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Vector competence of stable flies, Stomoxys calcitrans L. (Diptera: Muscidae), for Enterobacter sakazakii
1Department of Entomology, Kansas State University, Manhattan, KS 66506, USA.
Insights
Stable flies (SF) can carry the food-borne pathogen Enterobacter sakazakii for over 20 days, potentially contaminating food sources. This pathogen also supports SF development and colonizes their digestive tracts.
Area of Science:
- Medical entomology
- Food safety
- Microbiology
Background:
- Enterobacter sakazakii is an opportunistic food-borne pathogen linked to severe infant infections.
- Stable flies (Stomoxys calcitrans L.) are suspected vectors and reservoirs of E. sakazakii.
Purpose of the Study:
- To evaluate the vector competence of adult stable flies for E. sakazakii.
- To determine the effect of E. sakazakii on stable fly development.
- To assess the survival and gut colonization of E. sakazakii during stable fly development.
Main Methods:
- Adult stable flies were fed blood or sugar contaminated with E. sakazakii.
- Larval development and survival were assessed in sterilized cattle manure and artificial medium inoculated with E. sakazakii.
- Pathogen presence in adult flies and substrate was quantified using CFU counts and prevalence.
Main Results:
- Adult stable flies maintained E. sakazakii for at least 20 days, contaminating food sources (1.8 x 10^5 to 6.4 x 10^6 CFU/fly).
- E. sakazakii supported immature stable fly development in sterilized media (76.7-78.3% survival).
- E. sakazakii colonized the gut of emerging adult flies (12.8-21.7% prevalence) when reared in sterile conditions, but not in non-sterilized manure.
Conclusions:
- Adult stable flies can act as long-term carriers of E. sakazakii.
- E. sakazakii can support stable fly development and survive pupation.
- Gut colonization of newly-emerged flies suggests potential for pathogen transmission, particularly in controlled environments.
Abstract:
Enterobacter sakazakii is an opportunistic food-borne pathogen causing meningitis, enterocolitis, and sepsis, primarily in immunocompromised infants. It has been suggested that stable flies, Stomoxys calcitrans L., are a vector/reservoir of this pathogen. In this study, we assessed a) vector competence of adult stable flies (SF) for E. sakazakii, b) effect of E. sakazakii on SF development, and c) survival of E. sakazakii during SF development and colonization of the digestive tract of newly-emerged flies. Our data show that in the colony, adult SF can maintain E. sakazakii for at least 20 days regardless of the food source (blood or sugar) and contaminate the food source. The concentration of the pathogen per individual SF ranged from 1.8 x 10(5) to 6.4 x 10(6) CFU. E. sakazakii supported development of immature SF in sterilized cattle manure and sterilized artificial medium (78.3% and 76.7% SF survival to adult stage, respectively). In addition, E. sakazakii survived during SF development and colonized the gut of emerging adult SF but only when SF larvae were maintained on sterilized cattle manure inoculated with E. sakazakii (12.8% prevalence in adult SF) and on the sterile artificial medium with E. sakazakii (21.7% prevalence in adult SF). E. sakazakii was not recovered from flies or the substrate when larvae were reared on cattle manure with a non-sterilized complex microbial community plus the E. sakazakii inoculum. This study shows that SF adults have a potential to carry E. sakazakii for an extended period of time. E. sakazakii supports SF development and can survive during SF pupation and then colonize the gut of newly-emerged flies.
