Investigation Of Microorganisms Carried By Poultry Eggs In Shanghai And Analysis Of The Characteristics Of Two Common Pathogenic Bacteria

Eggs are a high-quality,affordable,and nutritious source of proteins on people’s dining tables.As a major country for poultry eggs production and consumption,China has been producing the largest amount of eggs in the world for more than 20 years.The quality and safety of poultry eggs has been paid more and more attention,and the most important problems are the contamination of pathogenic microorganisms carried by poultry eggs.It can not only damage the quality of eggs,cause huge economic losses,but also pose a threat to human health.Shanghai is the most populous city in China,with a huge daily consumption of poultry eggs.However,the contaminations of microorganisms carried by poultry eggs are currently unclear.Therefore,the poultry eggs were collected systematically from local farms and farmers’ markets in Shanghai,and the microorganisms on the surface and contents of the eggs were investigated.Then the biological characteristics of pathogenic Escherichia coli and Staphylococcus aureus were analyzed.This study will help us to understand the species of microorganisms of eggs and the biological characteristics of foodborne pathogens in Shanghai.To achieve these goals,the samples of chicken eggs,pigeon eggs,duck eggs,and quail eggs were collected from chicken farms and farmers’ markets in Shanghai,and the bacteria were separated from the surface and content of poultry eggs.A fully automatic rapid microbial mass spectrometry detection system(ARMMSDS)was used to identify microbial species carried by poultry eggs.Subsequently,the important foodborne pathogenic microorganisms(E.coli and S.aureus)were tested for biochemical,virulence genes,pathogenicity,drug resistances and resistance genes.The detail contents and results in this study are as follows:(1)420 poultry eggs were collected from local farms and farmers’ markets in different regions of Shanghai,and the bacteria from surface and content samples of eggs were identified using ARMMSDS.337 bacterial strains were successfully isolated,belonging to 57 different bacterial species.Among them,the most number strains were isolated from chicken eggs(n=252),followed by pigeon eggs(n=46),duck eggs(n=27),and quail eggs(n=12).The most prevalence genera were Staphylococcus(43.79%)and Enterococcus(14.50%);The most prevalence bacteria were Staphylococcus sciuri(12.13%)and E.coli(11.54%),and Salmonella was not detected;There are significant differences in bacterial species among sampling elements,poultry egg types,and sampling regions.(2)Ten strains of E.coli identified by ARMMSDS were randomly selected for serotype identification,and two strains were enterotoxigenic E.coli,with the serotypes O7:K1 and O78:K80(B),respectively.Both bacteria carried 7 virulence genes,including fim C,mat,ibe B,yij P,omp A,iss,and iro N.The O7:K1 strain also carried 5virulence genes,including pap C,tsh,cva C,iuc D,and irp2,with stronger toxicity.O7:K1 could cause obvious clinical symptoms and death in mice,while O78:K80(B)did not cause mouse death.Both strains were resistant to 11 antibiotics,and carried three resistance genes,including sul2,aph(3 ’)-Ia and gyr A.(3)Three strains of S.aureus identified by ARMMSDS were selected to culture,biochemical identification,and PCR amplification.The results showed that all strains belonged to atypical S.aureus.All the strains carried hemolysin related virulence genes,including hla,hlb,hld,hlg,and hlg-2.Animal experiments showed low toxicity for three S.aureus,and no obvious pathogenicity and deaths were observed in mice.All S.aureus present multidrug resistance,and developed drug resistance to seven antibiotics simultaneously.Two resistance genes were found,including grl B and fex A gene.In summary,this is the first time to systematically and comprehensively study the microorganisms on surface and content of poultry eggs from local farms and farmers’ markets in different regions of Shanghai.The isolated microorganisms from poultry eggs characterized by a wide distribution and had multiple influencing factors.Many zoonotic pathogens were found in eggs,and need to be pay more attention.This study is of great significance for comprehensively understanding the infection situation of microorganisms in poultry eggs in Shanghai,and help us to know the pathogenic bacteria species in egg.These results will help us to formulating prevention and control measures for pathogenic bacteria pollution in poultry egg products,and ensure the food safety of poultry eggs.