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

Abstract

ABSTRACT 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 bla OXY gene (i.e., bla OXY-1 or bla OXY-2 ). K. oxytoca strains SG266 and SG271 could not be classified into these genetic groups based on their ERIC-1R profile and bla OXY gene sequence. With regard to the gene identity percentages between the bla OXY-1 and bla OXY-2 gene groups (86.8% ± 0.4%) and within a bla OXY gene group (>99%), it was concluded that the bla OXY gene of strain SG271 was representative of a new bla OXY gene group ( bla OXY-3 ), since the mean identity percentages between it and the two bla OXY 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 bla OXY gene, which was therefore named bla OXY-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.