Effects of Antibiotics on Bacterial Species Composition and Metabolic Activities in Chemostats Containing Defined Populations of Human Gut Microorganisms

Abstract

The composition and metabolic activities of the human colonic microbiota are modulated by a number of external factors, including diet and antibiotic therapy. Changes in the structure and metabolism of the gut microbiota may have long-term consequences for host health. The large intestine harbors a complex microbial ecosystem comprising several hundreds of different bacterial species, which complicates investigations on intestinal physiology and ecology. To facilitate such studies, a highly simplified microbiota consisting of 14 anaerobic and facultatively anaerobic organisms (Bacteroides thetaiotaomicron, Bacteroides vulgatus, Bifidobacterium longum, Bifidobacterium infantis, Bifidobacterium pseudolongum, Bifidobacterium adolescentis, Clostridium butyricum, C. perfringens, C. bifermentans, C. innocuum, Escherichia coli, Enterococcus faecalis, Enterococcus faecium, Lactobacillus acidophilus) was used in this investigation. Ampicillin [9.2 g (ml culture) ؊1 ] was added to two chemostats operated at different dilution rates (D; 0.10 h ؊1 and 0.21 h ؊1 ), and metronidazole [76.9 g (ml culture) ؊1 ] was added to a third vessel (D ‫؍‬ 0.21 h ؊1 ). Perturbations in bacterial physiology and metabolism were sampled over a 48-h period. Lactobacillus acidophilus and C. bifermentans populations did not establish in the fermentors under the imposed growth conditions. Ampicillin resulted in substantial reductions in bacteroides and C. perfringens populations at both dilution rates. Metronidazole strongly affected bacteroides communities but had no effect on bifidobacterial communities. The bacteriostatic effect of ampicillin on bifidobacterial species was growth rate dependent. Several metabolic activities were affected by antibiotic addition, including fermentation product formation and enzyme synthesis. The growth of antibiotic-resistant bifidobacteria in the large bowel may enable them to occupy ecological niches left vacant after antibiotic administration, preventing colonization by pathogenic species.

Clostridium difficile colonization and antibiotics response in PolyFermS continuous model mimicking elderly intestinal fermentation

“…In our model we chose to apply a higher antibiotic concentration (333 mg L −1 , twice daily) to account for the high total cell numbers tested in TDC (in the range of log 10 11.1–11.2 GC mL −1 [19]). Furthermore, we considered that the concentration of metronidazole entering the colon is higher than that tested in feces since the gut bacteria metabolize the drug [40]. With our conditions, we observed a strong reduction of CD numbers while toxin production decreased below the detection limits.…”

Clinical chorioamnionitis at term VIII: a rapid MMP-8 test for the identification of intra-amniotic inflammation

“…For newborns, consequences from prenatal exposure to antibiotics include: 1) the need for a sepsis work-up and other laboratory testing, which is associated with increased workload and costs (108-114); 2) a prolonged hospital stay that can predispose these neonates to acquire infections caused by multi-drug-resistant bacteria (110, 112); 3) the separation of newborns from parents with the potential for impaired mother-neonate bonding and breastfeeding; and 4) the alteration of gut microbiota (125-128). The change in neonatal gut microbiota due to intrapartum antibiotic exposure is currently a subject of intense investigation.…”

Changes in Composition and Function of Human Intestinal Microbiota Exposed to Chlorpyrifos in Oil as Assessed by the SHIME® Model

“…Given the gut microbiota’s key role in host homeostasis, factors such as antibiotics [25,26], diet [27] and toxics (including pesticides) [10,11,28,29] can influence the intestine microbiota composition. In rodent models, chronic exposure to pesticide-contaminated foods leads to gut microflora dysbiosis; more specifically, the abundance of Lactobacillaceae fell significantly during CPF exposure [11,29].…”