Yates C M, Shaw D J, Roe A J, Woolhouse M E J, Amyes S G B
Department of Medical Microbiology, University of Edinburgh, Edinburgh EH8 9AG, UK.
Biol Lett. 2006 Sep 22;2(3):463-5. doi: 10.1098/rsbl.2006.0478.
The study of antibiotic resistance has in the past focused on organisms that are pathogenic to humans or animals. However, the development of resistance in commensal organisms is of concern because of possible transfer of resistance genes to zoonotic pathogens. Conjugative plasmids are genetic elements capable of such transfer and are traditionally thought to engender a fitness burden on host bacteria. In this study, conjugative apramycin resistance plasmids isolated from newborn calves were characterized. Calves were raised on a farm that had not used apramycin or related aminoglycoside antibiotics for at least 20 months prior to sampling. Of three apramycin resistance plasmids, one was capable of transfer at very high rates and two were found to confer fitness advantages on new Escherichia coli hosts. This is the first identification of natural plasmids isolated from commensal organisms that are able to confer a fitness advantage on a new host. This work indicates that reservoirs of antibiotic resistance genes in commensal organisms might not decrease if antibiotic usage is halted.
过去,对抗生素耐药性的研究主要集中在对人类或动物致病的微生物上。然而,共生微生物中耐药性的发展令人担忧,因为耐药基因可能会转移到动物源性病原体中。接合质粒是能够进行这种转移的遗传元件,传统上认为它会给宿主细菌带来适应性负担。在本研究中,对从新生小牛中分离出的接合型阿普拉霉素耐药质粒进行了表征。小牛饲养在一个在采样前至少20个月未使用过阿普拉霉素或相关氨基糖苷类抗生素的农场。在三个阿普拉霉素耐药质粒中,一个能够以非常高的频率转移,另外两个被发现能赋予新的大肠杆菌宿主适应性优势。这是首次从共生微生物中鉴定出能够赋予新宿主适应性优势的天然质粒。这项工作表明,如果停止使用抗生素,共生微生物中的抗生素耐药基因库可能不会减少。