Identification of New Delhi metallo-β-lactamase 1 in Acinetobacter lwoffii of food animal origin.
BACKGROUND
To investigate the presence of metallo-β-lactamase (MBL) genes and the genetic environment of the New Delhi metallo-β-lactamase gene bla(NDM-1) in bacteria of food animal origin.


RESULTS
Gram-negative bacteria with low susceptibility to imipenem (MIC>8 µg/mL) were isolated from swab samples collected from 15 animal farms and one slaughterhouse in eastern China. These bacteria were selected for phenotypic and molecular detection of known MBL genes and antimicrobial susceptibility testing. For the bla(NDM-1) positive isolate, conjugation and transformation experiments were carried out to assess plasmid transfer. Southern blotting was conducted to localize the bla(NDM-1) genes, and DNA sequencing was performed to determine the sequences of bla(NDM-1) and the flanking genes. In total, nine gram-negative bacteria of four different species presented a MBL phenotype. bla(NDM-1) was identified on a mobile plasmid named pAL-01 in an Acinetobacter lwoffii isolate of chicken origin. Transfer of pAL-01 from this isolate to E. coli J53 and JM109 resulted in resistance to multiple β-lactams. Sequence analysis revealed that the bla(NDM-1) gene is attached to an intact insertion element ISAba125, whose right inverted repeat (IR-R) overlaps with the promoter sequence of bla(NDM-1). Thus, insertion of ISAba125 likely enhances the expression of bla(NDM-1).


CONCLUSIONS
The identification of a bla(NDM-1)- carrying strain of A. lwoffii in chickens suggests the potential for zoonotic transmission of bla(NDM-1) and has important implications for food safety.
Key Laboratory of Development and Evaluation of Chemical and Herbal Drugs for Animal Use, College of Veterinary Medicine, China Agricultural University, Beijing, People's Republic of China.
Yang
Y
Wang
Congming
C
Wu
Qijing
Q
Zhang
Jing
J
Qi
Hebing
H
Liu
Yu
Y
Wang
Tao
T
He
Licai
L
Ma
Jing
J
Lai
Zhangqi
Z
Shen
Yuqing
Y
Liu
Jianzhong
J
Shen
D000150:Acinetobacter / Q000187:drug effects / Q000235:genetics*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002645:Chickens / Q000235:genetics / Q000382:microbiology*; D002681:China; D004269:DNA, Bacterial / Q000235:genetics; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D013552:Swine / Q000235:genetics / Q000382:microbiology*; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D015378:Imipenem; D001618:beta-Lactamases; C552864:beta-lactamase NDM-1