Study on the carbapenemase genotype and molecular epidemiology of Acinetobacter baumannii / 中华流行病学杂志

<p><b>OBJECTIVE</b>To investigate antibiotic resistance, clonal relatedness and carbapenemase genotype among carbapenem-resistant Acinetobacter baumannii collected from 3 comprehensive hospitals in Ningbo city, Zhejiang province.</p><p><b>METHODS</b>28 strains of carbapenem resistant Acinetobacter baumannii were collected from Ningbo Li Hui-li Hospital, Ningbo Li Hui-li Hospital, Ningbo First Hospital, and N ingbo Second Hospital. The minimum inhibitory concentrations (MIC) of these strains were examined by agar dilution and E-test method. Homology of these isolates was analyzed by pulse-field gel electrophoresis (PFGE) and Genotype of carbapenemases were analyzed by PCR and verified by DNA sequencing.</p><p><b>RESULTS</b>28 strains of Acinetobacter baumanii were highly resistant to all of the antibiotics except polymyxin E. They were classified into 4 clones based on PFGE pattern. Clone A and B had been spreading widely. All of the 28 strains produced carbapenemases which were confirmed as OXA-23 by PCR and sequencing. Metallo-beta-lactamase was not detected in any of the isolates.</p><p><b>CONCLUSION</b>All of t hecarbapenem-resistant Acinetobacter baumannii collected from Ningbo were producing OXA-23 carbapenemase, suggesting that the transmission of clones had occurred in the 3 hospitals.</p>

Genotypes of aminoglycoside-modifying enzyme and clinical study of high-level gentamycin resistant enterococcus / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To determine the antibiotics resistance, aminoglycoside-modifying enzymes and homology of high-level gentamycin resistant enterococcus in clinical specimens.</p><p><b>METHODS</b>The high-level gentamicin resistant (HLGR) isolates were screened by the agar method and the resistance of 14 antimicrobial agents was determined by K-B method. The aminoglycoside-modifying enzyme genes were detected by polymerase chain reaction (PCR). Pulsed-field gel electrophoresis (PFGE) was used to analyze the homology of HLGR isolates.</p><p><b>RESULTS</b>The ratio of HLGR was 64.2% (68/106). Among the HLGR,there were no isolates resistant to linezolid, vancomycin and tecoplanin, and Enterococcus faecium was more resistant to beta-lactam antibiotics and quinolone than Enterococcus faecalis. The positive rate of aac(6')-Ie-aph(2')-Ia was 92.6% and 3 isolates had the resistance gene mostly similar to aph(2')-Id. And among 51 HLGR isolates from the hospitalized patients, PFGE grouped 17 E. faecalis isolates into 4 clusters (A-D), and 33 E. faecium isolates into 8 clusters (A-H) with A cluster as predominant.</p><p><b>CONCLUSION</b>HLGR has become the important antibiotic resistance bacteria which results in nosocomial infection; and aac(6')-Ie-aph(2')-Ia is the main aminoglycoside-modifying enzyme gene which causes HLGR.</p>

Plasmid-mediated carbapenemase KPC-2 in a strain of Klebsieila pneumoniae / 中华检验医学杂志

Objective To investigate the resistant mechanism of imipenem-resistant K. pneumoniae.Methods The minimal inhibitive concentrations (MICs) of the antimicrobial agents were determined by Etest.Isoelectric focusing electrophoresis (IEF),plasmid extraction,conjugation, transformation,PCR amplification,cloning and sequencing were carried out for analyzing the encoding gene of ?-1actamases.Results Three kinds of ?-1actamases were detected with pIs of 7.2,6.7,and 5.4.in a clinical strain of K.pneumoniae.These ?-1actamases were TEM-I (pI,5.4),SHV-12 (pI,8.2) and KPC-2 ( pI,6.7 ) confirmed by sequencing of the PCR products.Only one band of ?-1actamase with pI 6.7 was displayed in the transformant.A 1500 bp segment,which contained the KPC-2 gene confirmed by nucleotide sequence analysis,was cloned from a 60 000 bp plasmid of the transformant.Conclusion The strain of K.pneumoniae resistant to imipenem produces a plasmid-mediated carbapenemase KPC-2 which belongs to Bush group 2f,class A ?-1actamase.