| Objective:Analyze the epidemiological data of human Streptococcus suis(S.suis)infection cases in Shenzhen from 2005 to 2021 to understand the epidemic characteristics,trends,and clinical classification.Carry out genomic analysis on S.suis strains isolated from cases to describe the serotypes,molecular types,virulence factors,and carrying of drug resistance genes of human strains in Shenzhen.Analyze the possible sources of human S.suis infections from a phylogenetic perspective to provide evidence for the prevention and control of the disease.Conduct drug sensitivity tests to understand the resistance levels of human S.suis strains to antibiotics,and provide data support for clinical medication.In addition,use genomic technology to predict the risk of human infection by S.suis carried in swine.Methods:The epidemiological information of 43 cases of human infection with S suis in Shenzhen from 2005 to 2021 was collected from the infectious disease Reporting Information Management system of the Chinese Center for Disease Control and Prevention,and the distribution of spatial,temporal and population distribution was described.A total of 100 tonsil samples of live swine were collected for the isolation and identification of S.suis,and the isolation rate was counted.X2 test was used to analyze whether there were differences in the carrying rate of S.suis among pigs from different regions flowing into Shenzhen.Based on the National Pathogenic bacteria identification Network,33 strains of S.suis from 33 cases were collected.With the help of whole genome sequencing technology,the isolated strains of human and swine were sequenced.Based on the sequencing results,the serotype and multilocus sequence typing(MLST)of S.suis were analyzed,and virulence genes and drug resistance genes were detected.The genetic relationships between 33 strains of human S.suis from Shenzhen and global strains were analyzed.At the same time,the sensitivity of all strains to antibiotic drugs was tested.Results:Epidemiological data showed that the annual number of cases in Shenzhen from2005 to 2021 ranged from 0 to 6,with the largest number of reported cases in 2021.The peak of the disease occurred in June and July.All cases of human infection with S.suis were sporadic cases without obvious regional clustering.The cases were mainly young and middle-aged males with an average age of 50.13 years old.Most of them were cooks and pork retail employees who had close contact with raw pork.At the same time,there were 2 cases of patients who had no contact with pork and got sick from touching or eating chicken and ducks.The main clinical manifestations were meningitis and septicemia.Two cases developed streptococcal toxic-shock-like syndrome(STSLS)and died,with a fatality rate of 5.56%.The human strains in Shenzhen were mainly serotype2,followed by serotype 14.The main popular ST types were ST1 and ST7.In addition,ST242,which is rarely reported,and ST25,which is rare in China,were found.38 strains from swine were isolated,with an isolation rate of 38%.The serotypes of swine strains were abundant,mainly serotype 2.The popular ST types were ST1 and ST28,and 8 new ST types were discovered.According to the core-genome Single Nucleotide Polymorphisms(core-SNPs)evolution distance and the subgroups of clonal complex,Shenzhen human serotype 2 strains were mainly genetically close to Vietnam,Guangxi and Sichuan strains.The genetic distance of the Shenzhen human serotype 14 strains was close to Guangxi and other cities in Guangdong.A total of 57 virulence genes were detected in S.suis strains in Shenzhen.Statistical analysis showed that 96.97% of human strains were concentrated in the clonal complex 1 group(CC1),CC1 carried more virulence genes than non-CC1.In addition,some pig-derived strains also existed in CC1.Pathogenicity island(PAI)of 89 kb and its variant was found in the human strains.In addition,a serotype 14 S.suis strain containing a 78 kb PAI was isolated from a patient who presented with STSLS and eventually died.Human strains were resistant to tetracycline,streptomycin,erythromycin,and clindamycin,while swine strains were resistant to tetracycline,clindamycin,erythromycin,streptomycin,levofloxacin,and chloramphenicol.In addition,low sensitivity to penicillin was observed in both human and swine strains.A total of 13 drug-resistant genes were detected in human strains,among which the aminoglycoside ant(6)-Ia gene was the most common,followed by the tetracycline tet(O)gene and macrolide-Lincoamine erm(B)gene.A total of 17 drug resistance genes were detected in porcine strains,among which the erm(B)gene was the most common,followed by the tet(O)gene.Conclusions:Human infected with S.suis in Shenzhen may have symptoms such as meningitis,septicemia,and STSLS in severe cases,which seriously endangers people’s health..Therefore,the prevention and control of human infection with S.suis should be strengthened.For people who have close contact with pork,chicken and duck,reasonable and effective health education should be conducted to improve their personal protection awareness and level.At present,S.suis from swine in Vietnam and Guangxi may still have an impact on human infection with S.suis in Shenzhen,suggesting that relevant departments should strengthen the monitoring of S.suis in swine flowing from the above areas.At the same time,citizens should be informed to buy regular channels of pork with quarantine certificates.At the same time,part of the swine flowing into Shenzhen may also have high pathogenicity,which may lead to human infection and disease.Therefore,it is necessary to strengthen the monitoring of virulence genes in the pig strains,to achieve the purpose of prevention beforehand.In addition,the serotype 14 strain containing 78 kb PAI also has the potential to cause death,and its pathogenicity should be further studied.Human S.suis in Shenzhen has serious multi-drug resistance,and the emergence of penicillin intermediate strains should arouse clinical attention and rational drug use. |
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