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Detection and characterization of putative hypervirulent Klebsiella pneumoniae isolates in microbiological
Bernd Neumann1,2, Claudia Stürhof3, Anca Rath4
1Institute of Clinical Microbiology, Infectious Diseases and Infection Control, Paracelsus Medical University, Nuremberg General Hospital, Nuremberg, Germany. bernd.neumann@klinikum-nuernberg.de.
Abstract:
Hypervirulent Klebsiella pneumoniae strains (hvKp) can cause invasive community-acquired infections in healthy patients of all ages. In this study, the prevalence of putative hvKp in a German tertiary center was investigated and hvKp were characterized by phenotypic and molecular assays. All K. pneumoniae isolates in routine microbiological diagnostics from a single center were screened by string-testing over a period of 6 months. String-test positive (≥ 0.5 mm) isolates were re-evaluated on different media and under various conditions (aerobe, anaerobe). For string-test positive isolates, genes (magA, iutA, rmpA and rmpA2) associated with hypermucoviscosity and hypervirulence were amplified by multiplex PCR. PCR-positive isolates were subjected to whole-genome sequencing and sedimentation and biofilm formation assays. From 1310 screened K. pneumoniae isolates in clinical routine 100 isolates (7.6%) were string test positive. From these, 9% (n = 9) were defined as putative hvKp (string-test+/PCR+). Highest rate of string-test-positive isolates was observed on MacConkey agar under aerobic conditions. Amongst these nine putative hvKp isolates, the international lineage ST23 carrying hvKp-plasmid pKpVP-1 was the most common, but also a rare ST86 with pKpVP-2 was identified. All nine isolates showed hypermucoviscosity and weak biofilm formation. In conclusion, 9% of string-positive, respectively 0.69% of all K. pneumoniae isolates from routine were defined as putative hypervirulent. MacConkey agar was the best medium for hvKp screening.
Insights
Hypervirulent Klebsiella pneumoniae (hvKp) strains are a growing concern. This study identified putative hvKp in 0.69% of clinical isolates, with MacConkey agar proving effective for screening.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Hypervirulent Klebsiella pneumoniae (hvKp) strains cause severe invasive infections.
- hvKp infections affect healthy individuals across all age groups.
- Understanding hvKp prevalence is crucial for public health.
Purpose of the Study:
- To determine the prevalence of putative hvKp in a German tertiary care setting.
- To characterize identified hvKp strains using phenotypic and molecular methods.
- To evaluate screening methods for hvKp detection.
Main Methods:
- Screening of 1310 K. pneumoniae isolates using the string test over six months.
- Phenotypic re-evaluation of string-test positive isolates under various conditions.
- Molecular identification of hypervirulence-associated genes (magA, iutA, rmpA, rmpA2) via multiplex PCR.
- Whole-genome sequencing and functional assays (sedimentation, biofilm formation) for PCR-positive isolates.
Main Results:
- 100 isolates (7.6%) were string-test positive.
- Nine isolates (0.69% of total, 9% of string-test positive) were classified as putative hvKp (string-test+/PCR+).
- MacConkey agar under aerobic conditions showed the highest rate of string-test positive isolates.
- International lineage ST23 with plasmid pKpVP-1 was most common; a rare ST86 with pKpVP-2 was also found.
- All nine hvKp isolates exhibited hypermucoviscosity and weak biofilm formation.
Conclusions:
- Putative hvKp strains represent a small but significant fraction (0.69%) of K. pneumoniae isolates in clinical routine.
- MacConkey agar is an effective medium for initial hvKp screening.
- Further characterization confirmed the hypervirulent phenotype and identified common and rare genetic lineages.
