Molecular Typing And Antimicrobial Resistances Of Methicillin-Resistant Staphylococcus Aureus

Objective To study the distribution of PLV virulence factors of MRSA strains isolated from three hospitals in Quanzhou(the Second Affiliated Hospital of Fujian Medical University,the Children’s Hospital of Quanzhou,and the Jinjiang municipal Hospital),detect spa typing,MLST typing and SCCmec typing and,perform antibiotic susceptibility testing,so as to make clear the virulence factors,molecular characteristics and antibiotic resistance phenotype.Methods the PVL gene was detected by simple PCR and the results were observed by agarose gel electrophoresis;The X polymorphic region of Protein A of Staphylococcus aureus was amplified by simple PCR,and the target gene fragments were sequenced in order to obtain multiple sets of 24 bp repeats.The sequence comparison was performed at www.ridom.de/spaserver/ to obtain spa types;SCCmec typing of 65 MRSA isolates was performed using multiplex PCR;The 7 housekeeping genes of S.aureus were amplified and sequenced.Sequence alignment was performed using the MLST website(http://saureus.mlst.net)to generate sequence clones.The e BRUST software was used to generate cloned complexes(CC)and analyze the correlation between various types.Antibiogram testing of the MRSA isolates was performed by Vitek Microbial Analysis Instrument,and analyzed the antibiotic resistance according to the CLSI 2017 standards.Results Among 65 MRSA clinical isolates,31 were PVL positive and 34 were negative,the positive rate is 47.7%.MRSA major clone types of molecular typing: CC59-ST59/ST338 clones were the main clones in Quanzhou,a total of 38 strains,accounting for 58.5%(38/65),of which CC59-ST59/ST338-spa t437-IV a total of 28 strains,accounting for 43.1%(28/65)and the CC59-ST59/ST338-spa t437-III6 strains,accounting for 9.2%(6/65),the two clone types totaled 34 strains,accounting for 52.3%(34/65).There were 6 CC8-ST239-spa t030-III/IV isolates,accounting for 9.2%(6/65).There were 4 CC5-ST5/ST965-spa t060/t062-IV isolates,accounting for 6.1%(4/65).Results of antimicrobial susceptibility test: penicillin-resistant rate was 100%;No resistance to teicoplanin,linezolid,and vancomycin;The drug resistance rates to ciprofloxacin,compound sulfamethoxazole,gentamicin,levofloxacin,clindamycin,erythromycin,rifampin,and tetracycline were 15.4%,12.3%,12.3%,13.9%,87.7%,86.2%,6.2%,36.9%,respectively.The multi-resistance rate of MRSA was 93.8%(61/65),and the resistance patterns were mainly DA/E and DA/E/TE patterns,accounting for 46.2%(30/65)and 24.6%(16/65)respectively.Conclusions In the three hospitals in Quanzhou,the detection rate of PVL virulence factors was high,suggesting a high pathogenic risk of MRSA infection.The cross-infection of CA-MRSA and HA-MRSA was presented,the molecular characteristics were increasingly blurred,HA-MRSA with typical CA-MRSA molecular characteristics(SCCmec type IV,V type,and PVL positive)had become an important cause of healthcare-related infections.CC59-ST59/ST338-spa t437-IV(43.1%)was the main clone type in Quanzhou,followed by CC59-ST59/ST338-spa t437-III and ST239-spa t030-IV/III each 9.2%(6/65).MRSA multiple resistance rate was very serious.No MRSA strains is resistant to vancomycin,linezolid and teicoplanin.