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Published on: February 13, 2015
Significance and survival of Enterococci during the house fly development
Anuradha Ghosh1, Mastura Akhtar2, Chris Holderman2
1Department of Diagnostic Medicine and Pathobiology, Kansas State University, 221K Mosier Hall, Manhattan, KS 66506, USA.
Abstract:
House flies are among the most important nonbiting insect pests of medical and veterinary importance. Larvae develop in decaying organic substrates and their survival strictly depends on an active microbial community. House flies have been implicated in the ecology and transmission of enterococci, including multi-antibiotic-resistant and virulent strains of Enterococcus faecalis. In this study, eight American Type Culture Collection type strains of enterococci including Enterococcus avium, Enterococcus casseliflavus, Enterococcus durans, Enterococcus hirae, Enterococcus mundtii, Enterococcus gallinarum, Enterococcusfaecalis, and Enterococcusfaecium were evaluated for their significance in the development of house flies from eggs to adults in bacterial feeding assays. Furthermore, the bacterial colonization of the gut of teneral flies as well as the importance of several virulence traits of E. faecalis in larval mortality was assessed. Overall survival of house flies (egg to adult) was significantly higher when grown with typically nonpathogenic enterococcal species such as E. hirae (76.0% survival), E. durans (64.0%), and E. avium (64.0%) compared with that with clinically important species E. faecalis (24.0%) and E. faecium (36.0%). However, no significant differences in survival of house fly larvae were detected when grown with E. faecalis strains carrying various virulence traits, including isogenic mutants of the human clinical isolate E. faecalis V583 with in-frame deletions of gelatinase, serine protease, and capsular polysaccharide serotype C. Enterococci were commonly detected in fly puparia (range: 75-100%; concentration: 103-105 CFU/puparium);however, the prevalence of enterococci in teneral flies varied greatly: from 25.0 (E. casseliflavus) to 89.5% (E. hirae). In conclusion, depending on the species, enterococci variably support house fly larval development and colonize the gut of teneral adults. The human pathogenic species, E. faecalis and E. faecium, poorly support larval development and are likely acquired in nature by adult flies during feeding. House fly larvae do not appear to be a suitable model organism for assessment of enterococcal virulence traits.
Insights
House flies develop better with nonpathogenic enterococci than pathogenic ones. Virulence traits of Enterococcus faecalis did not affect house fly larval survival, suggesting flies acquire these bacteria from adult feeding.
Area of Science:
- Medical entomology
- Microbiology
- Insect-microbe interactions
Background:
- House flies are significant pests in medical and veterinary fields.
- Their larval development relies on microbial communities in decaying matter.
- Enterococci, including pathogenic strains like Enterococcus faecalis, are associated with house flies.
Purpose of the Study:
- To evaluate the impact of different enterococcal species on house fly development.
- To assess gut colonization of adult flies by enterococci.
- To determine the role of Enterococcus faecalis virulence factors in larval mortality.
Main Methods:
- Bacterial feeding assays using eight American Type Culture Collection enterococcal strains.
- Evaluation of house fly survival from egg to adult.
- Analysis of enterococcal gut colonization in teneral flies and puparia.
- Assessment of Enterococcus faecalis virulence traits' effect on larval mortality.
Main Results:
- House fly survival was significantly higher with nonpathogenic species (e.g., E. hirae, E. durans, E. avium) compared to pathogenic ones (E. faecalis, E. faecium).
- Enterococcus faecalis virulence traits did not influence house fly larval survival.
- Enterococci were prevalent in puparia (75-100%), but teneral fly colonization varied widely (25-89.5%).
Conclusions:
- Enterococci species differentially support house fly larval development and gut colonization.
- Pathogenic Enterococcus faecalis and E. faecium poorly support larval development, suggesting adult acquisition.
- House fly larvae are not suitable models for assessing enterococcal virulence traits.
