The global rise of multidrug-resistant Klebsiella pneumoniae—especially carbapenem-resistant strains—poses a major clinical challenge. Data on the molecular characteristics of MDR K. pneumoniae in central Türkiye were limited. The present study aimed to characterize antimicrobial resistance patterns and molecular features of MDR K. pneumoniae recovered from hospitalized patients in a tertiary care ICU in central Türkiye.
Between November 2024 and June 2025, a total of 1,560 clinical specimens from ICU patients were analyzed. From these samples, 33 non-duplicate MDR K. pneumoniae isolates obtained from 26 patients were included in the study. The selection was restricted to unique isolates to avoid duplication from the same patient.
Identification and antimicrobial susceptibility testing were performed using the VITEK®2 system. The source report states that all included isolates were characterized as multidrug-resistant based on their susceptibility profiles determined by VITEK®2. Specific susceptibility percentages reported in the source are summarized below in the Antimicrobial resistance profiles section.
The study investigated a predefined set of resistance, virulence, and efflux-associated genes by PCR. Targeted genes included extended-spectrum β-lactamase (ESBL) determinants: blaTEM, blaSHV, and blaCTX-M group(s); carbapenemase genes: blaKPC, blaOXA-48, and blaNDM-1; virulence-associated genes: iucA and rmpA2; and efflux pump genes acrAB and tolC. Clonal relatedness among isolates was assessed using pulsed-field gel electrophoresis (PFGE).
All isolates displayed resistance to multiple β-lactams as well as to ciprofloxacin. Reported resistance rates include:
These findings illustrate very high levels of resistance to carbapenems and aminoglycosides among the sampled ICU isolates, with lower but notable resistance to last-line agents such as colistin and to newer combinations such as ceftazidime–avibactam.
PCR screening identified a high prevalence of ESBL genes and a substantial presence of an OXA-48–type carbapenemase among isolates. Gene frequencies reported in the source are:
Regarding virulence markers, none of the isolates carried the tested hypervirulence-associated genes iucA or rmpA2. The source notes that occasional hypermucoviscosity was observed phenotypically, but molecular markers of hypervirulence were not found.
The source also indicates that efflux pump genes acrAB and tolC were investigated by PCR; presence of these genes was part of the molecular characterization, though the abstract does not report the exact detection frequencies for acrAB and tolC.
Pulsed-field gel electrophoresis revealed substantial genetic heterogeneity among the isolates. Multiple pulsotypes were identified, and no single epidemic clone dominated the ICU population during the study period. The PFGE results indicate dissemination of multiple genetically distinct MDR K. pneumoniae lineages rather than clonal expansion of one strain.
The study documents dissemination of genetically diverse MDR K. pneumoniae lineages in an ICU setting in central Türkiye, with frequent carriage of ESBL genes and a high prevalence of OXA-48 carbapenemase. High resistance rates to meropenem, amikacin, and gentamicin, together with measurable resistance to colistin and ceftazidime–avibactam in a subset of isolates, emphasize limited therapeutic options.
Although some isolates showed hypermucoviscosity phenotypically, the absence of iucA and rmpA2 indicates a lack of molecular evidence for classical hypervirulence in these strains. The combination of multidrug resistance and diverse clonal backgrounds supports the need for continuous molecular surveillance, robust infection-control practices, and antimicrobial stewardship in the ICU.
The source abstract provides key methods and results but does not report several potentially relevant details in the abstract text. For example, the abstract does not provide patient-level clinical outcomes, specific specimen types for each isolate, exact frequencies for efflux gene detection (acrAB, tolC), timing of phenotypic hypermucoviscosity observations, or detailed PFGE dendrogram data. These elements may be present in the full text but were not reported in the abstract used as the source.
In summary, the study's abstract documents a high burden of genetically diverse, multidrug-resistant Klebsiella pneumoniae carrying ESBLs and OXA-48 in a tertiary ICU in central Türkiye and calls for ongoing molecular monitoring and infection-control reinforcement.