Association of the extended-spectrum lactamase blaTLA1 gene to a novel ISCR element, ISCR20
Abstract number: P692
Objective: TLA-1 is an Ambler class A extended-spectrum b-lactamase reported from an Escherichia coli R170 clinical isolate described from Mexico City in 2000. The aim of the study was to characterize the genetic elements associated with of the blaTLA-1 gene from E. coli R170 and from a collection of TLA-1-producing Enterobacteriaceae recovered from various hospitals from Mexico City.
Methods: The 150-kb plasmid RZA92 (pRZA92) of E. coli R170 was extracted by using the Qiafilter Maxi plasmid purification kit and sequenced. The blaTLA-1 gene initiation site of transcription was mapped using a 5' rapid amplification of cDNA ends PCR technique. TLA-1-producing enterobacterial isolates were typed by the PFGE technique. Plasmids were transferred by conjugation to azide-resistant E. coli J53 strain. Plasmids were extracted from the tranconjugants by the Kieser technique, transferred and hybridized with a TLA-1 probe. Their incompatibility group (Inc) were determined by PCR.
Results: Analysis of the nucleotide sequence (5,925 bp) of pRZA92 surrounding the blaTLA-1 gene did not contain any insertion sequence forming a transposon or any class 1 integron structure but evidenced a novel ISCR element, ISCR20, coding a 406 amino-acids transposase. A third of the transposase has respectively 33%, 30% and 27% of identity with that of the ISCR1, ISCR2 and ISCR3. This element is inserted 232 bp upstream of the initiation start codon of the blaTLA-1 gene and brings it its own promoter. An open reading frame (orf) encoding a methyl-accepting chemotaxis protein element, but no ISCR20 element, was evidenced upstream of the blaTLA-1 gene. An orf encoding a reverse transcriptase/maturase (group II intron) preceded the ISCR20 element. After PFGE analysis, eight non-clonal clinical isolates TLA-1-producing Enterobacteriaceae were identified. For seven isolates, the blaTLA-1 gene was located on conjugative plasmids of various sizes (ca. 110 kb to 150 kb) belonging to various group of incompatibility (IncA/C, IncF, IncL/M or IncN). The blaTLA-1 gene was transferred from the seven isolates to E. coli J53 by conjugation. The same ISCR20 element was identified upstream of the blaTLA-1 genes in seven isolates.
Conclusion: The transposase encoded by the ISCR element may transpose an adjacent DNA via a rolling-circle (RC) transposition mechanism. Our study highlights a novel element, ISCR20, which is involved in the expression of the blaTLA-1 gene and may allow its transfer.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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