Bacterial distribution and antibiotic resistance analysis during 2012

Objective To investigate the distribution and antimicrobial resistance of clinical bacterial isolates in 2012.Methods Strains were isolated and identified using conventional methods.Antimicrobial susceptibility testing was carried out using Kirby-Bauer method.The minimum inhibitory concentrations(MICs)of vancomycin for Staphylococcus spp.and penicillin for S. pneumoniae were determined by E-test.Results were interpreted according to the breakpoints of CLSI 2012.All data were analyzed by WHONET5.5 software.Results A total of 4 454 nonduplicate clinical isolates were collected during 2012,including gram negative bacteria(3 181,71.4%)and gram positive bacteria(1 273,28.6%).The main source of these pathogens was respiratory specimens(28.5%),followed by blood(26.7%)and pus(including wound secretion,20.3%).The top five pathogenic bacteria were E.coli,A.baumannii,P.aeruginosa,K.pneumoniae and S.aureus,accounting for 16.1%,12.4%, 11.8%,10.3%and 8.8%,respectively.The prevalence of MRSA in S.aureus and MRCNS in coagulase-negative Staphylococcus was 29.2%and79.0%,respectively.No staphylococcal strain was found resistant to vancomycin,teicoplanin or linezolid.The prevalence of penicillin-resistant S.pneumoniae was 14.2%in non-cerebrospinal fluid.The beta-hemolytic Streptococcus strains showed higher resistance rates to eythromycin and clindamycin.E.faeciumstrains showed much higher resistance rates to most antibiotics tested than E.faecalis.Vancomycin resistance was found in 2 E.faeciumstrains and 4 E.faecalis strains.The prevalence of ESBLs was 68.0% in E.coli, 40.4%in Klebsiellaspp.(K.pneumoniae and K.oxytoca) and 34.0%in P.mirabilis.ESBLs-producing strains were more resistant to most antibiotics than non-ESBLs-producing strains.Less than 10.0% of the Enterobacteriaceae strains were resistant to imipenem or meropenem.Imipenem resistance was found in20.2%of the P.aeruginosaisolates.More than 60% of the A.baumannii strains were resistant to all the antibiotics tested except cefoperazone-sulbactam.Conclusions Antibiotic resistance is serious in the clinical bacterial isolates in our hospital during 2012,especially,the rapidly increasing resistance level of A.baumannii to carbapenems,which is a clinical concern.