Pre-Exposure to α-Linolenic Acid Reduces Virulence of Cronobacter sakazakii in Galleria mellonella Infection Model

Abstract

Cronobacter sakazakii is a food-borne pathogen with infections notifiable in those under 12 months old. Current inhibition methods rely on manufacture and reconstitution guidelines. Fatty acids (FA) are a possible method of control, with reports showing FAs can be bactericidal and regulate virulence mechanisms such as biofilm formation. This research explores the efficacy of the long-chain FA α-linolenic (ALA) to reduce C. sakazakii virulence in vivo. Galleria mellonella larvae were injected with FA pre-treated C. sakazakii and viability monitored every 24 h over a total of 96 h. To show the interaction between the host immune system and C. sakazakii, haemocytes and bacterial cells were mixed and enumerated following incubation. To investigate the impact on antimicrobial resistance (AMR), 24 antibiotics were tested against C. sakazakii pretreated with ALA. Kaplan–Meier survival curves generated showed a dose-dependent increase in larval survival upon increased FA concentration. Regarding the immune evasion assay, data generated show increased C. sakazakii and decreased haemocyte counts in the same sample. From the AMR results, there was no statistically significant difference in inhibition zones when compared to the control, indicating no contraindications for current treatment options. α-linolenic acid is a common component of the human diet and is shown here to directly reduce virulence mechanisms including immune system evasion. Pre-treatment with ALA reduces the virulence of C. sakazakii, resulting in increased survival of G. mellonella larvae. This suggests that ALA may serve as a candidate for further evaluation as a potential agent against C. sakazakii.