The Serogroups, Antimicrobial Resistance And Virulence Genes Of Escherichia Coli Isolates From Diarrheic Sika Deer (Cervus Nippon) In Northeastern China

A total of 282 E.coli isolates were collected from diarrheic sika deer (Cervus nippon) of different nursery in three provinces of the Northeastern China from 2004 to 2006. Firstly, we used the BTB base to identify the E.coli by routine laboratory methods, observed the shape by microscope, then the biochemical event was carried out.This study was performed to investigate the distribution of serogroups, antibacterial susceptibility and virulence genes among 282 Escherichia coli strains. Of these E. coli isolates, 186 were determined to be placed in different serogroups, 65 were unable to be serogrouped and the rest 31 auto-agglutinated. These isolates distributed in 54 serogroups and 99 (53.2%) belonged to 13 O serogroups: O2, O3, O7, O9, O21, O26, O77, O87, O126, O128, O138, O142 and O154, and several uncommon O serogroups were discovered in this study.The susceptibility of 15 antibacterial agents to all 282 E.coli strains was assessed by means of microdilution WHO recommended, according to NCCLS, with the control strain ATCC25922. The results showed high resistance frequencies in E. coli tested, resistance was most frequent for sulfamethoxazole (84.0%), tetracycline (80.5%), ampicillin (69.1%) and chloramphenicol (62.1%), gentamicin (53.9%), cephalothin (47.2%) and amikacin (47.2%). Most of the strains showed multi-resistance: 92.6% of the isolates were resistant to at least three antibiotics, 78.0% were resistant to at least five antibiotics. Additionally, we detected the frequency of resistance genes including tetA, tetB, tetC, aadA, strA, strB, sul1, sul2, sul3. The results revealed that most of these resistance genes were generally present, even multidrug resistant. It is important to emphasize the rational use and administion of antibacterial agents.Simultaneously, we detected the stx1,stx2 and astA of E.coli Shiga toxin and EAST1, and the detection rate were: stx1,24.47%(69/282);stx2, 26.6%(75/282);astA, 41.8%(118/282). Such high frequency would influence the animal cultivation and production, even the hunman health.To our knowledge, this is first report of E. coli isolates systematically collected from sika deer.