High-risk KPC-producing Klebsiella pneumoniae lack type I R-M systems

Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) have disseminated worldwide and are a major threat to public health. The multidrug-resistant (MDR)-phenotype of KPC-KP are commonly associated with the presence of high molecular weight bla(KPC) plasmids. Restriction-modification (R-M) systems provide bacteria with innate defense against plasmids or other infectious gene elements. As bla(KPC) plasmids are favored by such MDR K. pneumoniae, it was of interest to examine the co-distribution of R-M and acquired bla(KPC) plasmids in KPC-KP. A total of 459 clinical K. pneumoniae isolates in China and 217 global whole-genome sequences in GenBank were collected to determine the prevalence of type I R-M systems. The type I R-M systems were scarce in the KPC-positive group and high-risk Klebsiella pneumoniae clonal group 258 (CG258). The polymorphisms of type I R-M observed in K. pneumoniae revealed the ubiquity of their recognition sequences in DNA; therefore, the type I R-M systems could attack most invading DNA elements, such as bla(KPC) genes. Overall, this work indicated the type I R-M systems may impact the acquisition of bla(KPC) genes in K. pneumoniae. (C) 2020 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.