Comparison of the Pathogenic Potential of Campylobacter jejuni, C. upsaliensis and C. helveticus and Limitations of Using Larvae of Galleria mellonella as an Infection Model

Abstract

Campylobacter enteritis in humans is primarily associated with C. jejuni/coli infection. Other species cause campylobacteriosis relatively infrequently; while this could be attributed to bias in diagnostic methods, the pathogenicity of non-jejuni/coli Campylobacter spp. such as C. upsaliensis and C. helveticus (isolated from dogs and cats) is uncertain. Galleria mellonella larvae are suitable models of the mammalian innate immune system and have been applied to C. jejuni studies. This study compared the pathogenicity of C. jejuni, C. upsaliensis, and C. helveticus isolates. Larvae inoculated with either C. upsaliensis or C. helveticus showed significantly higher survival than those inoculated with C. jejuni. All three Campylobacter species induced indistinguishable histopathological changes in the larvae. C. jejuni could be isolated from inoculated larvae up to eight days post-inoculation whereas C. upsaliensis and C. helveticus could only be isolated in the first two days. There was a significant variation in the hazard rate between batches of larvae, in Campylobacter strains, and in biological replicates as random effects, and in species and bacterial dose as fixed effects. The Galleria model is applicable to other Campylobacter spp. as well as C. jejuni, but may be subject to significant variation with all Campylobacter species. While C. upsaliensis and C. helveticus cannot be considered non-pathogenic, they are significantly less pathogenic than C. jejuni.

Virulence assessment of enterohepaticHelicobacterspecies carried by dogs using the wax moth larvaeGalleria mellonellaas infection model

“…Similar results were reported evaluating pathogenicity of C. jejuni, C. upsaliensis, and C. helveticus. 18 The latter were successfully recovered in the first 2 days suggesting these species were less pathogenic than C. jejuni, which was isolated up to 8 days pi. In contrast, EHH species evaluated in this study appear to be less pathogenic due to the fact that their recovery from the hemolymph of the larvae was achieved only on the first day pi.…”

“…Similar results were reported for C. jejuni, C. upsaliensis, and C. helveticus where melanization was also observed. 16,18 EHH species induced different degrees of histopathological changes in the larvae. Histopathology findings displayed cellular and humoral immune response which correlate well with the results reported for other taxonomically related bacteria.…”

“…Histopathology findings displayed cellular and humoral immune response which correlate well with the results reported for other taxonomically related bacteria. 16,18 The cellular immune response showed different dynamics between infection with the different EHH isolates. The difference in the cellular immune response of G. mellonella led us to infer that the presence of different virulence factors can induce different immune responses.…”

“…mellonella has been used to assess the virulence of Campylobacter jejuni 15,16 and Helicobacter pylori , 17 allowing the screening of their virulence determinants. Furthermore, the pathogenicity of other emerging campylobacters such as Campylobacter upsaliensis and Campylobacter helveticus was recently demonstrated using this larvae model 18 . However, despite the increasing importance of EHH species as emerging animal and human's pathogens, no investigations have tested the efficacy of this model for studying their pathogenicity yet.…”

“…Furthermore, the pathogenicity of other emerging campylobacters such as Campylobacter upsaliensis and Campylobacter helveticus was recently demonstrated using this larvae model. 18 However, despite the increasing importance of EHH species as emerging animal and human's pathogens, no investigations have tested the efficacy of this model for studying their pathogenicity yet. Therefore, we aimed to determine the pathogenic potential of EHH species isolated from dogs in G. mellonella larvae as an infection model.…”