| Staphylococcus aureus is widely distributed in nature.With the emergence of Methicillin-resistant Staphylococcus aureus,and many reports of Staphylococcus aureus infection in clinical,it becomes a hotspot to research Staphylococcus aureus in these years.Staphylococcus aureus can cause severe damages to both humans and animals,which makes it great sense to public health.Since 2016,a significant increase in duck embryo mortality and weak prevalence in large-scale duck embryo hatcheries in Shandong Province has been detected in our laboratory,and bacterial infection is the main cause of duck embryo death during hatching.In this study,the detection of drug resistance gene and drug susceptibility test of Staphylococcus aureus isolated from dead duck embryos were done to preliminarily grasp the drug resistance characteristics of Staphylococcus aureus in Shandong,and provide a theoretical basis for the rational use of breeding ducks.Through the detection and analysis of the virulence genes carried by Staphylococcus aureus in ducks,the pathogenicity of Staphylococcus aureus in duck embryos was presumed to understand the virulence characteristics of Staphylococcus aureus.We conducted following experiments to dead duck embryo collected since 2016 in the laboratory: bacterial isolation and culture,gram staining,16 srDNA PCR identification and nuc gene identification.Finally,we obtained 263 strains bacteria from 302 duck embryos that collected among10 batches.There were 224 duck embryos that existing bacterial infection,and the infection rate was 74.2%.Among the 263 isolates,E.coli and salmonella accounted for 29.66%(78/263)and 28.14%(74/263),and staphylococcus aureus possessed 12.17%(32/263).The results indicated that the bacterial infection should be responsible for the death increasing of duck embryos.The bacteria resistance detection of 16 common antibiotics in 32 strains of staphylococcus aureus was performed by K-B method.The results showed that 32 strains of staphylococcus aureus had resistant degree to 16 common antibiotics: the resistance to tetracycline and clindamycin was 78.13%,and the resistance to ciprofloxacin,sulfanilamide and clarithromycin was all over 60%.The staphylococcus aureus was sensitive to ampicillin,cephalothin,polymyxin B and vancomycin(2.5%-100%).The staphylococcus aureus strains isolated in this study possessed the feature of multidrug-resistant.According to the present research,we should give priority to the usage of cephalosporins and ampicillin in the treatment of bacterial infection in duck flocks.At the same time,we suggested that different medicine should be used in clinical treatment,and antibiotics should be used more scientifically and rationally.The antimicrobial resistance genes of quinolones among 32 strains staphylococcus aureus were detected by PCR.The results showed that the resistance genes of msrA and ermC were common in duck embryo-origin staphylococcus aureus.The detection rate of msrA and ermC was 40.62% and 53.13%.The carrying rate of these two genes was 25%.Four virulence factors among the 32 strains of staphylococcus aureus were investigated by PCR screening.The detection rates of hla,hlb,clfa and pvl were 81.25%?71.88%?78.13% and 6.25% respectively.Thereinto 27 strains possessed more than 2 virulence genes.Bacteria carrying two virulence genes was 21.9%;bacteria carrying three virulence genes was 59.4%.One strain was detected possessed four virulence genes.The results show that most duck-embryo-origin staphylococcus aureus isolated in Shandong province possessed multiple virulence genes,which might lead to the high-virulent features of staphylococcus aureus.Based on our research,one of the important reasons for the death of embryos we collected were bacterial infection.Thereinto,the staphylococcus aureus we isolated possessed the property of resistance to multi-drugs,which also possessed many virulence geness and drug resistance genes.These features may make the staphylococcus aureus show high level pathogenicity,which will be harmful to breeding industry. |
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