Providencia heimbachae Associated with Post-weaning Diarrhea in Piglets: Identification, Phenotype, and Pathogenesis

Despites Providencia heimbachae has been isolated from human, penguin, and bovine fetus, relatively little information is available regarding the pathogenicity and biologic characteristics of P. heimbachae. Here, we report that investigation of post-weaning diarrhea yielded bacterial isolates identified as P. heimbachae based on the biochemical tests and 16S ribosomal DNA sequence analysis. The two isolates were positive for utilization of Malonate, no gas production from glucose, and non-fermentation of D-mannitol, D-Galactose, and L-Rhamnose that were different from those of the type strain, and both of them have the ability of adhesion and invasion to IPEC-J2 cells, and were resistant to 21 out of the 41 antibiotics tested. In addition, the isolate 99101 was highly pathogenic to mice and piglets. Histopathology studies on nerve tissue of piglets that developed hindlimb paralysis showed microglia cell infiltration and neuron damage in the spinal cord. Notably, the strains could grow under low temperature (4 °C), which raise attention of a new risk factor for food safety. To the best of our knowledge, this is the first report of P. heimbachae strain caused post-weaning diarrhea in piglets in both natural and experimental conditions. These findings extended the knowledge of P. heimbachae as an important zoonotic agent, which should be given more attention during surveillance and diagnostics.