Occurrence of healthcare-associated infections caused by the zoonotic bacterium Pasteurella multocida subsp. gallicida in patients with severe motor and intellectual disabilities in Japan.

Abstract

Purpose: Pasteurella multocida is an important zoonotic pathogen that can cause human infections, exhibiting a wide clinical spectrum ranging from localised bite-wound infections to invasive infections, particularly in immunocompromised patients. The detection of P. multocida isolates from three patients with severe motor and intellectual disabilities (SMID) led to an investigation into the genomic relationship to explore nosocomial transmission.

Methods: Three P. multocida strains were isolated from transtracheal aspirate cultures taken from three different inpatients in the SMID ward between January and February 2025. All strains were identified by phenotypic tests and MALDI-TOF MS. Whole-genome sequencing was performed to identify subspecies, analyze virulence genes, and explore phylogenetic relatedness.

Results: Three strains were identified as P. multocida subsp. gallicida, based on dDDH values of 89.6% and ANIm values of ≥98.89%. They belonged to novel sequence types multihost ST371 and RIRDC ST585, the capsular genotype of closest to type A, predominantly found in human respiratory pathogens, and the lipopolysaccharide genotypes of L1. They shared virulence genes encoding outer membrane proteins, adhesion factors, superoxide dismutases and hyaluronidases. The number of SNP differences between the three strains was found to be one or less, indicating that these strains are almost genetically indistinguishable.

Conclusions: A noteworthy aspect of the present study is that it is the first to report intra-hospital transmission of P. multocida subsp. gallicida, as demonstrated through genome-level analysis. It is crucial to recognise that healthcare-associated infection caused by P. multocida can occur in specialised medical settings, such as wards for patients with SMID.