No abstract

A novel dextransucrase gene, DSRN, was obtained by ultrasoft X-ray treatment of the DSRB742 gene. The DSRN gene was further mutated via site-directed mutagenesis producing four mutants: DSRN1 (F196S), DSRN2 (Y346N), DSRN3 (K395T) and DSRN4 (P980T). Dextransucrases derived from DSRB742 and its mutants were expressed in E. coli and affinity-purified using dextran to give 80% purity. They had specific activities of 0.6-17 U/mg with Km values of 18-88 mM. DSRB742 had the lowest (0.02 s(-1) x mM(-1)) and DSRN1 had the highest (0.13 s(-1) x mM(-1)) Kcat/Km values. DSRN3 had the highest enzymatic transglycosylation efficiency with maltose (63% of theoretical), gentiobiose (39%), or salicine (40%).

A total of 114 Acinetobacter sp. isolates were collected from patients in the emergency departments (EDs) of two Korean hospitals. Most isolates belonged to the Acinetobacter baumannii complex (105 isolates, 92.1 %). Imipenem resistance was found in 39 isolates (34.2 %) of the Acinetobacter sp. isolates, and 6 colistin-resistant isolates were also identified. Species distribution and antimicrobial-resistance rates were different between the two hospitals. In addition, two main clones were identified in the imipenem-resistant A. baumannii isolates from hospital B, but very diverse and novel genotypes were found in those from hospital A. Many Acinetobacter sp. isolates, including the imipenem-resistant A. baumannii, are considered to be associated with the community. The evidence of high antimicrobial resistance and different features in these Acinetobacter sp. isolates between the two EDs suggests the need for continuous testing to monitor changes in epidemiology.