| Salmonella is an important zoonotic pathogen.Pigs infected with Salmonella can cause diarrhea,fever,gastroenteritis and even sepsis,affecting sows reproduction,causing significant economic losses to the aquaculture industry.According to the latest statistics,there are more than Salmonella serotypes and China has reported at least 292 serotypes.Because of its serious harm to animal husbandry,public health and food safety,it is of great significance to grasp the distribution of the epidemic situation of Salmonella surveillance to help prevent and control early.In this paper epidemiological investigation and biological control were studied.In this study,a total of 1629 fecal samples were collected from different pig farms in Jiangsu and Anhui from 2015 to 2016,a total of 175 Salmonella isolates were isolated and the average isolation rate was 10.74%.The isolation rate was 22.83%in summer,11.46%in autumn,5.95%in winter and 3.19%in spring which showed obvious season difference.The isolation rate between different age pigs was also different.Among them,26.97%in boars,17.57%in sows,10.3%in nursery pigs(31-70 days old),7.88%in fattening pigs(71 days and above)and 0%in piglets(1-30 days of age).In terms of geographical area,the highest separation rate is 15.61%of Suqian,followed by Zhenjiang 12.57%,Jiangsu Wuxi 11.11%,Maanshan 7.85%,Chuzhou 7.02%,There was seven serotypes were isolated which are Salmonella typhimurium,Salmonella derby,Salmonella London,Salmonella rissen,Salmonella reading,Salmonella Newlands and Salmonella okefoko,in which Salmonella accounting for 58.29%.93 of the isolated Salmonella were selected for pulsed field gel electrophoresis(PFGE),which were divided into 22 PFGE types.The results of the survey revealed the prevalence of Salmonella in these areas,and provided reliable data for the prevention and control of Salmonella.Minimum inhibitory concentration(MIC)to 12 antibiotics of the 102 Salmonella Typhimurium isolated in this test were determined,101 showed multiple drug resistance and the drug resistance rate was 99.02%.Among them,48.04%of the Salmonella Typhimurium resistant to 4-6 antibiotics,41.08%resistant to 7-9 antibiotics,resistant to 4?6 antibiotics,in particular,there is also 1 Salmonella Typhimurium resistant to 10 antibiotics.With the natural resistance of Salmonella strains more and more,the development of new antibiotic alternatives become a top priority.85 Salmonella bacteriophages were isolated from the faeces and sewage samples of pig farms.There host range were detected and a phage named SQC73 showed a wide host range and good lysis ability.Transmission electron microscopy showed that the phage SQC73 has a positive icosahedral head,non-shrinkable tail,consistent with the characteristics of long-tail virus.The biological characteristic were identified the pH and thermostability,optimal multiplicity of infection(MOI)and one-step growth experiment.It showed excellent tolerance to pH and temperature.The MOI 100:1,the latent period was 20 min,the burst period was 70 min and the average burst size was 25.3 phages per cell.In sterilization effect test,SQC73 killed more than 99%of the salmonella on agar plate.In simulated pollution test,SQC73 killed more than 96%of the salmonella which showed excellent potential as environmental disinfectants... |
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