Analysis On The Phylogenetic Group,Pathogenicity And Drug Resistance Of Non-O157 STEC From Cattle In Parts Of Xinjiang

To study the virulence genes,drug resistance phenotypes and drug resistance genes carried by STEC in different regions of Xinjiang,and to discuss the epidemic characteristics and spread law of STEC drug resistance in cattle source of Xinjiang preliminarily.From 2015 to 2017,1459 samples of anal swabs,feces,feed,drinking water and carcass from cattle farms and slaughtering plants in bole,yili,changji,shihezi,wujiaqui and urumqi were collected,and a total of 209 strains of non-o157 STEC were obtained.1.Quadruple PCR detection of E.coli phylogenetic group in 209 strains of non-O157 STEC,and the chuA,yiaA,arpA and TspE4.C2 genes were amplified.Virulence genes of 209 strains of non-o157 STEC were detected,eaeA and Hly genes were amplified by PCR,and some strains were tested for pathogenicity in mice.The susceptibility of 209 non-O157 STECs to 17 antibiotics was tested by K-B method,and the resistance genes,plasmid and integrons were detected by PCR.The conjugation test of ESBLs-producing strains was carried out to verify the horizontal transfer of resistance genes.The phylogenetic group results results showed that 209 strains of non-o157 STEC belonged to group A,Bl,E,D and F,among which 0.96%belonged to group D,which was associated with pathogenic bacteria.Group A,group E,group B1 and group F were 94.74%(198/209),2.39%(5/209),0.48%(1/209)and 1.43%(3/209),respectively.Among the 209 strains of STEC,48.33%(101/209)were carrying Hly gene,while 23.44%(49/209)were carrying Stx1,Stx2 and Hly.eaeA gene was not detected.The median lethal dose test showed that the mice began to die after 48 h.All mice in 2.8×108 CFU mL-1 groups were tolerant.Some mice in 2.8×109 CFU·mL-1,2.8×1010 CFU·mL-1 and 2.8×1011 CFU·mL-1 groups were tolerant.All mice in 2.8×1012 CFU mL-1 group died.LD50 was calculated to be 0.8×1010 CFU mL-1.according to the modified Koch method.Among the 209 STEC strains,23(11%)were drug-resistant.Among them,9 strains(4.31%)were multidrug resistant to 3?10 antibiotics.The most common resistance pattern was CHL+STR+TET,Ampicillin resistance was the most common.blaTEM and blaCTX-M were the major genotypes of four strains(1.91%)that produced ESBLs.Some strains also carry tetA gene(tetracycline resistance),sulI gene(sulfanilamide resistance)and cmlA,In the resistant strain detected only 1 type of plasmid,I class integrase gene detection rate of 13%.Drug resistance phenotypes and genes carried by bovine STEC can be transferred horizontally among bacteria.Most of the non-o157 STEC from cattle in xinjiang belong to group A,mainly carrying Hly gene and with certain pathogenicity.The drug resistance level of STEC from cattle in different regions is not high,but there are esbls-resistant strains.This is the first time that blaTEM and blaCTX-M have been detected in bovine STEC in Xinjiang.The multidrug resistance of xinjiang cattle STEC may be caused by the virulence and drug resistance genes of non-pathogenic escherichia coli.The selection pressure of antibiotics in different areas and cattle farms leads to the great difference of antibiotic resistance.