New Klebsiella oxytoca β-Lactamase Genes blaOXY-3 and blaOXY-4 and a Third Genetic Group of K. oxytoca Based on blaOXY-3

摘要

The two genetic groups (oxy-1 and oxy-2) previously identified in the Klebsiella oxytoca taxon are recognizable by four independent molecular markers: (i) ERIC-1R profiles, (ii) 16S ribosomal DNA (rDNA) signature sequences, (iii) singular nucleotides in a defined fragment of the rpoB gene, and (iv) the type of the strain's blaOXY gene (i.e., blaOXY-1 or blaOXY-2). K. oxytoca strains SG266 and SG271 could not be classified into these genetic groups based on their ERIC-1R profile and blaOXY gene sequence. With regard to the gene identity percentages between the blaOXY-1 and blaOXY-2 gene groups (86.8% ± 0.4%) and within a blaOXY gene group (>99%), it was concluded that the blaOXY gene of strain SG271 was representative of a new blaOXY gene group (blaOXY-3), since the mean identity percentages between it and the two blaOXY gene groups were 85.5% ± 0.2% and 84.4% ± 0.4%, respectively. Since the corresponding percentages were 95.0% ± 0.4% and 86.2% ± 0.3% for strain SG266, it was impossible to classify its blaOXY gene, which was therefore named blaOXY-4. The 16S rDNA signature sequences of the two strains could be determined only after cloning experiments. The SG266 clones displayed the same signature sequence as that of the genetic group oxy-1, whereas the SG271 clones displayed three different 16S rDNA signature sequences that also differed from those of the two genetic groups. Singular nucleotides were found within the rpoB sequence of the two strains, allowing for their distinction from the two genetic groups. All of these results, combined with those previously obtained by the ERIC-1R PCR method, indicate that strain SG271 is representative of a new K. oxytoca genetic group (oxy-3), whereas strain SG266 could not be classified.