Abstract
The objective of this study was to assess the possible modifications due to amoxicillin-clavulanic acid (AMC) treatment on total bacteria and on Bifidobacterium species balance in human colonic microbiota. Eighteen healthy volunteers (19 to 36 years old) were given a 875/125 mg dose of AMC twice a day for 5 days. Fecal samples were obtained before and after antibiotic exposure. After total DNA extraction, total bacteria and bifidobacteria were specifically quantified using real-time PCR. Dominant species were monitored over time using bacterial and bifidobacterial Temporal Temperature Gradient gel Electrophoresis (TTGE). At the end of AMC exposure, total bacterial concentrations as well as bifidobacteria concentrations were significantly reduced compared to before AMC exposure:10.7±0.1 log10 16S rRNA gene copies/g vs 11.1±0.1 log10 (p = 0.003) and 8.1±0.5 log10 16S rRNA gene copies/g vs 9.4±0.3 log10 (p = 0.003), respectively. At the same time, the mean similarity percentages of TTGE bacteria and TTGE bifidobacteria profiles were significantly reduced compared to before AMC exposure: 51.6%±3.5% vs 81.4%±2.1% and 55.8%±7.6% vs 84.5%±4.1%, respectively. Occurrence of B. adolescentis, B. bifidum and B. pseudocatenulatum/B. catenulatum species significantly decreased. Occurrence of B. longum remained stable. Moreover, the number of distinct Bifidobacterium species per sample significantly decreased (1.5±0.3 vs 2.3±0.3; p = 0.01). Two months after AMC exposure, the mean similarity percentage of TTGE profiles was 55.6% for bacteria and 62.3% for bifidobacteria. These results clearly demonstrated that a common antibiotic treatment may qualitatively alter the colonic microbiota. Such modifications may have potential long-term physiological consequences.
Highlights
The human colonic microbiota forms a complex ecosystem which plays important roles in human health and disease, with regard to nutrition, pathogenesis and immune function of the host [1]
We explored, on a 76-day period, the quantitative and qualitative changes occurring in total microbiota and in the Bifidobacterium genus, in 18 adult men after a 5-day amoxicillin-clavulanic acid (AMC) treatment, using specific real-time PCR and PCR-Temperature Gradient gel Electrophoresis (TTGE) combined with cloned sequence analysis
A previous study on the same 18 volunteers focusing only on bacterial resistance showed that the administration of AMC increased the amoxicillin resistant Escherichia coli and enterococci
Summary
The human colonic microbiota forms a complex ecosystem which plays important roles in human health and disease, with regard to nutrition, pathogenesis and immune function of the host [1]. The normal intestinal microbiota provides an important natural defence mechanism against invading pathogens, a process known as barrier effect. Mild or severe episodes of antibiotic associated diarrhoea (AAD) are common complications of antibiotic therapy [5]. The major form of intestinal disorders is the pseudomembranous colitis associated with Clostridium difficile which occurs in 10–20% of all AAD [6]. Multiple mechanisms occur to protect the individual against enteral pathogens: production of bacteriocins, competitive inhibition for binding to the mucosa, enhancing synthesis of mucus, and secretion of secretory IgA
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