Characterization of plasmids encoding blaESBL and surrounding genes in Spanish clinical isolates of Escherichia coli and Klebsiella pneumoniae.

OBJECTIVES: The aim of the study was to characterize plasmids that harbour blaESBL genes and their genetic environment in Escherichia coli and Klebsiella pneumoniae clones circulating in Spain.
METHODS: The incompatibility group of plasmids within 58 strains harbouring blaCTX-M (n=45) and blaSHV (n=15) genes was determined by rep-typing-PCR and hybridization. The blaESBL genetic environment was determined by PCR and sequencing.
RESULTS: The blaCTX-M-9 genes (n=14) were linked to In60 located in IncI1 (50%) or IncHI2 plasmids (28%). All blaCTX-M-14 genes (n=13) were flanked by ISEcp1 and IS903 and 12 were associated with IncK plasmids. One of two blaCTX-M-10 genes was present in an IncK plasmid, but both genes were linked to a phage-related element. Five of seven blaCTX-M-1 (71%), all three blaCTX-M-32 and one of two blaCTX-M-3 genes were linked to IncN plasmids. The other blaCTX-M-3 gene was linked to IncA/C and the remaining two blaCTX-M-1 genes to IncFII plasmids. Three blaCTX-M-15 genes were associated with IncF (repFIA) and one with IncFII plasmids. All these genes from blaCTX-M group-1 showed the ISEcp1 upstream truncated by different insertion sequences. Forty-three percent of blaSHV-12 genes (n=14) were located in IncI1 plasmids, all flanked by the IS26 and DEOR region. The only detected blaSHV-5 gene was located in an IncFII plasmid and flanked by recF and DEOR regions.
CONCLUSIONS: A diversity of the plasmid incompatibility groups that harbour blaESBL genes was observed, except for the blaCTX-M-14 gene. Moreover, a high variability was confirmed in the genetic environment of these genes as a result of insertion and deletion events.