Galleria mellonella Infection Model Demonstrates High Lethality of ST69 and ST127 Uropathogenic E. coli

Abstract

Galleria mellonella larvae are an alternative in vivo model for investigating bacterial pathogenicity. Here, we examined the pathogenicity of 71 isolates from five leading uropathogenic E. coli (UPEC) lineages using G. mellonella larvae. Larvae were challenged with a range of inoculum doses to determine the 50% lethal dose (LD50) and for analysis of survival outcome using Kaplan-Meier plots. Virulence was correlated with carriage of a panel of 29 virulence factors (VF). Larvae inoculated with ST69 and ST127 isolates (104 colony-forming units/larvae) showed significantly higher mortality rates than those infected with ST73, ST95 and ST131 isolates, killing 50% of the larvae within 24 hours. Interestingly, ST131 isolates were the least virulent. We observed that ST127 isolates are significantly associated with a higher VF-score than isolates of all other STs tested (P≤0.0001), including ST69 (P<0.02), but one ST127 isolate (strain EC18) was avirulent. Comparative genomic analyses with virulent ST127 strains revealed an IS1 mediated deletion in the O-antigen cluster in strain EC18, which is likely to explain the lack of virulence in the larvae infection model. Virulence in the larvae was not correlated with serotype or phylogenetic group. This study illustrates that G. mellonella are an excellent tool for investigation of the virulence of UPEC strains. The findings also support our suggestion that the incidence of ST127 strains should be monitored, as these isolates have not yet been widely reported, but they clearly have a pathogenic potential greater than that of more widely recognised clones, including ST73, ST95 or ST131.

Highly diverse and antimicrobial susceptible Escherichia coli display a naïve bacterial population in fruit bats from the Republic of Congo

“…Additionally, ST69, ST101 and ST127 also predominantly consist of human ExPEC strains and have been associated with severe disease [82–85]. However, the virulence features of the isolated strains were much less pronounced, indicating these particular strains of STs as being less virulent compared to their counterparts circulating in the human population.…”

Strengths and Limitations of Model Systems for the Study of Urinary Tract Infections and Related Pathologies

“…Such conservation of function means that information gleaned by analysis of UPEC-associated fitness and virulence factors within one model system may be relevant in other environments. Consequently, the use of surrogate hosts like C. elegans and zebrafish, or even larvae of the wax moth Galleria mellonella (250)(251)(252), is not so tangential to UTI research and has the potential to drive important discoveries in human patients. Findings made by using animal model systems can be complemented and extended in broth culture or on agar plates using genetic and biochemical assays that are designed to examine how UPEC mutants and wild-type strains handle specific stresses such as reactive oxygen species or serum components like complement (197,243).…”

Using Galleria mellonella as an In Vivo Model to Study the Virulence of Some Bacterial and Fungal Agents

“…Son yıllarda sağlık hizmeti ile ilişkili enfeksiyonlar arasında en büyük sorunu oluşturan dirençli Acinetobacter kö- kenlerinden birinin 16 saatlik modelde mortalite oranı, diğer gram-negatif bakteriler ile oluşturulan enfeksiyonlardan daha düşük bulunmuştur. Bu bakteriler ile yapılan benzer çalışmalarda da virülansın antibiyotik direncinden bağımsız olduğu gösterilmiştir [10][11][12][13] . Bu sonuçlar, bakterilerde virülansın antibiyotik direncinden ayrı değerlendirilmesi gerektiğini düşündürmektedir.…”