The Impact of Multiple Infections within Drosophila melanogaster

Primary infections in Drosophila melanogaster provide protection against secondary more lethal infections through both increased resistance and increased tolerance.

Five day old flies were injected in the abdomen with either Phosphate buffered saline (PBS, control), Enterococcus faecalis, or Serratia marcescens to establish chronic infections. After one week flies were injected in the thorax with a range of doses of Providencia rettgeri to establish lethal infections. Results showed statistically significant protection of flies given E. faecalis or S. marcescens at the primary injection over flies that had only received the control. Survival curves were plotted against bacterial loads and there was both improved resistance, shown by lower loads in doubly infected flies, and improved tolerance, shown by a less steep slope.