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Objective:To investigate the relationship of pks gene islands with virulence genes, capsular serotypes and biofilm formation in Klebsiella pneumoniae ( Kp). Methods:A total of 113 Kp clinical isolates were collected in the First Affiliated Hospital of Fujian Medical University and divided into two groups based on the presence of pks gene islands: pks+ and pks- groups. The hypermucoviscous (HM) phenotype was detected by string test. Five virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and six common capsular serotypes (K1, K2, K5, K20, K54, K57) were detected by polymerase chain reaction (PCR). The biofilm formation ability was measured by crystal violet staining. Results:Among the 113 Kp isolates, 46 were pks+ strains and 67 were pks- strains. The detection rate of HM phenotype was higher in the pks+ group than in the pks- group [87.0% (40/46) vs 43.3% (29/67)]. The detection rates of virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and K1 serotype in the pks+ group were also higher than those in the pks- group ( P<0.05). The biofilm formation ability of the pks+ strains was higher than the pks- strains ( P<0.05). Conclusions:Kp strains carrying pks gene islands were likely to display a HM phenotype and mainly belonged to the K1 serotype. Most of the pks+Kp strains carried the virulence genes of peg-344, rmpA, rmpA2, iucA and iroB, and had a greater ability to form biofilms.
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Objective:To provide a promising and optimal laboratory susceptibility-testing method for the clinical usage of antibiotic (polymyxin), four susceptibility-testing methods were performed and the broth microdilution (BMD) was chosen as the gold standard.Methods:A total number of eighty-eight nonduplicate clinical Enterobacteriaceae specimes were collected from January to December of 2019 in the First Affiliated Hospital, Fujian Medical University. Among the clinical specimens, of which six strains were positive for mcr-1. The minimal inhibitory concentration (MIC) of polymyxin of the clinical specimens were examined by the following methods: (1) broth microdilution, (2) colistin broth disk elution, (3) Vitek-2?, (4)BD PhoenixTM,(5)commercial broth microdilution. With BMD as reference, essential agreement (EA), categorical agreement(CA), very major error(VME) and major error (ME) of polymyxins for different methods were analyzed. The Kappa-consistency testing, paired Chi-square testing and the Spearman-rank correlation testing were used to analyze the consistency between the four antimicrobial susceptibility testing methods and the gold standard.Results:Taking broth microdilution as reference, the EA of colistin broth disk elution, Vitek-2?, BD PhoenixTM, commercial broth microdilution were 94.32% (83/88), 92.05% (81/88), 90.90% (80/88), and 96.59%(85/88), respectively. The CA of all the four methods were 100% (88/88). No VME and ME were recorded for four methods. Moreover, the consistency between four susceptibility testing methods and the gold standard is acceptable (Kappa values=1, P<0.001, McNemar test P=1 and r>0.5, P<0.05). Conclusions:In the present work, four susceptibility testing methods all met the standards recommended jointly by the Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing, of which the performance of the commercial broth microdilution and CBDE fared relatively well. Thus, these four methods could be routinely used in clinical microbiology laboratory of our hospital for colistin and polymyxin B susceptibility testing.