Limitations in the use of Drosophila melanogaster as a model host for gram-positive bacterial infection

Abstract

Aims: To examine sensitivities of various Drosophila melanogaster strains towards human pathogenic and nonpathogenic gram‐positive bacteria. Methods and Results: The D. melanogaster Oregon R strain was infected by injecting the thorax with a needle containing Escherichia coli (negative control), Listeria monocytogenes, Staphylococcus aureus (both food‐borne pathogens), Listeria innocua, Bacillus subtilis, Carnobacterium maltaromaticum, Lactobacillus plantarum or Pediococcus acidilactici (all nonpathogenic bacteria). Listeria monocytogenes and S. aureus killed the host rapidly compared with the negative control. Infection with L. innocua, B. subtilis or C. maltaromaticum also resulted in a high fly mortality, whereas Lact. plantarum and P. acidilactici resulted in a slightly increased mortality. Four additional D. melanogaster lines, three of which had been selected for heat, cold and desiccation resistance respectively, were subjected to infection by L. monocytogenes, S. aureus and E. coli. Mortality rates were comparable with that of the Oregon R strain. Conclusions: Use of the injection method shows the limitation of D. melanogaster as a model host for gram‐positive bacteria as opportunistic infection by nonpathogenic gram‐positive bacteria results in partial or high mortality. In addition, lines of fruit flies resistant to various stress exposures did not show an increased resistance to infection by gram‐positive pathogens under the conditions tested. Significance and Impact of the Study: This study demonstrates the inadequacy of D. melanogaster infected by the injection method in order to distinguish between virulent and nonvirulent gram‐positive bacteria.

Drosophila melanogaster NPC2 proteins bind bacterial cell wall components and may function in immune signal pathways

“…Larvae were then collected at 0, 2, 6, 12, and 24h after feeding for total RNA extraction, and each group contained at least 15 larvae. For infection experiments in adult flies, E. coli culture was diluted to OD 600 =0.8 (Jensen, 2007), and S. aureus culture was diluted to OD 600 =0.2 (Nehme, 2011). Female and male adult flies (2–4 days old) were pricked at the dorsal thorax with glass needles dipped in the diluted E. coli or S. aureus culture, or PBS (control).…”

Chitin Hydrolysis by Listeria spp., Including L. monocytogenes

“…A note of caution toward this hypothesis is offered, however, by the scarcity of reports on the presence of Listeria in arthropods even though several other Firmicutes, including Bacillus, Clostridium, Enterococcus, and Lactococcus, are frequently isolated from this habitat (1, 2, 7, 13). L. monocytogenes, including the EGD strain, has been shown to exert virulence toward Drosophila melanogaster (14,20). This effect cannot, however, be attributed to chitinolytic activity as infection was established by injection of bacterial cells into the thorax, thereby bypassing the first natural step of infection, including entry of the pathogen over the chitin-containing cuticle.…”

Illuminating the landscape of host–pathogen interactions with the bacterium Listeria monocytogenes

“…Use of this insect allowed to distinguish between pathogenic and nonpathogenic Listeria species and to discriminate between L. monocytogenes serotypes exhibiting attenuated virulence properties. In the main insect model Drosophila, there seems to be little contribution of Listeria virulence factors to septic infection, and a recent study described some limitations of Drosophila melanogaster as a heterologous host for the study of several Gram-positive bacteria (120). Importantly, flies are not maintained at 37°C, preventing studies at a temperature close to that of infected mammals.…”