Single-locus-sequence-based typing of blaOXA-51-like genes for rapid assignment of Acinetobacter baumannii clinical isolates to international clonal lineages

Abstract

Single-locus blaOXA-51-like sequence-based typing (SBT) was evaluated for its ability to determine correctly sequence types (STs) in Acinetobacter baumannii clinical isolates, in comparison with the Pasteur's multilocus sequence typing (MLST) reference method and 3-locus sequence typing (3-LST). The comparative study was performed in 585 multidrug-resistant (MDR) A. baumannii clinical isolates recovered from 21 hospitals located throughout Greece, Italy, Lebanon, and Turkey. The isolates belonged to nine clonal complexes (CCs) that correspond to 12 distinct sequence types (STs) and to one singleton ST. These clonal lineages predominate worldwide among nosocomial MDR A. baumannii strains. The most common clone was CC2 (ST2 and ST45; n=278 isolates) followed by CC1 (ST1 and ST20; n=155), CC25 (n=65), ST78 (n=62), CC15 (ST15 and ST84; n=9), CC10 (n=4), CC3 (n=4), CC6 (n=3), CC54 (n=3), and CC83 (n=2). Using the blaOXA-51-like SBT method, all 585 isolates of the study were typed and assigned correctly to the nine CCs and the singleton ST78. The 3-LST method was not able to classify isolates belonging to CC6, CC10, CC54, and CC83, which are not yet characterized in its database. The low-cost and convenient blaOXA-51-like SBT method, compared with 3-LST and MLST, discriminated all epidemic and sporadic lineages of our collection and could be effectively applied to type rapidly A. baumannii strains.

FIG 1

Neighbor-joining phylogenetic trees based on bla_OXA-51like genes (A) and concatenated alleles of the seven housekeeping genes of Pasteur's MLST scheme (B). The dendrograms show the amounts of genetic change based on multiple alignments and were generated using phylogeny.fr software (17). The bar at the bottom of each figure shows the amount of genetic change corresponding to the length of each branch.