Comparison of three routine methods for the identification of Kerstersia gyiorum from routine diagnostics and review of the literature

Why clinicians should know about it

• Picked for Microbiology (medical) (paper of the day, 23 October 2026): Compares routine identification methods for an emerging human pathogen

Abstract

INTRODUCTION: Since its first description in 2003, clinical case reports have repeatedly documented that the bacterial species Kerstersia gyiorum is a human pathogen. K. gyiorum has been described in the context of wound and middle ear infections, has been found in urine samples, and has even been recognized as a causative agent of septicemia. However, the pathogenic potential of K. gyiorum cannot be clearly determined due to the current lack of information about this species. To reveal the clinical significance of K. gyiorum, it is therefore essential to first create a clearly defined reference collection of isolates obtained from routine clinical diagnostics. METHODS: The aim of this study is to determine the most appropriate method for identifying K. gyiorum in routine diagnostics. To this end, three widely used routine methods (VITEK 2, MALDI-TOF MS, and 16S rRNA gene sequencing) were employed, and the accuracy of their results for K. gyiorum identification was compared. To ensure accurate species identification, dDDH (an NGS-based identification strategy) was used as the reference method. Furthermore, this manuscript provides an overview of all cases reported in the literature to date and discusses the accuracy of the identification results reported in these studies. In addition, genomic studies (pangenome and ANI matrix) were conducted using in silico analyses to investigate the clonal relationships among the isolates. RESULTS: The results show that MALDI-TOF MS is best suited for identifying K. gyiorum in routine diagnostics. However, in contrast to most publications, 16S rRNA gene sequencing was not suitable, as it was impossible to distinguish K. gyiorum from other members of the Alcaligenaceae family. The VITEK 2 system must also be considered unreliable for the correct identification of K. gyiorum. Additionally, this study identified a candidate for an undescribed species of the genus Kerstersia. DISCUSSION: MALDI-TOF MS is well suited for expanding the reference collection directly from routine diagnostics. The results of 16S gene sequencing should be interpreted with caution. Conversely, biochemical methods must be regarded as unreliable. The species' large core genome suggests a specialized previously unknown specialized ecological niche. Furthermore, two distinct clusters within the reference collection suggest a common origin. Additionally, follow-up studies must determine whether one isolate that cannot be unambiguously assigned to a species represents a previously undescribed member of the genus Kerstersia.

Abstract as published, via PubMed.