KlcA genes are ubiquitous in clinical, bla-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 bla gene, which encodes beta lactamase, essentially all the plasmids contained a putative anti-restriction protein-encoding gene, KlcA. The KlcA gene was found in 98.2% of the bla-positive, imipenem-resistant K. pneumoniae clinical isolates and in <1% of the bla-negative control group. A searched of the GenBank database indicated that KlcA 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 KlcA and other KlcAs. The secondary structure of KlcA, predicted with PROMALS3D software, exhibited highly conserved α-helices and β-strands. KlcA expressed anti-restriction activity in vivo. In summary, KlcA genes are ubiquitous in bla-positive Klebsiella pneumoniae clinical isolates collected at Huashan Hospital, China. The KlcA protein possesses a secondary structure similar to that exhibited by anti-restriction proteins and displays anti-restriction activity. As such, KlcA is a probable factor in the accelerated spread of bla and carbapenem-resistance among clinical, K. pneumoniae isolates.