Listeria monocytogenes is a highly diverse species, exhibiting differential virulence potential within
strains from different clonal complexes (CCs). Hypervirulent CCs strains tend to be associated with
higher frequency in clinical cases and severe outcomes, while hypovirulent CCs are characterized
by a reduced level of virulence and are often associated with food-related contamination. Recently,
researchers have employed Galleria mellonella larvae as an in vivo model to characterize these
variable virulence patterns among Listeria strains. Although it has only been utilized once to study
CC-related virulence thus, there is still uncertainty about its relevance as an in vivo model. Infection
studies with G. mellonella larvae were performed to evaluate the virulence potential of 16 Lm strains
from CC1, CC2, CC4, CC6, CC388, CC87, CC9 and CC121. Hence, the survival rate and health
index scores of larvae were used to quantify the virulence capacity of this pathogen. Results
obtained indicate that: the CC2 strain exhibited a hypovirulent phenotype in the larvae with the
highest survival rate and health index scores, followed by two strains from CC1 and CC6. In
contrast, another CC6 strain exhibited reduced larvae survival rates, followed by the CC4 strain.
Furthermore, strains from CC9, which is considered hypovirulent, caused around 47% mortality
(Figure 1). Our findings revealed clear variations in virulence patterns that were previously
determined with other in vitro and in vivo models. Moreover, it was observed a strain-dependent
intra-clonal complex virulence difference in the infection of G. mellonella larvae. Additionally, by
eliminating the dependence of L. monocytogenes strains on the inlA gene for host cell invasion, it
was observed that hypovirulent clones demonstrated an infection potential equal to or greater than
that of hypervirulent strains. Hence, there are still virulence markers that need to be characterized
to improve the genotypic distinction of these CCs.This work was supported by National Funds from FCT - Fundação para a Ciência e a Tecnologia through project GenoPhenoTraits4Persitence - Genomic and phenotypic traits contributing to persistence of Listeria monocytogenes in food processing environment (PTDC/BAAAGR/4194/2021).info:eu-repo/semantics/publishedVersio
