ABSTRACT
Objective To investigate the distribution of acquired carbapenemases in carbapenemresistant strains of Klebsiella pneumoniae, and explore its role in epidemiology of nosocomial infection. Methods From November 2008 to March 2009, twenty clinical isolates of carbapenem-resistant Klebsiella pneumoniae were collected from children hospitalized in Wuhan children's hospital. MICs of antibiotics were tested by DNA of Klebsiella pneumoniae. Modified Hodge test was used to screen strains producing carbapenemases,combined imipenem(IPM)-EDTA , meropenem(MEM)- EDTA and ceftazidime(CAZ) - EDTA double-disk synergy test (DDST) were used to detect metallo-β-lactamase-producing. PCR amplification of the carbapenemase and integrase genes, and sequencing were performed. Plasmid conjugation transfer experiments and Southern hybridization were applied to study the mode of drug resistance transmission. Results Four types of Klebsiella pneumoniae were detected by PFGE, type A consisted of 5 strains, including 3 strains of type Al and 2 strains of type A2), type B (2 strains), type C (12strains) and type D (1 strain). Type A and C were the main drug resistant clones. Eight strains of Klebsiella pneumoniae carried both KPC-2 and IMP-4 genes, 10 strains carried IMP-4 gene, 2 strains carried KPC-2 gene. None of NDM-1 ,GIM, SPM, SIM, OXA-23, and VIM carbapenemase genes was detected in 20 isolates. All of 20 isolates carried lntl which were found to be located on bacterial chromosome by Southern blot. Conclusions KPC-2and IMP-4 genes are the major carbapenemase genes in Klebsiella pneumoniae isolated in Wuhan.Transmission of drug resistance is mainly through vertical transmission of type C resistant clone and horizontal transmission of Intl on bacteria chromosome.
ABSTRACT
Objective To investigate the molecular epidemiology of CRAB isolated from children in wuhan. Methods Forty non-repetitive strains of CRAB were collected from hospitalized children of emergency department, neonatal medicine, cardiothoracic surgery, bone surgery, respiratory medicine and renal medicine in Wuhan children's hospital during December 2008 and May 2009. MIC values were PFGE; KPC, IMP, GIM, SPM, SIM, OXA-23, VIM genes and integrase gene were amplified by PCR and then sequenced to confirm the genotypes.; Plasmid conjugation experiment was used to study the transfer method of bacterial resistance and southern blot hybridization was used to target the resistance genes. Results Susceptible rates of 40 strains to gentamicin, tobramycin, amikacin, ciprofloxacin, levofloxacin, trimoxazole were 20%, 5%, 93%, 93%, 95%, and 23% respectively. Eleven types of clone were detected by PFGE,including 29 strains of type A clone, 2 strains of type B clone, and 1 strain for each type of C to K clone. Eleven isolates produced both IMP-4 and OXA-23 carbapemase. Twenty-six isolates only possessed OXA-23 carbapemase. Thirty-six strains carried class Ⅰ integron. The results of southern blot hybridization showed that Intl, IMP-4 and OXA-23 type were located on chromosome. Conclusions Type A clone of CRAB is the most common. OXA-23 and IMP-4 type are the major acquired carbapemases, especially the OXA-23 is the most common type. The horizontal transmission of OXA-23 and IMP-4 gene mediated by Int1 and the spread of type A resistant clone is the major way of the spread of carbapenem-resistant Acinetobacter baumannii in the region.