ABSTRACT
We investigated the contamination,antimicrobial resistance and the virulence genes carriage of Salmonella spp. in duck slaughter chain.Suspected strains were isolated from slaughterhouse samples according to GB 4789.4-2010 and identi-fied by duplex PCR,and then the positive strains were used for serotype analysis.Subsequently,positive strains were tested against 10 different antimicrobial agents using Kirby-Bauer disk diffusion method,the results were determined on the basis of CLSI standard.Finally,9 virulence genes were detected among positive strains by PCR.The results showed that 9 9 Salmonella isolates were recovered from 343 samples and total isolation rate was 28.86%.The prevalence of Salmonella before slaughte-ring,at depilation stage,at evisceration stage,in duck meat and after slaughtering was 45.71%,22.68%,24.72%, 38.33% and 25.81%,respectively.Seven serotypes were de-tected and most of them were S.Indiana,S.Newlands,S. Anatum.The Salmonella isolates were most frequently re-sistant to nalidixic acid(91.92%),the resistance rates of tet-racycline (43.43%),ampicillin (42.42%),trimethoprim-sulfamethoxazole (34.34%),ciprofloxacin (29.29%),ceftri-axone (27.27%),gentamycin (24.24%),and kanamycin (22.22%)were at a medium level.The resistance rates of amoxicillin-clavulanic acid (9.09%)and minocycline (6.06%)were relatively low.The multi-drug resistance rate of Salmonella isolates,which was 47.47%,showed a high especially in S.Indi-ana,S.Typhi and S.Typhimurium.It was notable that the harboring rates of virulence gene spvR(94.95%),avrA (93.94%),ssaQ(90.91%),mgtC(87.88%),sopB(83.84%),bcfC(80.81%),siiD(77.78%)among Salmonella isolates were at high level,in contrast to the lower carriage rates of spvB(29.29%),spvC (11.11%).In summary,the results indica-ted that the duck slaughter chain was easily contaminated by Salmonella spp.with different serotypes,different antibiotic re-sistant patterns and high virulence genes harboring rate.Relevant slaughterhouse and departments should strengthen supervi-sion in sanitation and manage the use of antimicrobial agents,to guarantee food safety and public health．
ABSTRACT
To investigate the contamination conditions of Campylobacter spp.in duck production chain and its antimicrobial resistance,virulence gene distribution,samples were collected at the duck slaughterhouse according to GB 4789.9-2014.Triplex PCR assay was applied to identify the species of Campylobacter and the recovered Campylobacter strains were tested for the antimicrobial susceptibility against 8 kinds of antimicrobial agents using a broth microdilution method,the susceptibility results were determined according to the NARMS criteria (2011).Subsequently,4 virulence genes were detected by PCR method.The result showed that 187 Campylobacter isolates were obtained from 489 samples,including 160 C.jejuni,130 C.coli and 10 unidentified Campylobacter isolates.The total isolation rate of Campylobacter was 38.24％.The prevalence of Camnpytobacter before slaughtering,at depilation stage,evisceration stage and duck products was 76.33％,5.62％,24.00％,and 0％,respectively.The Campylobacter isolates were most frequently resistant to tetracycline (95.72 ％),followed by resistance to clindamycin(90.91％),the resistance rate of azithromycin (63.64％) was in the middle,the resistance rates of ciprofloxacin(31.02％),gentamicin(34.76％),nalidixic acid (37.43 ％),erythromycin (41.18 ％),chloramphenicol (41.18％) were relatively low.The multi-drug resistance was common among Campylobacter isolates with a rate of 72.19％.The prevalence of adhesion-associated gene cadF,flagellin gene flaA,invasion associated protein gene iamA,toxin regulation gene cdtB was 100％,80.75 ％,71.12％ and 94.65％,respectively.The results indicated that the Campylobacter contamination occurred in the slaughtering procedures of duck,and the antimicrobial resistance of Campylobacter isolates was relatively serious.In addition,the virulence-associated genes were detected widely among Campylobacter isolates.Therefore,the supervision of antimicrobial agents using at rearing stage should be strengthened,along with health management in duck production chain.