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Detection of Foodborne Bacterial Pathogens from Individual Filth Flies
Published on: February 13, 2015
Isolation of Enterobacter sakazakii from stable flies, Stomoxys calcitrans L. (Diptera: Muscidae)
1Department of Entomology, Kansas State University, Manhattan, Kansas 66506, USA.
Insights
Stable flies (Stomoxys calcitrans) rarely carry the foodborne pathogen Enterobacter sakazakii. This study suggests animal manure, not flies, is the primary reservoir for this dangerous bacterium.
Area of Science:
- Food safety
- Microbiology
- Veterinary entomology
Background:
- Enterobacter sakazakii is an opportunistic foodborne pathogen causing severe infections in infants.
- Stable flies (Stomoxys calcitrans) were previously suspected as potential vectors or reservoirs for E. sakazakii.
Purpose of the Study:
- To investigate the prevalence of Enterobacter sakazakii in stable flies.
- To determine if stable flies act as a significant reservoir or vector for E. sakazakii.
Main Methods:
- Culturing techniques and 16S rDNA PCR-restriction fragment length polymorphism genotyping and sequencing were used.
- 928 individual stable flies from Kansas and Florida were screened for E. sakazakii and other enteric bacteria.
Main Results:
- Only two stable flies (0.2%) tested positive for E. sakazakii.
- A significant proportion of flies carried other enteric bacteria, including Escherichia and Enterobacter species, commonly found in animal manure.
- The prevalence of E. sakazakii in stable flies was very low.
Conclusions:
- Stable flies are unlikely to be a major reservoir or vector for Enterobacter sakazakii.
- The findings indicate that the natural reservoir for E. sakazakii is likely the digestive tract or manure of domestic animals.
Abstract:
Enterobacter sakazakii is an opportunistic foodborne pathogen that causes meningitis, enterocolitis, and sepsis, primarily in immunocompromised infants. Previously, it was suggested that stable flies, Stomoxys calcitrans, were a vector or reservoir of this pathogen. In our study, by means of a culturing approach combined with 16S rDNA PCR-restriction fragment length polymorphism genotyping and sequencing, we screened 928 individual stable flies collected in Kansas and Florida. Two stable flies (0.2%) were positive for E. sakazakii. In addition, 411 (44%) stable flies carried bacteria-forming red colonies (presumably enterics) on a violet red bile glucose agar (mean count = 6.4 x 10(4) CFU per fly), and 120 (13%) stable flies carried fecal coliforms (mean count = 8.7 X 10(3) CFU per fly). Sequencing of 16S rDNA showed that enterics from violet red bile glucose agar were represented by several genera, including Escherichia, Shigella, Providencia, Enterobacter, Pantoea, Proteus, Serratia, and Morganella. Our study shows that stable flies carry bacteria typically present in animal manure (a developmental site of stable fly larvae), which indicates that the natural reservoir of E. sakazakii is the digestive tract or manure of domestic animals. The low prevalence of E. sakazakii associated with stable flies suggests that stable flies do not play a major role as a reservoir or vector of this pathogen.
