Isolation,Identification Of Bacteria In Diarrhea Piglets From Large-scale Pig Farms In Hainan Province

Piglet diarrhea is a common disease of piglets,and its etiology is complex,including non-infectious and infectious factors.Among the piglet diarrhea caused by infectious factors,bacterial piglet diarrhea has caused huge economic losses to the stockbreeding due to its high morbidity,high mortality,and difficulty in prevention and control.Antibiotic therapy is a common method to treat bacterial diseases.Due to the irregular use of antibiotics,the resistance of bacteria continues to increase,which causes increasing damage to the stockbreeding.Because Hainan Province is warm and humid,and the environmental conditions are suitable for the growth of pathogenic bacteria,this study chose to isolate and identify the pathogen of bacterial diarrhea in piglets on large-scale pig farms in Hainan Province,and evaluate its drug resistance,which is the indicator of bacterial pathogenicity in large-scale farms in this region.Provides guidance on the prevention and treatment of piglet diarrhea.In this study,piglets with diarrhea from 5 large-scale pig farms in Hainan province were examined and their digestive tract lesions were recorded.Bacteria isolation and identification,virulence gene,drug resistance phenotype and drug resistance gene were studied on anal swabs and small intestinal tissue samples of piglets by inoculation medium identification,physiological and biochemical analysis,molecular biology classification and K-B drug susceptibility test.The main contents and results are as follows:1.Isolation and identification of enteropathogenic bacteriaFrom February 2021 to February 2022,550 anal swabs and small intestinal tissue samples of diarrheal piglets were collected from 5 large-scale pig farms in different cities in Hainan Province.A total of 164 strains of ETEC,10 strains of Salmonella,1 strain of Shigella and 1 strain of Pseudomonas aeruginosa were isolated and identified,with isolation rates of 30%（164/550）,1.8%（10/550）,0.18%（1/550）and 0.18%（1/550）,respectively.2.The identification of enteropathogenic bacteria’s virulence factorsAmong 164 strains of enterotoxin-producing E.coli isolated from 5 large-scale pig farms in different areas of Hainan Province,164 strains（100%）carried adhesin F4,and 137strains（83.5%）carried both ST and LT.23（14.1%）strains only carried ST,4 strains（2.4%）only carried LT,and ETEC carrying adhesins F5 and F6 were not found.The results showed that the main virulence factor combination of ETEC isolated from Hainan province was F4+ST+LT.3.Study on the drug resistance of enteropathogenic bacteria（1）The 164 strains of ETEC isolated and identified from Hainan province were all resistant to more than 3 of the 14 antibiotics with serious drug resistance.The strains of ETEC to ampicillin,penicillin,fluorine,chloramphenicol,doxycycline,erythromycin resistant rate of more than 90%,to amoxicillin,ciprofloxacin,enrofloxacin and minocycline resistant rate were from 50%to 90%,to gentamycin,kanamycin,streptomycin,and cotrimoxazole resistance were below 50%;The 137 strains of ETEC were multidrug-resistant strains,and the most of strains were resistant to 8 antibiotics,accounting for 23.7%（39/164）.Compared with the resistance rate of 164 ETEC strains to other antibiotics,the resistance rate of kanamycin,gentamicin and streptomycin in aminoglycoside antibiotics was lower.（2）The 10 Salmonella strains isolated and identified from Hainan province were severely resistant to ampicillin,penicillin,amoxicillin,doxycycline,florfenicol,gentamicin,kanamycin,streptomycin,minocycline and erythromycin,and the drug resistance rate reached 100%（10/10）.Antibiotic resistance rates to ciprofloxacin,enrofloxacin and chloramphenicol were 60%,20%and 20%,respectively.All Salmonella isolates were resistant to antibiotic 3 or above.Therefore,10 Salmonella enteritidis isolates from Hainan province were all multidrug resistant strains.Compared with the resistance rates of 10salmonella enteritis strains to other antibiotics,the resistance rates of ciprofloxacin,enrofloxacin and chloramphenicol were lower.（3）The isolated Shigella strain was resistant to 13 antibiotics except kanamycin.Pseudomonas aeruginosa was sensitive to kanamycin,gentamicin,streptomycin,ciprofloxacin and cotrimoxazole,and resistant to the other 9antibiotics.4.Identification of drug resistance genes of enteropathogenic bacteria ETEC and Salmonella.15 kinds of drug resistance genes were detected in ETEC and Salmonella.The results showed that ETEC and Salmonella from pigs in Hainan Province carried multiple drug resistance genes,mainly bla _TEM、bla _CTX-M、aph A2、sul II、tet A、flo R.The detection results of drug susceptibility test and drug resistance gene showed thatβ-lactam,tetracycline,amido alcohol,macrolide,quinolone,aminoglycosides antibiotic resistance gene and drug resistance phenotype had a high coincidence rate but sulfonamide antibiotic resistance genes and resistance phenotype coincidence rate is low.