Characterization Of NDM-1Producing Acinetobacter Baumannii

NDM-1is a newly-described metallo-beta-lactamase (MBL) encoded by blaNDM-1, firstly identified in single isolate from a patient repatriated to Sweden after treatment in a hospital in New Delhi, India. So it is called’New Delhi metallo-beta-lactamase1’with the western scholars. This bacteria with blaNDM-1is resistant to beta-lactam antibiotics and carbapenems, such as penicillin, cephalosporin. But it is susceptible to quinolone and aminoglycoside antibiotics. So the therapeutic options for infections caused by these organisms are very limited.The strain employed in this study, NDM-1producing Acinetobacter baumannii, derived from the sputum culture of a lung cancer patient of Xiamen. The biological and morphological characteristics of NDM-1producing Acinetobacter baumannii analyzed by gram staining, electro-microscope observation, susceptibility test and PCR.Gene blaNDM-1of NDM-1producing Acinetobacter baumannii was identified and amplified by PCR. blaDM-1was cloned into plasmid vector pMD18-T and then transferred into E. coli DH5a recipient by transformation. Sequence analysis of blaNDM-1encoding the metallo-beta-lactamase indicated that there was a24bp insert sequence between blaNDM-1and trpF, compared with that of K. pneumoniae KP-05-506from India. Minimum inhibitory concentration (MIC) of the recombination strain DH5a (pMD18-T::blaNDM-1) was increased256times than DH5a to meropenem.The NDM-1gene is carried on plasmid in mostly. So we studied the plasmid of NDM-1producing Acinetobacter baumannii, including the plasmid extraction and elimination. The result showed that the NDM-1gene was carried on plasmid of NDM-1producing Acinetobacter baumannii, and Nalidixic Acid and SDS were effectively eliminated the plasmid from the strain. The strain without the plasmid was lost resistant to beta-lactam antibiotics and carbapenems.According to the previous report, the patient that was traveling in India, was colonised by K pneumoniae and Escherichia coli with blaNDM-1on plasmids of varying size, which readily transferred between bacterial strains in vitro. So we studied conjugation between the donor NDM-1producing Acinetobacter baumannii and the recipient DH5a (pBR322) with a tetracycline resistance. The result showed that the NDM-1gene could transferred to DH5a:: pBR322either in vitro or in vivo of mice.For the non-beta-lactam antibiotics, an identical resistance profile was shared by all the transconjugants. At present, this mobile elements carried on the broad resistance has received extensive attention from all over the world. Overall, this study laid a foundation for the horizontal resistance gene transfer through mobile elements.