Tracking Short-term changes in the genetic diversity and antimicrobial resistance of OXA-232-producing Klebsiella pneumoniae ST14 in clinical settings

Abstract Objectives To track stepwise changes in genetic diversity and antimicrobial resistance in rapidly evolving OXA-232-producing Klebsiella pneumoniae ST14, an emerging carbapenem-resistant high-risk clone, in clinical settings. Methods Twenty-six K. pneumoniae ST14 isolates were collected by the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) system over the course of 1 year. Isolates were subjected to whole-genome sequencing and minimal inhibitory concentration determinations using 33 antibiotics from 14 classes. Results Single-nucleotide polymorphism (SNP) typing identified 72 unique SNP sites spanning the chromosomes of the isolates, dividing them into three clusters (I, II, and III). The initial isolate possessed two plasmids with 18 antibiotic resistance genes, including bla OXA-232 , and exhibited resistance to 11 antibiotic classes. Four other plasmids containing 12 different resistance genes, including bla CTX-M-15 and strA/B , were introduced over time, providing additional resistance to aztreonam and streptomycin. Moreover, chromosomal integration of IS Ecp1 - bla CTX-M-15 mediated the inactivation of mgrB responsible for colistin resistance in four isolates from cluster III. To the best of our knowledge, this is the first description of K. pneumoniae ST14 resistant to both carbapenem and colistin in South Korea. Furthermore, although some acquired genes were lost over time, the retention of 12 resistance genes and inactivation of mgrB provided resistance to 13 classes of antibiotics. Conclusions We described stepwise changes in OXA-232-producing K. pneumoniae ST14 in vivo over time in terms of antimicrobial resistance. Our findings contribute to our understanding of the evolution of emerging high-risk K. pneumoniae clones and provide reference data for future outbreaks.