Objective       To report a clinical isolated strain of Providencia rettgeri producing New Delhi metallo-β-lactamase (NDM-1)

FR90

and study its   resistance  mechanisms.       Methods       The bacterial strain was progressed with the antimicrobial susceptibility test. Production of metallo-β-lactamase was identified by modified Hodge test. PCR was used to detect several common resistance genes for carbopenemases. Plasmids conjugation

plasmid incompatibility group detection

Pulsed-field gel electrophoresis (PFGE) with S1 nuclease digestion o

f whole genomic DNA (S1-PFGE)

Southern blotting and gene sequencing were conducted to analyze the plasmid characteristics and the surrounding genetic structure of the bla

NDM-1

gene.       Results        Providencia rettgeri FR90 was resistant to quinolone

Polymyxin B

and all β-lactas (including carbapenems) except aztreonam. Modified Hodge test showed it was positive to metallo-β-lactamase. PCR displayed that only the bla

NDM-1

gene was detected among several common resistance genes for carbopenemases. Further study revealed this bla

NDM-1

was located on a broad host-range IncA/C-type conjugative plasmid FR90 in a size of 50 kb

confirmed by S1-PFGE and Southern blotting. A 17-kb fragment from the plasmid was obtained and sequenced

and the bla

NDM-1

gene was flanked by 2 copies of ISAba125

with a downstream gente of trpF

followed by groS

groL and a truncated insE gene.       Conclusion       We report a clinical isolation of NDM-1-producing Providencia rettgeri in the mainland of China

which reminds us to closely monitor the NDM-1-producing bacteria and take infection control measures to prevent the bla

NDM-1

gene spreading among bacteria.