Misidentification of Raoultella spp. (R. terrigena, R. planticola) and Klebsiella spp. (K. variicola, K. grimontii) as Klebsiella pneumoniae: Retrospective study of a necropsy-associated bacterial collection from horses.

This research paper focuses on studying the misidentification of bacterial strains – primarily Raoultella and Klebsiella species – as Klebsiella pneumoniae within a collection obtained from horse autopsies.

Objective of the Study

• The main objective is to better understand the 12 Raoultella and Klebsiella strains involved in this misidentification process during the study.

Methods used in the Research

• The strains were identified using several technical methods, including the Api 20E system, detection via K. pneumoniae PCR, matrix-assisted laser desorption/ionisation time-of-flight mass spectroscopy (MALDI-TOF), and whole-genome sequencing.

Testing of Antimicrobial Susceptibilities

• The research went further by testing the strains’ antimicrobial susceptibilities using the disc diffusion method, involving a panel of 40 antibiotics.

Key Findings

• The main misidentifications concern Raoultella species (specifically, R. terrigena and R. planticola) as K. pneumoniae, rather than Klebsiella species (specifically, K. variicola and K. grimontii), with R. terrigena being the dominant strain.
• Among the 12 strains, it was found that only K. grimontii was multi-drug resistant, and none of the other strains were identified as hypervirulent.
• MALDI-TOF was found to be a reliable method to avoid such misidentification, however, the researchers suggest expanding commercial spectrum databases with K. grimontii and R. terrigena reference spectra to enhance the accuracy of the identification process.
• The research provides the first report of K. grimontii and R. planticola isolations from horses, as well as the second report of R. terrigena and K. variicola isolations from horses.