Distribution of a transposon-like element carrying bla(CMY-2) among Salmonella and other Enterobacteriaceae.
OBJECTIVE
The dissemination of cephamycin resistance in Enterobacteriaceae and its correlation with a transposon-like DNA element consisting of a specific tnpA-bla(CMY-2)-blc-sugE structure were investigated.


METHODS
A total of 140 enterobacterial isolates belonging to 17 species (10 genera) of Enterobacteriaceae phenotypically characterized as putative AmpC-producers were evaluated. The isolates were examined by PCR analysis, DNA-DNA hybridization and nucleotide sequencing.


RESULTS
The bla(CMY-2)-carrying element was detected in 34 isolates from 10 species (9 genera), including all 14 Salmonella and 4 Shigella isolates as well as 7 of the 10 Escherichia coli isolates tested. The remaining 9 isolates were from 112 isolates of the other 14 species tested. The genetic structure of the bla(CMY-2)-carrying element was identical in 29 isolates, while in 3 E. coli and 2 Citrobacter isolates an additional insertion sequence IS1 was found inserted at various nucleotide positions close to the 3' end, either within or downstream, of tnpA. In 12 of the 14 representative isolates examined, the bla(CMY-2)-carrying element was found inserted in the finQ gene of various-sized plasmids with highly conserved 8 bp direct repeats flanking the junction regions. Among the other 106 non-CMY-2-producing isolates, plasmid-mediated ampC genes were found only in one isolate of Enterobacter aerogenes which carried a bla(DHA-1)-like gene.


CONCLUSIONS
bla(CMY-2) is the most prevalent plasmid-mediated ampC gene among Enterobacteriaceae. All the bla(CMY-2) genes identified in the present study were associated with a specific transposon-like element that may be responsible for the spread of bla(CMY-2) among Enterobacteriaceae.
Su
Lin-Hui
LH
Department of Clinical Pathology, Chang Gung Memorial Hospital, 5 Fu-Hsin Street, Kweishan, Taoyuan 333, Taiwan.
Chen
Hsiu-Ling
HL
Chia
Ju-Hsin
JH
Liu
Shu-Ying
SY
Chu
Chishih
C
Wu
Tsu-Lan
TL
Chiu
Cheng-Hsun
CH
D018550:Cephalosporin Resistance / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial; D004755:Enterobacteriaceae / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D012475:Salmonella / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D001618:beta-Lactamases / Q000235:genetics*
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C103022:beta-lactamase CMY-2; D001618:beta-Lactamases