KlcAHS genes are ubiquitous in clinical, blaKPC-2-positive, Klebsiella pneumoniae isolates.

Carbapenemase-producing Klebsiella pneumoniae has emerged and spread widely throughout the world. The mechanisms involved remain unclear. To provide insight, five plasmids were obtained from carbapenemase-producing K. pneumoniae clinical isolates. The five sequences were acquired, aligned and analyzed. In addition to the blaKPC-2 gene, which encodes beta lactamase, essentially all the plasmids contained a putative anti-restriction protein-encoding gene, KlcAHS. The KlcAHS gene was found in 98.2% of the blaKPC-2-positive, imipenem-resistant K. pneumoniae clinical isolates and in <1% of the blaKPC-2-negative control group. A searched of the GenBank database indicated that KlcAHS was mainly submitted by Chinese investigators beginning in 2010. Seventeen different KlcA amino acid sequences were found in the database using the restricting words: KlcA and Klebsiella pneumoniae. These sequences were used to generate a phylogenetic tree via MEGA6 software, revealing a distant evolutionary relationship between KlcAHS and other KlcAs. The secondary structure of KlcAHS, predicted with PROMALS3D software, exhibited highly conserved α-helices and ß-strands. KlcAHS expressed anti-restriction activity in vivo. In summary, KlcAHS genes are ubiquitous in blaKPC-2-positive Klebsiella pneumoniae clinical isolates collected at Huashan Hospital, China. The KlcAHS protein possesses a secondary structure similar to that exhibited by anti-restriction proteins and displays anti-restriction activity. As such, KlcAHS is a probable factor in the accelerated spread of blaKPC-2 and carbapenem-resistance among clinical, K. pneumoniae isolates.