Background/Objectives: Klebsiella pneumoniae ST307 is emerging as a significant global high-risk antimicrobial-resistant (AMR) clone with a notable capacity to acquire and disseminate resistance genes. However, there is limited research on the pathogenicity, virulence, and adaptation of ST307 strains and on the clinical characteristics of infected patients. Methods: In this study, a carbapenem-resistant K. pneumoniae (CRKP) ST307 strain named U989 was isolated from a urine culture of a hospitalized patient in Volos, Greece, in July 2024. Whole-genome sequencing was performed to identify resistance genes to β-lactams bla_KPC-2, bla_CTX-M-15, bla_TEM-1B, bla_OXA-1, bla_OXA-10, bla_SHV-106, and bla_VEB-1 and resistance genes to other antibiotics. Results: A genomic analysis also revealed the presence of virulence factors such as iutA, clpK1, fyuA, fimH, mrkA, Irp2, and TraT and an IncFiB(pQil)/IncFII(K) replicon, which harbors the bla_KPC-2 gene. Additionally, the transposable element Tn4401 was identified as a key vehicle for the mobilization of the bla_KPC-2 resistance gene. Finally, this is the report of a high-risk CRKP ST307 clone expressing KPC-2, SHV-106, CTX-M-15, and VEB-1 bla genes in Greece. Conclusions: The coexistence of these resistance genes in addition to aminoglycoside, quinolone, and other resistance genes results in difficult-to-treat infections caused by respective carrier strains, often requiring the use of last-resort antibiotics and contributing to the global challenge of antimicrobial resistance.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a growing threat in Greek hospitals, with increasing reports of multidrug- and pandrug-resistant strains; however, molecular data from regional centers remain limited. This study aimed to investigate the molecular epidemiology, resistance mechanisms, and transmission dynamics of CRKP isolates collected at the General Hospital of Volos, Central Greece, between 2022 and 2024. Thirty-seven non-duplicate CRKP isolates were analyzed. Identification and antibiotic susceptibility testing were performed using VITEK® 2, disk diffusion, Etest®, and broth microdilution. Carbapenemase production was assessed using the NG-Test® Carba-5. Eight isolates underwent multilocus sequence typing (MLST). All isolates were resistant to carbapenems, cephalosporins, and fluoroquinolones; furthermore, 40% were colistin-resistant. The dominant carbapenemase genes were bla_NDM-1 (45.9%), bla_KPC-2 (18.9%), and bla_VIM-1 (27.0%), with co-expression of multiple carbapenemases in 30% of the isolates. MLST revealed the high-risk clones ST11, ST15, and ST323, and three intra-intensive care unit (ICU) transmission clusters. The emergence of dual-carbapenemase and colistin-resistant clones underscores the need for local genomic surveillance, improved infection control, and access to newer antimicrobials in non-tertiary settings.

The spread of NDM-1-harboring Klebsiella pneumoniae is a worldwide concern. In this study the whole-genome sequence (WGS) of a carbapenem- and colistin-resistant K. pneumoniae 838Gr strain is presented. This strain was isolated from a urine sample of a patient in the Intensive Care Unit (ICU) at Volos Hospital, Greece. The initial assembly produced 224 contigs with a combined genome size of 5,561,803 bp and a GC content of 57.21%. The K. pneumoniae strain carried IncR, IncFIA, IncC, and repB (R1701) replicons. Multilocus sequence typing (MLST) analysis revealed that the isolate belonged to the sequence type 11 (ST11) and serogroup KL24 and O2a. The WGS analysis identified several beta-lactamase genes (bla_TEM-1B, bla_CTX-M-15, bla_NDM-1, bla_OXA-1, bla_VEB-1, bla_OXA-10, and bla_SHV-11) alongside resistance genes for other antibiotic classes, including floR2, cmlA1, cmlA5, catB3, arr-3, aph(6)-Id, aadA2. Colistin resistance was attributed to specific point mutations in pmrB (R256G, T140P). This is the first report of a carbapenem- and colistin-resistant K. pneumoniae ST11 strain in Greece. The findings of this study highlight the urgent need for increased surveillance and stringent infection control.

Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) threatens Intensive Care Units (ICU), particularly in settings where serine (KPC) and metallo-β-lactamases (NDM) co-circulate. The aim of this study was to assess CRKP susceptibility especially to novel β-lactam/β-lactamase inhibitor combinations, characterize the genetic determinants of resistance, and contribute to the understanding of local epidemiology in the ICU of our hospital. Methods: We studied 32 non-duplicate CRKP isolates (30 ICU, 2 wards) collected at Hippokration General Hospital, Thessaloniki (May–Oct 2023). Bacterial identification and Antimicrobial susceptibility testing (AST) were performed by VITEK-2; Minimum inhibitory concentrations (MICs) for ceftazidime/avibactam (CAZ/AVI), meropenem/vaborbactam (MER/VAB), and imipenem/relebactam (IMI/REL) were determined by E-tests. Colistin MICs were performed by broth microdilution. Carbapenemases were screened phenotypically and by immunochromatography and confirmed by multiplex PCR. One bronchial isolate co-harboring bla_NDM and bla_KPC genes underwent WGS. Results: All isolates were carbapenem-resistant and showed extensive resistance to β-lactams and fluoroquinolones. By PCR, 8/32 (25%) carried bla_KPC alone, 8/32 (25.0%) bla_NDM alone, and 16/32 (50%) co-harbored bla_KPC and bla_NDM. KPC-only isolates were generally susceptible in vitro to CAZ/AVI, MER/VAB, and IMI/REL, whereas dual KPC-NDM producers were resistant to all three combinations. Tigecycline showed the highest retained activity; colistin remained active in a minority. WGS of one ST512 (CG258) isolate revealed co-harboring bla_NDM-1 and bla_KPC-3 with additional resistance determinants and plasmid replicons, consistent with high-risk spread. Conclusions: Half of CRKP isolates in this ICU-predominant series co-produced KPC and NDM, severely limiting β-lactam/β-lactamase inhibitor options. These data support routine screening for carbapenemases, strict infection prevention, antimicrobial stewardship, and access to agents active against MBLs.

The emergence of carbapenemase-producing Klebsiella pneumoniae poses a significant global health threat, particularly in hospital settings. This study reports on the first detection of a pandrug-resistant (PDR) high-risk ST15 K. pneumoniae strain co-producing NDM-1 and VIM-1 in Greece. The isolate was recovered from a blood culture of a male patient admitted to the Intensive Care Unit (ICU) of Volos Hospital in July 2024. Next generation Sequencing (NGS) confirmed the presence of bla_NDM-1 and bla_VIM-1 genes. Other beta-lactamase type (CTX-M-15) was detected in association with NDM and VIM enzymes. Furthermore, this isolate was resistant to other antimicrobial agents, including aminoglycosides [aac(3)-II, aac(3)-IIe, aac(6′)-Ib, aadA1, aph(3″)-Ib, aph(6)-Id, aph(3′)-Ia), chloramphenicol (catB3), fluoroquinolones (qnrS1) and sulfonamides (sul1 and sul2). The Multilocus Sequence Typing revealed that the strain belonged to ST15. According to Kaptive the strain belonged to KL48. Our study provides new data about MBL producing K. pneumoniae in Greece. Thus, we report for the first time the co-expression of bla_NDM-1 and bla_VIM-1 in our country in ST15 K. pneumoniae. This study provides crucial epidemiological data on MBL-producing K. pneumoniae in Greece and highlights the urgent need for enhanced surveillance, infection control strategies, and access to last-resort antibiotics such as aztreonam-avibactam.

Klebsiella pneumoniae is a major human pathogen, because it causes both community- and hospital-acquired infections. Several multidrug-resistant high-risk clones of K. pneumoniae have been reported worldwide, and these are responsible for high numbers of difficult-to-treat infections. In Greece, a K. pneumoniae ST39 high-risk clone was detected in 2019 in a survey of carbapenem- and/or colistin-resistant Enterobacteriacae. The present study included nine carbapenem-resistant K. pneumoniae (CRKP) isolates collected during a retrospective analysis from October 2020 to December 2020. They were isolated from nine different patients hospitalized in the intensive care unit (ICU) of a hospital in Volos, Greece, and they were selected for analysis due to their phenotypic profile. In this study, we analyzed A165 strain K. pneumoniae ST39 isolated from a blood culture in November 2020. Whole-genome sequencing (WGS) was performed using Ion Torrent Platform, and resistance genes, virulence determinants, capsular types, insertion sequences, phage regions, and clustered regularly interspaced palindromic repeats (CRISPR) regions were detected by bioinformatic analysis. The molecular characterization revealed antimicrobial resistance genes, including sul2 for sulfamethoxazole; dfrA1 for trimethoprim; bla_VIM-1 and bla_KPC-2 for carbapenems; aac(6′)-II for aminoglycosides; fosA for fosfomycin and aad1 for streptomycin, bla_SHV-40, bla_SHV-85, bla_SHV-79, bla_SHV-56, and bla_SHV-89 for beta-lactams. Point mutations were identified in ompK36, and ompK37 and in acrR, gyrA, parC. Several replicons were found, including CoIRNA, IncC, IncFIB(K), IncFIB(pQiL), and IncFII(K). The capsular typing revealed that the strain was KL23, O2afg. The genome sequence of A165 was submitted to NCBI under PRJNA1074377 and have been assigned to Genbank accession number JAZIBV000000000.