Abstract
Galleria mellonella is a recognised model to study antimicrobial efficacy; however, standardisation across the scientific field and investigations of methodological components are needed. Here, we investigate the impact of weight on mortality following infection with Methicillin-resistant Staphylococcus aureus (MRSA). Larvae were separated into six weight groups (180-300mg at 20mg intervals) and infected with a range of doses of MRSA to determine the 50% lethal dose (LD50), and the 'lipid weight' of larvae post-infection was quantified. A model of LD50 values correlated with weight was developed. The LD50 values, as estimated by our model, were further tested in vivo to prove our model. We establish a weight-dependent LD50 in larvae against MRSA and demonstrate that G. mellonella is a stable model within 180-260mg. We present multiple linear models correlating weight with: LD50, lipid weight, and larval length. We demonstrate that the lipid weight is reduced as a result of MRSA infection, identifying a potentially new measure in which to understand the immune response. Finally, we demonstrate that larval length can be a reasonable proxy for weight. Refining the methodologies in which to handle and design experiments involving G. mellonella, we can improve the reliability of this powerful model.
Highlights
Galleria mellonella (Greater wax moth) larvae are widely utilised for toxicity screening (Desbois and Coote 2012; Maguire, Duggan and Kavanagh 2016; Coates et al 2019) and to study host-pathogen interactions (Peleg et al 2009; Olsen et al.2011; Junqueira 2012; Wojda and Taszłow 2013)
To begin testing our hypothesis, LD50 values were determined for each weight group
A sigmoidal non-linear model best fit the dose-dependent response of the data, resulting in an LD50 calculated for each weight group (Fig. 2)
Summary
Galleria mellonella (Greater wax moth) larvae are widely utilised for toxicity screening (Desbois and Coote 2012; Maguire, Duggan and Kavanagh 2016; Coates et al 2019) and to study host-pathogen interactions (Peleg et al 2009; Olsen et al.2011; Junqueira 2012; Wojda and Taszłow 2013). Mellonella can be incubated at 37°C, which facilitates the investigation of human pathogens This has included most of the ESKAPE pathogens: Enterococcus faecium (Chibebe Junior et al 2013; Luther et al 2014); Staphylococcus aureus (Brackman et al 2011; Ramarao, Nielsen-Leroux and Lereclus 2012; Sheehan, Dixon and Kavanagh 2019); Klebsiella pneumoniae A positive correlation between the virulence and immune responses between mammalian models and G. mellonella has been established for P. aeruginosa (Jander, Rahme and Ausubel 2000), Cryptococcus neoformans (Mylonakis et al.2005), and S. aureus (Sheehan, Dixon and Kavanagh 2019), demonstrating the powerful potential of this invertebrate model.
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