Galleria mellonella infection models for the study of bacterial diseases and for antimicrobial drug testing

Abstract

Galleria mellonella (greater wax moth or honeycomb moth) has been introduced as an alternative model to study microbial infections. G. mellonella larvae can be easily and inexpensively obtained in large numbers and are simple to use as they don't require special lab equipment. There are no ethical constraints and their short life cycle makes them ideal for large-scale studies. Although insects lack an adaptive immune response, their innate immune response shows remarkable similarities with the immune response in vertebrates. This review gives a current update of what is known about the immune system of G. mellonella and provides an extensive overview of how G. mellonella is used to study the virulence of Gram-positive and Gram-negative bacteria. In addition, the use of G. mellonella to evaluate the efficacy of antimicrobial agents and experimental phage therapy are also discussed. The review concludes with a critical assessment of the current limitatons of G. mellonella infection models.

Keywords: Galleria mellonella; Gram-negative pathogens; Gram-positive pathogens; antimicrobial drug testing; infection model; innate immunity; wax worm.

Figure 1.

Photographic images of G. mellonella larvae. A: Image of a healthy G. mellonella last instar larvae with a typical creamy color and a size of 2 to 2.5 cm. B: Images of infected larvae showing different stages of disease. Melanization, which comprises the synthesis and deposition of melanin to encapsulate pathogens at the wound site followed by hemolymph coagulation and opsonization typically starts with distinctive black spots on the cream colored larvae (third image from left). Complete melanization (black larvae, left image) correlates with death of the larvae soon after. A decrease in cocoon formation can also be used as a marker for disease in G. mellonella larvae (right image) The numbers on the bottom of Fig. 1B are the health index scores (see also Table 2).