Short-term antibiotics can raise bacterial load and pathogenic potential in intestinal microbiota

   According to a murine study presented at DDW 2013, held in May 2013 in Orlando, short-term antibiotic treatment by unabsorbed antibiotics induced a clear disruption of the normal flora adherent to the intestinal mucosa, resulting in a significantly higher bacterial load and the presence of bacteria with a high pathogenic potential.

   Researchers from the University Lille Nord de France, Lille, France, and colleagues compared the level and types of bacteria present in the lumen, near and inside the epithelial cells (adherent flora), in the colon, ileum and jejunum of healthy mice and at different times after a three-day antibiotic treatment. They investigated the luminal and adherent microflora in colon, ileum, and jejunum biopsies from three groups of 10 C57BL/6 mice treated with three days' oral administration of vancomycin (40mg/kg/day) and gentamicin (3mg/kg/day) and one control group without antibiotherapy.


   They observed no significant quantitative changes of the luminal microflora in any part of the investigated digestive tract, but adherent microflora was significantly increased in comparison with the untreated group. This occurred after only three days of antibiotic treatment, especially in the colon (4+/-0.4 logCFU/g of colon in control mice vs 5.8+/-0.5 three days after antibiotic treatment, P=0.01). 

   The increase persisted three and seven days after cessation of antibiotic therapy (6.7 +/- 0.4 logCFU/g of colon, P=0.001 and 5.4+/-0.4 P=0.03, respectively, three and seven days after antibiotic treatment). The modification of the adherent flora was due to a significant increase of enterobacteria and enterococci. 

   “Those results illustrate the importance of interbacterial interactions in the control of the normal flora and its diminution when approaching the epithelial cell layer,” the French investigators concluded.