Molecular Characteristics And Antibiotical Susceptibility Of Methicillin-resistant Staphylococcus Aureus Isolated From Chinese Children

Objects:Studies from around the world report that the characteristics ofhospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) arechanging because of the invasion of community-associated MRSA (CA-MRSA).New challenges are brought to MRSA in terms of prevention,controling transmitionand clinical treatment.This study aims to evaluate the molecular characteristics andantibiotic susceptibility of HA-MRSA isolated from Chinese children.Methods:A total of264MRSA are collected from children in8hospitals from2008to2011.According to the American Centers for Diseases Control and Prevention(CDC),106MRSA are claddified as HA-MRSA.All isolates were analyzed bymultilocus sequence typing (MLST), staphylococcal cassette chromosome mec(SCCmec) typing, staphylococcus protein A (spa) typing, and prevalent clone areanalyzed by pulsed-field gel electrophoresis (PFGE). Panton-Valentine leukocidingene (pvl) and plasmid analysis are also detected.Results: Among the106HA-MRSA collected,the commonest diseases arepneumonia（41/106,38.7%） and skin and soft tissue infections(SSTIs)（19/106,17.9%）15ST types are detected, ST239(53/106,50.0%),followed byST59（24/106,22.6%）、ST5(7/106，6.7%),ST88(5/106，4.7%), ST25、ST7、ST1801、ST509、ST960、ST338、ST398、ST375、ST93、ST72、ST9(less than3.0%,respectively).The most prevalent clone was ST239-SCCmec III (50/106,47.2%)，followed by ST59（24/106,22.6%）and others. Up to36.8%of isolates (ST59 （24/106,22.6%）, ST5(7/106,6.7%), ST88(5/106,4.7%), and2.8%ST72(3/106,2.8%))from children with hospital-associated infections were CA-MRSA genotypes.27PFGE types and5PFGE subtybes were found in ST239,22PFGE types and no PFGEdubtypes were found in ST59.23.6%(21/106) of the isolates were positive forpvl.87.5%ST59were positive for pvl.The antibiotic resistances to penicillin,azithromycin, erythromycin, tetracycline,cefuroxime, clindamycin, gentamicin,rifampin, telithromycin, ciprofloxacin,trimethoprim-sulfamethoxazole,chloramphenicol, tigecycline, fusidic acid, mupirocin,dalfopristin were98.1%,86.8%,81.1%,77.4%,74.5%,67.0%,55.7%,45.3%,45.3%,42.5%,15.1%,7.5%,2.8%,0.9%,0.9%, and0.9%, respectively. In addition, all isolateswere sensitive tovancomycin and linezolidST239were more resistant to cefuroxime (P<0.05),gentamicin (P<0.05), tetracycline (P<0.05), trimethoprim-sulfamethoxazole (P<0.05),rifampin (P<0.05), ciprofloxacin (P<0.05), and telithrimycin (P<0.05) than ST59, andwere more sensitive to erythromycin (P<0.05), clindamycin (P<0.05), andazithromycin (P<0.05) than HA-MRSA-ST59.61.3%of HA-MRSAcarried plasmids.The most prevalent pattern carried a plasmid of more than23kb (25/65,38.5%).Neonates infected with25%strains of ST59and3.8%of ST239(p＜0.05). Invasiveinfections were caused by37.5%strains of ST59and18.8%of ST239MRSA.Conclusions: The genomic background of HA-MRSA in Chinese children is diverse.Strains with CA-MRSA genotypes were detected, and the most prevalent were ST59isolates which were with a high carriage rate of pvl gene and plasmid more than23kb,were more common to infect neonates and more likely to cause invasive infections. Objective: The present study aimed to investigate the molecular characteristics andantimicrobial susceptibility of community-associated methicillin-resistantStaphylococcus aureus (CA-MRSA) isolates from children with skin and soft tissueinfections (SSTIs).Methods: A total of60CA-MRSA isolates were collected from children with SSTIs.The clinical data were recorded. The multilocus sequence typing(MLST) andstaphylococcal cassette chromosome mec (SCCmec) types were analyzed bymultiplex polymerase chain reaction (PCR). The spa type was also analyzed by PCR.The Panton–Valentine leukocidin (PVL) gene was detected. The antimicrobialsusceptibility was determined with15antibiotics.Results: Among60SSTI cases, the most common form of the disease was abscess(n=25,41.7%), followed by impetigo(n=12,20%). Twelve ST types wereidentified.The most common type was ST59(n=29,48.3%), followed by ST88andST1(6each,10.0%).Four SCCmec types were found. The most common type wasSCCmecIV (55.5%,33/60), followed by SCCmecV (28.3%,17/60), SCCmecIII(15.0%,9/60), and SCCmecII (1.7%,1/60). Amongthe21spa types, the mostcommon was t437(46.7%). The prevalence of PVL was50%in the CA-MRSAstrains tested. The percentage of the CA-MRSA strains resistant to erythromycin,clindamycin, gentamycin, chloramphenicol, tetracycline, ciprofloxacin,trimethoprim-sulfamethoxazole, rifampin, fusidic, and mupirocin were90.0%,80.0%, 46.7%,38.3%,38.3%,33.3%,28.3%,11.6%,3.3%, and3.3%, respectively. Theprevalence of multidrug resistant strains was73.3%.Conclusion: The most frequently isolated bacterial clones wereMRSA-ST59-SCCmecIVa-t437and MRSA-ST59-SCCmecV-t437in the childrenwith SSTIs caused by CA-MRSA. The multidrug resistant strains was highlyprevalent. Erythromycin and clindamycin should not be preferred in empirictreatment of children with community-acquired SSTIs.