Study on the Epidemiology Regularity and Phenotype Correlation of Drug-resistant Genes of Infectious Actinobacillus pleuropneumoniae in Sichuan

PurposeIn order to understand the relationship between the epidemic regularity of resistance genes and drug resistance phenotype of Actinobacillus pleuropneumoniae in some large pig farms in Sichuan Province.

MethodBacterial isolation, identification and biochemical tests were performed on the lung tissues of diseased pigs suspected of having porcine infectious pleuropneumonia and the isolates were subjected to systematic evolution analysis, drug resistance phenotype and drug- resistance gene detection.

Result11 suspected isolates of A. pleuropneumoniae were isolated from the diseased lung tissues, which were Gram-negative short rods. Biochemical tests and DNA molecular biology identified 11 isolates as A. pleuropneumoniae. The 11 isolates showed multiple drug resistance, among which the drug resistance rate of tetracycline and doxycycline was 90.90%. The drug resistance rate of lincomycin, cotrimoxazole and streptomycin was 54.55%. The drug resistance rate of clindamycin, gentamicin, chloramphenicol and florfenicol was 27.27%. The drug resistance rates to kanamycin and erythromycin were 18.18% and 9.10%, respectively. Detected 8 drug resistance genes, sul3, tetB, tetC, ermB, floR, ant(6')-Ia, aph(2'')-Id and aac(6')-Ie-aph(2'')-Ia, and the carrying rates were 100%, 40.0%, 100%, 100%, 85.7%, 14.3% and 14.3%, respectively, which were consistent with the drug-sensitive phenotype.

ConclusionThis study shows that the bacterial pathogen of fattening pigs from respiratory tract infections in large-scale pig farms in this area is A. pleuropneumoniae, which exhibits multi-drug resistance, and isolates carried more drug resistance genes and were consistent with the phenotype, which provided the basis for the prevention and control of this disease and clinical medication.