Antibiotic-Induced Gut Microbiome Disruption

Gut microbiota is experimentally disrupted by administering broad-spectrum antibiotics (ampicillin, neomycin, metronidazole and vancomycin) in the drinking water [12 (link), 13 (link), 15 (link), 17 (link)]. Since this route of administration would result in severe dehydration and subsequently affect the host immunity [33 (link), 34 (link)], we used a modified protocol. The mice were given 0.2 ml of the following broad-spectrum antibiotics– 10 mg/ml ampicillin (Amresco), 10 mg/ml neomycin sulfate (Amresco) and 5 mg/ml metronidazole (Hualu Holding Co., Ltd.)–twice daily for 3 weeks by oral gavage. Vancomycin was excluded since it might have had an impact on the pneumococcal infection. To ensure that the other antibiotics had no effect on pneumococcal infection, and to test any potential antibacterial effect of murine blood and tissues, S. pneumoniae was co-cultured with the sera, and the lung or liver homogenates of the gut microbiota-disrupted mice, prior to initiating the infection (S1 Table).