Mizan Shaikh, Lee Margie D, Harmon Barry G, Tkalcic Suzana, Maurer John J
Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens 30602, USA.
J Food Prot. 2002 Jun;65(6):1038-40. doi: 10.4315/0362-028x-65.6.1038.
The emergence of antibiotic resistance among important foodborne pathogens like Escherichia coli O157:H7 has become an important issue with regard to food safety. In contrast to the case for Salmonella, antibiotic resistance has been slow in its development in E. coli O157:H7 despite the presence of mobile antibiotic resistance genes in other E. coli organisms that inhabit the same animal host. We set out to determine if rumen fluid influences the transfer of plasmid-mediated, antibiotic resistance to E. coli O157:H7. A commensal E. coli strain from a dairy cow was transformed with conjugative R plasmids and served as the donor in matings with naladixic acid-resistant E. coli O157:H7. R plasmids were transferred from the donor E. coli strain to E. coli O157:H7 in both Luria-Bertani (LB) broth and rumen fluid. R plasmids were transferred at a higher frequency to E. coli O157:H7 during 6 h of incubation in rumen fluid at rates comparable to those in LB broth, indicating that conditions in rumen fluid favor the transfer of the plasmids to E. coli O157. This finding suggests that the cow's rumen is a favorable environment for the genetic exchange of plasmids between microflora and resident E. coli O157:H7 in the bovine host.
像大肠杆菌O157:H7这样重要的食源性病原体中抗生素耐药性的出现已成为食品安全方面的一个重要问题。与沙门氏菌的情况不同,尽管在同一动物宿主中的其他大肠杆菌菌株中存在可移动的抗生素耐药基因,但大肠杆菌O157:H7的抗生素耐药性发展缓慢。我们着手确定瘤胃液是否会影响质粒介导的抗生素耐药性向大肠杆菌O157:H7的转移。用接合性R质粒转化来自奶牛的共生大肠杆菌菌株,并将其用作与耐萘啶酸的大肠杆菌O157:H7进行接合试验的供体。R质粒在Luria-Bertani(LB)肉汤和瘤胃液中均从供体大肠杆菌菌株转移至大肠杆菌O157:H7。在瘤胃液中孵育6小时期间,R质粒以与LB肉汤中相当的频率转移至大肠杆菌O157:H7,这表明瘤胃液中的条件有利于质粒向大肠杆菌O157的转移。这一发现表明,奶牛的瘤胃是微生物群与牛宿主中常驻的大肠杆菌O157:H7之间进行质粒基因交换的有利环境。