OBJECTIVE

To learn Molecular characterization of metallo beta-lactamase (MBL) found in a clinical isolate of Stenotrophomonas maltophilia and confirm the role of MBL played in the antimicrobial-resistance of S. maltophilia by sequencing the encoding genes of the metallo beta-lactamase and construct the prokaryotic expression vector carrying the MBL gene and expressed in E. coli BL21.

METHODS

The blaMBL gene was amplified by PCR and cloned into pMD18-T plasmid. The recombination was subcloned into pET32a+ plasmid and expressed in E. coli BL21. The susceptibility between expression vectors and strain 750 to antibiotics were compared.

RESULTS

The 867 bp DNA fragment of MBL encoding gene was amplified from the strain 750 by PCR and sequenced. The gene was 99.31% homologous to blaS and blaL1 of MBL L1. After being transformed into the E. coli BL21 and induced with lmM IPTG, a recombinant protein of about 48 kDa was expressed in the pET32a+-blaMBL system. The susceptibility of pET32a+-blaMBL system and strain 750 showed MIC 12 mg/L and 128 mg/L to imipenem and MIC 2 mg/L and 2 mg/L to ceftazidime, respectively.

CONCLUSION

The MBL produced by strain 750 was similar to the that in strain ULA511. The difference of MIC to imipenem between wild strain and E. coli BL21 transformant indicated that other unclear mechanism involving in imipenem resistance in the strain.