The Study On Identification And Drug Resistance Of Salmonella In Chicken Farms

Objective:Salmonellosis is one of important zoonotic diseases on public health.chicken are one of the most important reservoir and can spread pathogens of animal infectious diseases.Its mortality can reach to 80% when the outbreak of Salmonellosis is happened in chickens. Chickens can happened an acute or chronic disease when any one or more members of Salmonella are in chickens. Pathogenic salmonella in chickens including pullorum, fowl typhoid and paratyphoid. They exist in the poultry industry generally and can decline the product performance of chickens and decrease egg hatching rate of chickens and often caused massive morbidity and mortality in chickens and lead to serious economic losses. The drug resistance of chickens to Salmonella is increased when the chickens is under the antibiotic selective pressure by irrational use of antibiotics in chickens. The prevalence of salmonella in different chick farms in the city of Dehui were investigated, sick chickens were collectted from 7 different farms and Salmonella were isolated.5 pathogenic salmonella which were isolated from 5 different farms seperately have had drug sensitivity test and minimal inhibitory concentration determination and the united susceptibility testing.Drug resistance of Salmonella which were seperated had been determined so this can be a reference for rational use of drug in chickens.Method:In this study we have collected the sick chicken from seven different chicken farms in the city of Dehui and Salmonella were separated from blood in heart, liver, spleen, lung and intestinal contents of the sick chicken respectively.These Salmonella were cultured in HE and SS culture medium respectively, colonies which were typical were picked and coated puncture culture in triple sugar iron slant medium, then these Salmonella were identified by gram staining and serological testings. There were 5 strains which were serological response positive significantly from different chicken farms were selected and inoculated in health chicken which were 1 day old seperately and set the control group of chickens. These chickens were reared under appropriate conditions seperately. Their morbidity and mortality were observed.The pathological changes of chickens which were died were checked. The drug sensitivity of the 5 virulent strains were tested by using 8 kinds of drugs and 29 kinds of drugs which were used in farms in the city of Dehui according to Kirby-Bauer disk diffusion method. Minimum inhibitory concentration of the 5 virulent strains of Salmonella were determinated by using of amikacin, ciprofloxacin, chloramphenicol, doxycycline, norfloxacin, gentamicin and enrofloxacin mequindox eight drugs. Combined drug susceptibility of the 5 virulent strains of Salmonella were tested by mequindox and norfloxacin, enrofloxacin, ciprofloxacin, chloramphenicol or doxycycline seperately.Result:There are 150 tissue samples were collected from 7 farms in the city of Dehui and 17 strains were positive by serum hemagglutination reaction. Animal experimental inoculations showed that the 5 Salmonella strains which were serological response positive significantly from different chicken farms were virulent strains.The drug sensitivity tests of the 5 virulent strains by using 26 kinds of drugs according to Kirby-Bauer disk diffusion method showed that there were 4 strains were all exhibited strong drug resistance to majority drug. There is only S-2 strain show sensitive to aminoglycosides, cephalosporins and synthetic antibiotics.There are S-1,S-2,S-3,S-5 strains show moderate-intensity resistance to polymyxin. In addition,there is S-2 strain showed sensitive to ceftriaxone and cefotaxime and S-3,S-4 strain show moderate-intensity resistance to cephalosporins and is still sensitive to cefotaxime. There are 60% sensitivity rates to cefotaxime, suggesting that cefotaxime can be applied in the clinical treatment of chicken in the city of Dehui.Minimum inhibitory concentration of the 5 virulent strains of Salmonella were determinated by using of amikacin, ciprofloxacin, chloramphenicol, doxycycline, norfloxacin, gentamicin and enrofloxacin mequindox eight drugs showed that they were sensitive to mequindox, enrofloxacin and they were strong antibiotic resistance to the others. Mequindox and norfloxacin, enrofloxacin, ciprofloxacin, chloramphenicol or doxycycline five drugs do not have synergistic and additive effect, and most of them had nothing to do or antagonism by combined drug susceptibility of the 5 virulent strains of Salmonella were tested.Conclusion:The prevalence of Salmonella gallinarum was in most of farms in the city of Dehui. Salmonella strains in poultry had a wide range of drug resistance and sensitive to most drugs no longer. Cefotaxime and ceftriaxone which belong to Cephalosporins were effective relatively. Mequindox and norfloxacin, enrofloxacin, ciprofloxacin, chloramphenicol or doxycycline five drugs do not have synergistic and additive effect, and most of them has nothing to do or antagonism...