Successful treatment of an intra-abdominal abscess caused by KPC-2-producing hypervirulent Klebsiella pneumoniae sequence type 11 with imipenem/cilastatin/relebactam in a Japanese patient

KPC-producing K. pneumoniae is rare in Japan. In China, KPC-2-producing sequence type (ST)11 K. pneumoniae isolates have been rapidly increasing, and a subset of these isolates have acquired hypervirulence. We report a case of a 39-year-old Japanese male who developed bacteremia and intra-abdominal abscesses caused by hypervirulent carbapenem-resistant K. pneumoniae. The patient sustained abdominal injuries following a traffic accident in Xinjiang Uygur Autonomous Region and underwent abdominal surgery before being transferred to our hospital. Abscess drainage was performed, and he was initially treated with meropenem (2 g every 8 hours, prolonged infusion over 3 hours), gentamicin (5 mg/kg/day), and tigecycline (200 mg as a loading, followed by 100 mg every 12 hours). KPC carbapenemase was detected using the NG-Test® CARBA 5 (NG Biotech, France), and the minimum inhibitory concentration for imipenem/cilastatin/relebactam was 1 μg/mL, indicating susceptibility. His treatment was switched to imipenem/cilastatin/relebactam (1 g every 6 hours) for 7 weeks, resulting in clinical improvement. Whole-genome sequencing analysis revealed that the causative strain was hypervirulent KPC-2-producing K. pneumoniae (capsular type K64, ST 11) carrying bla_KPC-2 and bla_CTX-M-65 on a multireplicon plasmid (pMTY24772_IncFII-R), which was a fusion of IncFII and IncR. Additionally, rmpA and iucABCD genes associated with hypervirulence were detected. The strain carried a resistance plasmid and a virulence plasmid similar to those carried by ST11-K64 KPC-producing strains reported from China. Imipenem/cilastatin/relebactam is potentially an option for treating infections caused by KPC-2-producing hypervirulent K, pneumoniae with porin mutations. Cross-border spread of pathogens that are both multidrug-resistant and hyperviirulent must be closely monitored.