Molecular Characteristics Of Community-acquired Staphylococcus Aureus Associate With Skin And Soft Tissue Infections

Objective1.We retrospectively analyzed drug resistance rates and virulence profiles of community-acquired Staphylococcus aureus(S.aureus)causing skin and soft tissue infections(SSTIs)in Quzhou,and provided guidance for clinical antibiotic use.2.To explore and analyze the molecular characteristics and virulence profiles of community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA)isolated from SSTIs in Quzhou.3.We performed a whole-gene sequencing analysis towards the new sequence type ST5423 and compared with SR434 ST88,focusing on virulence and drug resistance genes.Methods1.We retrospectively analyzed Staphylococcus aureus isolated from SSTIs in Quzhou People's Hospital from 2014 to 2018,and screened out community-acquired infection samples to detect drug sensitivity and virulence genes carrying.2.We use multilocus sequence typing(MLST)analyzed the molecular characteristics of CA-MRSA strains.3.Whole-genome sequencing of the newly discovered sequence type ST5423 was performed on the Illumina Hi Seq X-ten platform.Use Shovill for splicing after sequencing.We use RAST(website https://rast.nmpdr.org/)for gene annotation,and CGE(website http://www.genomicepidemiology.org/)for virulence and resistance genes screening.Results1.A total of 246 community-acquired S.aureus causing SSTIs were screened,of which CA-MRSA account for(29.27%,72/246).The separation rates of CA-MRSA causing SSTIs is increasing year by year,from 23.08% in 2014 to 39.02% in 2018.The vast majority of isolates(226/246,91.87%)were resistant to penicillin and(148/246,60.16%)to erythromycin.CA-MRSA strains have high resistance rates to erythromycin(90.28%,65/72),clindamycin(68.06%,49/72),and tetracycline(41.67%,30/72).We have not detected vancomycin,nitrofurantoin,linezolid,and daptomycin resistant strains.The resistance rates of CA-MRSA strains to erythromycin,clindamycin,tetracycline and penicillin were significantly higher than that of methicillin-susceptible Staphylococcus aureus(MSSA)(P <0.05).The positive rates of virulence genes among all S.aureus as follows,hla(233/246,94.72%),hlb(58/246,23.58%),PVL(99/246,40.24%),fnb A(135/246,54.88%),fnb B(112/246,45.53%),sec(15/246,6.10%),seh(9/246,3.66%).Compared with MSSA,CA-MRSA had higher PVL and hlb gene carrying rates(P <0.05).2.ST59 is the main epidemic strain of SSTIs CA-MRSA,accounting for(55.56%,40/72).The majority ST59 CA-MRSA clones were resistant to clindamycin(85.00%,34/40),erythromycin(87.50%,35/40),tetracycline(42.50%,17/40).The resistance rate of ST59 to clindamycin were significantly higher than that of other sequence types(P <0.05).The frequency of carriage for PVL among ST59 isolates was significantly higher than that for non-ST59 isolates(P <0.05).3.ST5423 and SR434 all carry exoenzyme genes such as aur,spl A,spl B,hostimm genes like sak,scn,toxin genes like hlg A,hlg B,hlg C,Luk D,Luk E,and resistance genes lnu A,bla Z,mec A,and erm C.However,ST5423 were positive for PVL gene and SR434 was negative for PVL gene.There were more enterotoxin genes sec,sel,sea/sep detected in SR434,and only one enterotoxin gene was sep in ST5423.A gene dfr G that mediates resistance to trimethoprim-sulfamethoxazole was detected in ST5423,but was not carried in SR434.But SR434 carries fosmycin resistance gene fos B.ST5423 were resistant to cefoxitin,penicillin,and erythromycin.QZ04 and QZ06 are resistant to trimethoprim-sulfamethoxazole.Conclusions1.The community-acquired S.aureus isolated from SSTIs in Quzhou area have high resistance rates to penicillin and erythromycin,and should not be used as the first choice in clinical experience.The following antibiotics can be used for empirical treatment,such as quinolones,compound sulfamethoxazole,vancomycin.2.The detection rates of CA-MRSA SSTIs in Quzhou area were high,and there is a rising trend year by year.CA-MRSA strains have high resistance rates to erythromycin,clindamycin,tetracycline and penicillin.These antibiotics are not recommended.The resistance rate to trimethoprim-sulfamethoxazole and most fluoroquinolones is less than 10%.It is sensitive to vancomycin,daptomycin,linezolid.These antibiotics can be used in clinical treatment.3.The main epidemic strain of SSTIs CA-MRSA in Quzhou is ST59,which is consistent with other regions in China.The PVL carrier rates of ST59 isolates were significantly higher than other isolates.4.The four strains of ST5423 are highly consistent and appear to have stronger virulence and broader-spectrum drug resistance,and whether they will cause widespread epidemics requires further monitoring.