Diversity of CTX-M gene environments in Escherichia coli and Klebsiella pneumoniae nosocomial strains isolated from Russia
Abstract number: P1199
Fursova N., Pryamchuk S., Abaev I., Shishkova N., Pecherskikh E., Kruglov A., Sidorenko S., Svetoch E., Weigel L., Rasheed J.
Objectives: Characterisation of the genetic environment flanking blaCTX-M gene subtypes [blaCTX-M-1 (n = 50, 64%), blaCTX-M-9 (n = 24, 30%), blaCTX-M-2 (n = 5, 6%)] that had been identified in Escherichia coli (n = 54) and Klebsiella pneumoniae (n = 25) strains isolated in Russia from 2003 to 2007.
Methods: PCR mapping, PCR-RFLP, and DNA sequencing were used for detection, localisation, and identification of blaCTX-M genes and their surrounding regions. Specific primers for detection of mobile genetic elements ISEcp1, IS26, IS903, ORF513, ORF477, and mucA were previously described (Eckert C. et al., 2006).
Results: Variability found in the genetic environment surrounding blaCTX-M genes included rearrangements of ISEcp1 mobile element upstream of blaCTX-M, short specific nucleotide sequences between ISEcp1 and blaCTX-M, and variations in the downstream flanking region. ISEcp1 mobile element (intact or partially truncated) was identified upstream of blaCTX-M in nearly all bacterial isolates under study. Another mobile element, ORF513, was found in only one strain (Fig. 1). Intact ISEcp1 was found in 39 strains; deletion of tnpA or other modifications in the 5' flanking region in 17 strains; insertions of other IS elements into ISEcp1 (IS26, IS10, IS1, or resolvase Tn3) in 19 strains. Short nucleotide sequence insertions between ISEcp1 and blaCTX-M were found to be, generally, subtype-specific: 127 bp for blaCTX-M-1 in K. pneumoniae; 48 bp for blaCTX-M-1 in E. coli; 42 bp for blaCTX-M-9; and 19 bp for blaCTX-M-2. Three E. coli strains, however, were exceptions in that they contained 127 bp (n = 2), and 45 bp (n = 1) insertions. IS903 (intact or partially truncated) in the downstream region flanking blaCTX-M-9 was found in all bacterial isolates containing this subtype. ORF477 and mucA sequences were detected downstream of blaCTX-M-1 genes in nine isolates (Fig. 1).
Conclusion: The genetic environment of blaCTX-M genes was found to differ among CTX-M subgroups and bacterial genera suggesting differences in the mechanism of gene transmission. The presence of various mobile elements, such as IS elements, in the regions surrounding blaCTX M genes is likely key in evolution mechanisms of antibiotic resistance.
Acknowledgements: This study was done within the framework of the ISTS#2913/BTEP#62 Project.
Figure 1. Genetic environments of blaCTX-M genes (blaCTX-M-1, -9, and -2 subgroups) location of rearrangements in different strains.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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