影响试管群落中耐药大肠杆菌比例因素的研究

A Study on Factors Influencing Dynamics Variation of the Resistant E. coli Ratio

关键词:  人造微生物群落  耐氨苄西林大肠杆菌  菌落比例  影印培养法

Key words:  Synthetic microbial community  Ampicillin-resistant Escherichia coli  Colony ratio  Replica plating method

摘要:

研究耐药菌株和敏感菌株的竞争关系，为寻找降低耐药细菌危害的方法提供理论依据。应用改良影印培养法，考察耐氨苄西林大肠杆菌菌株（G414）起始比例、益生菌种类和营养水平对人造微生物群落中G414菌落比例变化的影响。结果表明：人造群落中耐药菌株生存竞争能力大于敏感菌株（ATCC 25922），其比例在1~7 d均逐渐上升；高初始比例组的耐药菌株比例从33%上升至64%，绝对值增加31%，超过敏感菌株成为群落中的优势菌，低初始比例组从10%上升至43%；枯草芽孢杆菌和地衣芽孢杆菌在1~7 d能够显著放缓耐药株在群落中比例的升高趋势（P<0.05），蜡样芽孢杆菌除开始两天外，可极显著地降低耐药菌株的比例（P<0.01）；在高（100%）、中（10%）、低（1%）营养条件下，耐药菌株比例均逐步升高，中营养水平组的比例上升最快。耐氨苄西林大肠杆菌菌株并没有因携带耐药基因而升高其在无药环境中的竞争适应度代价，反而获得了在正常营养和低营养以及多物种竞争条件下的某种竞争优势，逐步成为人造群落中的优势菌群，传播出去，可能对公共卫生安全造成较大威胁；枯草芽孢杆菌和地衣芽孢杆菌只能降低耐药菌株比例上升的趋势，而蜡样芽孢杆菌可极显著地抑制耐药菌株的生长，促使其消亡，加以开发利用，或许能降低养殖环境中某些耐药菌的数量。

Abstract:

To study the competitive relationship between drug-resistant and sensitive strain so as to provide theoretical basi for reducing the burden of bacterial drug-resistance. Method: Three factors of initial ampicillin-resistant E.coli (G414) ratio, profitable bacillus strains and utritional levels were investigated by Replica plating method with the resistant E.coli ratio. Results: The competitive fitness of resistant E.coli was greater than sensitive strain (ATCC 25922) in synthetic microbial communities, and the resistant strain ratio increased gradually in 1~7 days. The resistant strain ratio increased from 33% to 64% in the higher initial value group that made it become the dominant strain in the community, while the lower initial value group increased from 10% to 43%. B.subtilis and B.licheniformis could significantly diminish the the rising trend of resistant strain in the community within 1~7 days(P<0.05),while B.cereus significantly reduced the ratio of resistant strain except first two days(P<0.01). Resistant strain ratio rose gradually both in higher(100%), medium(10%) and lower(1%) nutritional levels, but the medium nutritional level group rose the most . Conclusions: The ampicillin-resistant E.coli (G414) did not increase its competitive fitness cost in the antibiotic-free environment by carrying ampicillin-resistant genes. Instead, it obtained some competitive advantage in the conditions of normal or low nutrition and multi-species competition, gradually became the dominant strain in the artificial community.If spread, it will pose threats to public health security. B.subtilis and B.licheniformis could only diminish the rising tendency of resistant strain, while B.cereus could significantly inhibit the growth of resistant strain. It is quite possible for reducing the number of resistant strain in feeding environment if the profitable bacillus strain is developed and fully utilized.