Evaluation of Galleria mellonella larvae for studying the virulence of Streptococcus suis

Abstract

Background Streptococcus suis is an encapsulated Gram-positive bacterium and the leading cause of sepsis and meningitis in young pigs, resulting in considerable economic losses in the porcine industry. S. suis is considered an emerging zoonotic agent with increasing numbers of human cases over the last years. In the environment, both avirulent and virulent strains occur in pigs, with no evidence for consistent adapatation of virulent strains to the human host. Currently, there is an urgent need for a convenient, reliable and standardised animal model to rapidly assess S. suis virulence. Wax moth (Galleria mellonella) larvae have successfully been used in human and animal infectious disease studies. Here, we developed G. mellonella larvae as a model to assess virulence of S. suis strains.ResultsFourteen isolates of S. suis belonging to different serotypes killed G. mellonella larvae in a dose-dependent manner. Larvae infected with the virulent serotype 2 strain, S. suis S3881/S10, were rescued by antibiotic therapy. Crucially, the observed virulence of the different serotypes and mutants was in agreement with virulence observed in piglets (Sus scrofa) and the zebrafish larval infection model. Infection with heat-inactivated bacteria or bacteria-free culture supernatants showed that in most cases live bacteria are needed to cause mortality in G. mellonella.ConclusionsThe G. mellonella model is simple, cost-efficient, and raises less ethical issues than experiments on vertebrates and reduces infrastructure requirements. Furthermore, it allows experiments to be performed at the host temperature (37 °C). The results reported here, indicate that the G. mellonella model may aid our understanding of veterinary microbial pathogens such as the emerging zoonotic pathogen S. suis and generate hypotheses for testing in the target animal host. Ultimately, this might lead to the timely introduction of new effective remedies for infectious diseases. Last but not least, use of the G. mellonella infection model to study S. suis virulence adheres to the principles of replacement, reduction and refinement (3Rs) and can potentially reduce the number of vertebrates used for experimental infection studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0905-2) contains supplementary material, which is available to authorized users.

New Perspectives on Galleria mellonella Larvae as a Host Model Using Riemerella anatipestifer as a Proof of Concept

“…Evidence accumulated in recent years has demonstrated that G. mellonella larvae can be used as an attractive alternative model to identify the virulence of various pathogens (42,(47)(48)(49)(50). In this study, we investigated the extent to which the virulence factors required for pathogenesis in both ducklings and G. mellonella larvae overlap.…”

“…Regardless, these results indicate that R. anatipestifer can use iron from larvae during colonization and infection under iron-limiting conditions, which is similar to the case in the vertebrate host. Since other bacteria, such as Listeria monocytogenes (48), Streptococcus (49), and Escherichia coli (11), were also able to proliferate inside G. mellonella larvae, it was suggested that other infective bacteria were able to get the iron source from them.…”

ClpP participates in stress tolerance, biofilm formation, antimicrobial tolerance, and virulence of Enterococcus faecalis

“…Virulence of E. faecalis in G. mellonella Infection of G. mellonella larvae with E. faecalis strains was performed as described previously for other pathogens [51]. G. mellonella larvae in groups of 40 were infected in the left posterior proleg with 20 μL inocula of E. faecalis strains containing 5 × 10 6 CFU/mL.…”

Galleria mellonellaas an infection model for the multi-host pathogenStreptococcus agalactiaereflects hypervirulence of ST283

“…They have also been use to study the virulence of other Streptococcus spp. : Streptococcus pyogenes 29,30 , Streptococcus pneumonia 31 , Streptococcus suis 32 . Their ease of use, short life span and cost effectiveness make them a useful tool for screening of new antimicrobials and pathogen mutant libraries 33,34 .…”

“…However, some virulence factor (e.g. the lactose operon in bovine isolates) would not be reflected in a Galleria model and although correlation between the results obtained in the G. mellonella larvae model and other animal models have been shown for several pathogens30,32 , disparity in the importance of virulence factors in different hosts has also been demonstrated36 , highlighting the need for caution when searching for the impact of specific virulence factors in this model. Unlike other invertebrate models such as Caenorhabditis elegans and Drosophila melanogaster, G. mellonella larvae are able to survive at 37°C and 28°C, enabling the study of GBS infection in the range of relevant host-specific temperatures.…”