Horizontal Transfer Mechanism Of The Pathogenicity Island In Enterococci Of Swine Origin

Enterococci was originally a normal flora,now has become one of the important pathogensthat caused hospital associated infections.Enterococci can lead to urinary tract infection,reproductive tract infection,and surgical wound infections in humans and animals.It can also cause other serious infections,such as endocarditis,meningitis,and septicemia.Due to the abuse of antibiotic in clinic,the antibiotic resistance of enterococci is becoming more and more serious.Under the pressure of survival,the virulence and antibiotic resistance of enterococcus is enhancing,and even the multiple antibiotic-resistant bacteria emerges.The serious infection rate and fatality rate,which have became a thorny issue in hospital clinical treatments.The mobile elements,such as plasmids,transposons carrying antibiotic resistance genes and virulence genes for horizontal transfer,their can speedup the adaptability to the environment,enhancing the pathogenicity of the enterococci.Therefore,it isvital to study the horizontal transfer mechanism of the pathogenicity islands in enterococci.In this study,326 enterococcus strains of animal origin and 78 enterococcus strains of human origin were identified from veterinary and medical clinic,the pathogenicity island marker genes(esp,cyl M,AS)and resistance genes [erm(B),tet(M)] were detected by PCR.Conjugantion test,Sma I-PFGE,I-Ceu I-PFGE and southern blot were performed to investigate the mechanism underlying the dissemination ofthe resistant genes and co-transfer of resisance genes and pathogenicity island.The results showed that most of the Enterococci from animals and humans was E.faecalis and E.faecium,accounting for 57% and 40%,respectively.In 67 enterococcus strains of animal origin,the detection rates of esp,cyl M and AS were20 %,23.8 % and 32.8 %,respectively;the detection rates of erm(B)and tet(M)were77 % and 80 %,respectively.In 78 enterococci strains of human origin,the detection rates of esp,cyl M and AS were 47.4 %,28.2 % and 28.2 %,respectively;the detection rates of erm(B)and tet(M)were 47 % and 30%,respectively.The data showed that the detection rate of esp in enterococci of human originis higher than that of animal origin.Conjugative experiment and Sma I-PFGE shows that the erythromycin resistance gene erm(B)was transferedwith a frequency of 3.2×10-5.I-Ceu I PFGE and Southern blot results revealed that the espgene was localized on the chromosome.Along with transfer of erm(B),horizontal cotransfer of pathogenicity island occured simutaneously.S1-PFGE show that a 30 kb plasmid was present in both donors andconjugants.when the plasmidcarrying erm(B)transfered,it may play an important role in horizontal transfer of pathogenicity island.In summery,this study investigated the prevalence of pathogenicity island-associated genes in enterococci isolated from veterinary and medical clinic.It was observed that co-transfer of pathogenicity island occured along with the transfer of resistance genes simutaneously.The research on the horizontal transfer mechanism of pathogenicity island can provide a theoretical basis for the further understanding on the coevolution of resistance and pathogenicity of the enterococci,as well as the early warning of the outbreak of the enterococci infection.