Transcellular penetration of <i>Treponema phagedenis</i> isolated from papillomatous digital dermatitis in polarized normal human epidermal keratinocytes <i>in vitro</i>

Abstract

Papillomatous digital dermatitis (PDD) is a polymicrobial infection causing lameness in dairy cattle. Culture-independent analysis has shown that Treponema phagedenis is present consistently and predominantly in the lesions. However, the pathogenesis of PDD, especially the tissue penetration pathway, has not been examined. In the present study, we investigated whether T. phagedenis strains isolated from PDD produce proteolytic enzyme(s) for disruption of the epithelial cell barrier and have the ability to translocate in polarized normal human epidermal keratinocytes (NHEK) in vitro. Ten strains of T. phagedenis isolated from lesions did not show proteolytic activity on modified skim milk agar, although a human strain of T. denticola used as a control showed such activity. The integrity of tight junctions was monitored by measurement of transepithelial electrical resistance (TER). The TER values after inoculation of the T. phagedenis strains examined did not change during the experimental period; however, apical to basolateral translocation of T. phagedenis was confirmed after 24 hr by microscopy and Treponema-specific PCR. We further confirmed that translocation of T. phagedenis was accelerated by co-inoculation with live T. denticola, but not with heat-killed organisms. Furthermore, tight junction ZO-1 protein was not lost intensity after inoculation with T. phagedenis and the organism was observed in NHEK cells using a florescence microscope. These results suggest that T. phagedenis strains may translocate via a transcellular route in vitro and that the invasion is accelerated by other bacteria, such as T. denticola, producing proteolytic activity.

Case Report: Detection of Treponema phagedenis in cerebrospinal fluid of a neurosyphilis patient by metagenomic next-generation sequencing

“…Their results also indicated that the sequence of T. phagedenis genomes originating from bovine and humans were highly conserved; only slight variations can distinguish isolates from different host sources. As an accepted key agent in the pathogenesis of bovine digital dermatitis, a widespread infectious foot condition of economic and animal welfare importance, T. phagedenis has been reported many times over the years ( Rosander et al., 2011 ; Espiritu et al., 2020 ; Khemgaew et al., 2021 ). T. phagedenis has never been detected from the central nervous system (CNS) (using any method).…”

Diagnosis, treatment, and control of bovine digital dermatitis in dairy cattle

“…While Read and Walker (1998a) concluded pre-existing trauma not essential for lesion induction, the final lesion induction protocol of Krull et al (2016a) included skin abrasion as a pre-condition. Apart from the cattle model, other strategies used to elucidate the etiology of digital dermatitis are a sheep and murine abscess model (Elliott et al, 2007;Wilson-Welder et al, 2018b;Arrazuria et al, 2020), and studies using digital dermatitis lesion biopsies, human epidermal keratinocytes, bovine foot skin fibroblasts, genomics, proteomics, or a combination of these techniques and animal models (Wilson-Welder et al, 2018a;Nally et al, 2019;Bonacin et al, 2020;Espiritu et al, 2020;Khemgaew et al, 2021;Newbrook et al, 2021;Staton et al, 2021). In general, these studies investigated the host-pathogen interactions related to digital dermatitis at histopathological, immunological, or genetic level.…”