why isn’t there a similar increase in antibiotic resistant genes in the mouth like we see in the gut? While this study raises many questions, it provides an opportunity to look at the mouth and better understand what is unique about that environment in comparison to the gut. 

Antibiotic use in children may increase risk of obesity

We’ve talked extensively on the blog about antibiotics and the both positive and negative effects they can have on people’s health. Marty Blaser, professor at NYU School of Medicine and the world leader in studying antibiotics and their role on obesity and other health effects, published a study in Nature Communications last week on the effects that antibiotics can have if administered early in life.

Dr. Blaser and his colleagues used mice to administer various antibiotic regimes that included amoxicillin and macrolides. They provided the mice three antibiotic treatments, called pulsed antibiotic treatment (PAT), to the mice to mimic frequent antibiotic use in children. They found that the mice that were given the PAT saw short-term increases in weight as well as bone growth, specifically increased bone growth after amoxicillin treatment and increased fat after tylosin (macrolide) treatment.

The scientists also saw long-term alterations in the gut microbiota of mice given a PAT regime. Mice that were given antibiotics had decreased microbial diversity different proportions of bacteria compared to control mice. Surprisingly, the change in microbiome persisted until the time of the mouses' deaths, 120 days after the last antibiotic treatment. They also saw differing gene expression in the mice that were given pulsed antibiotic treatments. These two results give evidence that antibiotic use is leading to permanent physiological changes in the body. 

Dr. Blaser has long been telling us that the early stages of life, the time when we most frequently administer antibioitics, is critical to development and that antibiotic use can drastically alter this development. This study supports other research by Dr. Blaser and colleagues that has shown that antibiotic use in early life predisposes us to obesity.

While we know antibiotic use can have these negative long-term effects, they are still essential and are life-saving drugs for when we have bacterial infections. The authors state that this work and other work showing the negative effects antibiotics can have should lead to increased awareness as well as a re-examination of policies and guidelines to antibiotic use in humans.