| Salmonella is one of the most important zoonotic pathogens with a wide range of hosts and can cause acute or chronic infectious diseases in human and animals.Among them,animal origin Salmonella poses a serious threat to livestock poultry farming and human health,and has important public health implications.Breeder poultry plays an important role in controlling Salmonella and is the source of the disease purification,the aim of this study is to investigate the epidemiology of Salmonella in breeder poultry farms and conduct antibiotic sensitivity tests on isolates,detect their antibiotic resistance genes and virulence genes,and select some strains for PFGE molecular typing,finally provide a scientific basis for the prevention and purification,clinical drug use and risk point control of Salmonella.From March 2018 to July 2019,a total of 2525 samples were collected from 16breeder poultry farms in 7 regions of Guangdong province,357 Salmonella strains were isolated,among them,3 strains isolated from anal swab（1.0%）,30 strains isolated from environmental samples（13.39%）,324 strains isolated from dead embryos（16.2%）and including 321 strains of chickens（19.77%）,2 strains of coturnix（11.11%）,1 strain of geese（2.44%）;The 357 Salmonella isolates belonged to 12 serotypes and the dominant serotypes in dead embryos and environment was S.pullorum and S.derby respectively;The antibiotic resistance test among the 16 antibiotics showed that 357 strains were highest resistant to sulfaisoxazole（97.76%）,followed by nalidixic acid（92.72%）,ampicillin（91.32%）and tetracycline（40.62%）.It is worth noting that the multi-drug resistance rate has reached95.24%,and the main multidrug resistance spectrum is AMP-NAL-SF;Then 22 kinds of resistance genes of the isolates were detected by PCR,results showed that the detection rate ofβ-lactam bla TEMgene was highest reaching to 98.32%,and sul2（93.84%）was the main resistance gene of sulfaisoxazole,the tetracycline resistance gene is mainly carried tet A（46.5%）,as for Quinolone Resistance Determining Region（QRDR）,there are 310 strains have single mutation of gyr A gene,and 81.29%of the strains showed mutations at position83,18.71%of the strains showed mutations at position 87,in the Plasmid-Mediated Quinolone Resistance（PMQR）genes and the efflux pump proteins encoded by the plasmid gene,only a small number of strains carried qnr S（4.76%）、qnr B（0.28%）、oqx A（7.84%）and oqx B（6.44%）.Virulence gene detection results showed that except for the low detection rate of sse L gene（51.3%）on SPI-2,all the virulence genes（spv A,spv B,spv C,spv D,spv R,mog A,mgt C,bcf A,ara B,stn,fim A）carrying rate is above 89.1%,indicating that isolates generally carried a large number of virulence genes.Finally 100 strains of SP and 25 Salmonella isolates from different sources were randomly selected for PFGE typing.The results showed that the homology between these strains was 66.01%～100%and54.63%～100%respectively.Salmonella isolates have a gene homology and genetic diversity,also the same genotype exists between different farms and different sources have the risk of cross contamination.In summary,this study conducted a systematic epidemiological survey of Salmonella in breeder poultry farms in Guangdong Province,and found that 93.75%of the investigated poultry farms were contaminated with Salmonella.Also,95.24%strains showed multi-drug resistance phenomenon.It is suggested that the hatching process and its breeding environment have been infected by Salmonella,and is necessary to strengthen the purification of Salmonella,change the medication habits and use antibiotics according to the drug sensitivity results.In addition,the presence of Salmonella with zoonosis has an infection risk for livestock and stuff,therefore,it is recommended that poultry farms should strengthen breeding management and take biosafety measures.The results of this study have further understanding of the infection and drug resistance of Salmonella in poultry farms in Guangdong province,can also provide reference for the development and implementation of Salmonella prevention and control measures for breeder farms. |
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