Prevalence,antimicrobial resistance patterns and virulence gene analysis of Salmonella spp.originated from ducks in Chengdu area,China / 中国人兽共患病学报

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．