Distinct Antimicrobial Resistance Patterns And Heterogeneity Of β-Lactamases In Clinical Chryseobacterium Spp.

ObjectiveTo determine the distribution of antimicrobial resistance and heterogeneity ofβ-lactamases in clinical Chryseobacterium spp..Materials and MethodsIsolatesFifty-two Clinically-isolated Chryseobacterium spp.were collected from March 2004 to December 2006 at the First Affiliated Hospital of Anhui Medical University,a 1500-bed public tertiary-care teaching hospital in Hefei,China.The majority of Chryseobacterium spp.were either C.indologenes or C.meningosepticum.MethodsThe MIC of 18 antimicrobial agents to 52 Chryseobacterium spp.strains was detected by agar dilution method.Phenotype ofβ-lactamases was detected by three-disc synergy test and modified three dimension test.polymerase chain reaction(PCR) amplification with some prime sets for bothβ-lactamases and integrase gene was conducted for all isolates. PCR amplification for complete coding gene ofβ-lactamases was conducted,and then the DNA sequence analysis was conducted for the amplified which are positive forβ-lactamases identified in Genotype analysis.Conjugation experiment was used to study the transmission ofβ-lactamases encoding gene.pIs ofβ-lactamases were measured by isoelectric focusing assayResultsIn an antimicrobial susceptibility test,most strains of 52 Chryseobacterium spp.were resistant to piperacillin,imipenem,meropenem,cefotaxime,aztreonam and ceftazidime, showing resistance rates of more than 40%.Significantly,38(73.1%) were resistant to imipenem and meropenem.However,gatifloxacin,levofloxacin and rifampin had better antimicrobiotial ability to Chryseobacterium spp.compared with other antimicrobial agents in MIC.PCR identified that 20 C.indologenes isolates were confirmed to be carrying an bla_IND gene and none had other MBLs genes,including 9 bla_IND-1-carrying isolates,10 bla_IND-2-carrying C.indologenes and 1 had bla_IND-3 alleles.Interestingly,Of the twenty MBLs-carrying isolates,19 were found to be positive in two phenotypic MBLs detection methods,with one C.indologenes isolate(C-15) giving a negative result with both modified three dimension test and disk synergy test.14 C.meningosepticum strains were detected to have MBLs genotype by PCR amplification using prime sets of complete coding gene,including 15 blaB and 2 blaGOB. The number of blaB,blaB₂,blaB₃,blaB₁₁,blaGOB-1 and blaGOB-10 was 2,5,4,4,1 and 1 respectively.7 C.meningosepticum were detected to have ESBLs,Among them,3 strains were detected to have blaCME-1 genotype and 4 strains to have blaCME-2 genotype.The ratio of AmpC producing in Chryseobacterium spp.was 0.0%.repeated attempts to transfer theβ- lactamases gene by conjugation failed.Plasmids were extracted in 4 Chryseobacterium spp.strains but none of them harborβ- lactamases gene.ConclusionChryseobacterium spp.have high multi-drug resistance,especially highly resistant to imipenem and meropenem and thus it is difficult to therapy.C.meningosepticum could produce MBLs and ESBLs simultaneously and have high percentage ofβ-lactamase producing.C.indologenes have high rate of MBLs producing.The majority of bla_IND-producers isolated from this area had either bla_IND-1 or bla_IND-2.