Variants of the Klebsiella pneumoniae OKP Chromosomal Beta-Lactamase Are Divided into Two Main Groups, OKP-A and OKP-B

Abstract

Two bla OKP subgroups were found, diverging by 4.2%. Subgroups bla OKP-A (10 enzyme variants, pIs from 7.1 to 8.3) and bla OKP-B (11 variants, pI 7.1) showed similar antibiotic susceptibilities. Sequencing of rpoB, gyrA, and mdh demonstrated a concordant subdivision of Klebsiella pneumoniae phylogenetic group KpII into two subgroups, KpII-A and KpII-B.Klebsiella pneumoniae clinical isolates are naturally resistant to ampicillin, amoxicillin, carbenicillin, and ticarcillin, but not to extended-spectrum beta-lactams, due to the constitutive expression of a chromosomally encoded beta-lactamase. Three families of the chromosomal beta-lactamase gene, bla SHV , bla OKP , and bla LEN, evolved from a common ancestor over millions of years, in parallel with the diversification of the three K. pneumoniae phylogenetic groups KpI, KpII, and KpIII (3, 6). The bla OKP family was found in group KpII (6) and was more heterogeneous than the SHV and LEN families, with four OKP enzyme variants. These variants appeared to belong to two OKP subgroups, but a higher number of variants was judged necessary to firmly demonstrate the phylogenetic distinctness of these subgroups (6). In addition, because homologous recombination is more frequent among closely related strains than between distant phylogenetic groups (8, 10), the correspondence observed at the level of the three phylogenetic groups between beta-lactamase and housekeeping gene classifications (5, 6) could be disrupted by homologous gene transfer within KpII.Precise identification of bla variants can be critical for epidemiological purposes and infection control. The objectives of the present study were to discover additional OKP enzyme variants, to determine whether strains harboring distinct OKP variants differ in their antibiotic susceptibility, and to determine whether bla OKP gene variants are subdivided into groups that correspond to housekeeping gene sequence groups.In order to discover new OKP variants,

Molecular identification of blaSHV, blaLEN and blaOKP β-lactamase genes in Klebsiella pneumoniae by bi-directional sequencing of universal SP6- and T7-sequence-tagged blaSHV-PCR amplicons

“…The necessity of obtaining complete sequences of bla SHV, bla LEN and bla OKP genes with appropriate primer-pairs was pointed out [10,11,19]. Moreover, the phylogenetic tree that was established is in agreement with a previous report describing three major groups of sequences corresponding to the bla SHV , bla LEN and bla OKP families of β-lactamase genes [9,12,13].…”

“…It was proposed that the chromosomally encoded bla LEN and bla OKP enzymes should be grouped in a single new family "K. pneumoniae-specific chromosomal β-lactamases," excluding plasmid encoded bla SHV enzymes from this family [11]. Furthermore, it has been shown that variants of chromosomally encoded K. pneumoniae OKP β-lactamases comprise two main groups, the bla OKP-A and bla OKP-B β-lactamases [12,13].…”

wzi Gene Sequencing, a Rapid Method for Determination of Capsular Type for Klebsiella Strains

“…Based on the phylogenetic analysis of the rpoB gene sequence (see Fig. S1 in the supplemental material), the 77 reference strains were attributed to K. pneumoniae (n ϭ 54), including three strains (K50, K60, and K80) corresponding to phylogenetic group KpII-B (40) wzi sequencing of K-type reference strains. wzi is one of the few genes present in the capsular polysaccharide cluster of all capsular types of K. pneumoniae.…”

Genomic analysis of diversity, population structure, virulence, and antimicrobial resistance in Klebsiella pneumoniae , an urgent threat to public health

“…Although it is clear that K. pneumoniae is genetically and phenotypically diverse (12,13), previous efforts to identify specific features that can distinguish human clinical isolates from plant, animal, or environmental isolates have yielded no markers of humanspecific lineages (14). Three distinct phylogroups of K. pneumoniaeKpI, KpII, and KpIII-have been defined based on sequencing of a small number of genes (15,16), and it has been proposed that these phylogroups be redesignated as distinct species, namely, K. pneumoniae (KpI), K. quasipneumoniae (KpII) (17), and K. variicola (KpIII) (18); however, all three cause infections in humans (15,19).…”