The Clinical Isolated Of Community Acquired Methicillin-resistant Staphylococcus Aureus With Genetic Analysis

Staphylococcus aureus is a clinical significant pathogenic bacteria. Methicillin-resistant Staphylococcus aureus(MRSA)increases the case fatality rate of infectious disease by Staphylococcus aureus.It becomes a major pathogen of hospital onset of infection.From the last end of the century,Community acquired methicillin-resistant Staphylococcus aureus(CA—MRSA)was reported one after another.Object:To investigate genetic characteristic of CA-MRSA in Tianjin.Include as follows:detect their drug sensitivity,investigate the information of carrying pvl gene, typing by SCCmec and MLST.Method:1.Strains' collection and their drug sensitivity:Collect staphylococcus aureus from four hospitals in Tianjin during 2001 to 2006.15 of all are Staphylococcus aureus Nasal Carriage;125 of all are clinical strains.According to the concept of CA-MRSA,the clinical strains are classified HA-MRSA and CA-MRSA.screening MRSA by disc agar diffusion method with cefoxitin.Through broth dilution method, detect their MIC for 12 antibiotics,(including:penicillin,oxacillin,ampicillin, ciprofloxacin,moxifloxacin,cefazolin,chlormycetin,lincomycin,gentamycin, ceftriaxone,vancomycin and erythromycin).Analyze their drug tolerance ratio.2.Screening for pvl gene:By PCR method,detect all strain for pvl gene.Then, Carry out DNA sequence analysis of PCR's product.3.Typing by SCCmec:Reference Olivera's study and synthetic primer. Through multiplex PCR assay,typing HA-MRSA and CA-MRSA by SCCmec.4.Typing by MLST:amplify seven house-keeping gene,and carry out DNA sequence analysis of PCR's product.Send analytic result to database's network (http://saureus.mlst.net).Get the strain's sequence type.Result:1.Screening MRSA:Among 132 Nasal Carriage of health people,obtain 15 staphylococcus aureus strains.The nasal carriage ratio is 11.36%.By disc agar diffusion method with cefoxitin,they are all MSSA.No MRSA was found among health people.There are 54 MRSA in 125 clinical strains,12 is CA-MRSA and 42 is HA-MRSA.Through broth dilution method,detect their MIC for 12 antibiotics. There are high drug tolerance ratios to 11 antibiotics except vancomycin,among 42 HA-MRSA.It shows multi-resistant feature.And,among 12 CA-MRSA,there are low drug tolerance ratios to nonβ-lactam antibiotics exceptβ-lactam antibiotics. There are high drug tolerance ratios to penicillin and middle drug tolerance ratios to lincomycin and erythromycin among 15 Nasal Carriage.They are sensitive to other antibiotics.2.Detect pvl gene by PCR:In 125 clinical strains and 15 Nasal Carriage strains, detect pvl gene.Only 3 strains carry pvl gene.There is low carriage ratio for pvl gene (3/140).One belongs to CA-MRSA.It's from pus.The other belong to MSSA from sputum.3.Typing by SCCmec:typing 42 HA-MRSA and 12 CA-MRSA through multiplex PCR assay by SCCmec.Among 12 CA-MRSA,they all belong to SCCmecⅣexcept one belong to unknow type.Among 42 HA-MRSA,there are more SCCmecⅢand SCCmecⅢa strains,10 and 16 strains,respectively.Otherwise,7 belong to SCCmecⅡ,and 6 belong to SCCmecⅢb.3 strains belong to unknow type.No SCCmecⅠstrain was found.4.Typing by MLST:typing one CA-MRSA carried pvl gene,namely 6Saul,by MLST.It belongs to ST88 from pus.Conclusion:1.No CA-MRSA was found among health people Nasal Carriage.There 12 CA-MRSA in 54 MRSA.2.Through drug sensitivity test,pvl gene by PCR,SCCmec typing and MLST, analysis 12 CA-MRSA.One carried pvl gene belongs to SCCmecⅣ.It's ST88 by MLST.Moreover,11 CA-MRSA don't carry pvl gene,and they all belong to SCCmecⅣexcept one strain.It is coincidence with reports abroad.This study is first and systemic investigation for epidemic,clinical feature and gene typing of CA-MRSA,by genetic analysis method,in Tianjin.