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Microbiology JoVE (Open Access) Citable · DOI

Detection of Foodborne Bacterial Pathogens from Individual Filth Flies

DOI: 10.3791/52372-v
What you'll learn
  • ✓ Dissect wild-caught flies to extract bacterial samples from body surfaces and alimentary canals
  • ✓ Perform PCR-based detection of Cronobacter, Salmonella, and Listeria from insect samples
  • ✓ Isolate and culture foodborne pathogens from PCR-positive fly samples
  • ✓ Apply environmental sampling protocols during foodborne outbreak investigations
Protocol

A PCR-based protocol was adapted to detect Cronobacter spp., Salmonella enterica, and Listeria monocytogenes from body surfaces and alimentary canals of individual wild-caught flies. The goal of this protocol is to detect and isolate bacterial pathogens from individual insects collected as part of an environmental sampling program during foodborne outbreak investigations.

Difficulty
intermediate
Total time
~4–6 hours per batch of 10–20 flies (dissection ~1 hr, enrichment overnight, PCR ~2 hrs, isolation ~1–2 hrs)
Biosafety
BSL-2

Steps

1
Dissect flies and enrich bacterial cultures

Dissect individual wild-caught flies to separate body surfaces and alimentary canals, then place tissues in enrichment media to recover target foodborne pathogens. Incubate overnight to allow bacterial amplification.

▶ 02:36
2
Lyse enriched samples for pathogen detection

Prepare lysates from enriched fly samples using lysis buffer to release bacterial DNA. This step prepares the sample for downstream PCR-based pathogen detection.

▶ 06:27
3
Perform PCR detection of target pathogens

Run species-specific PCR assays on lysed samples to detect Cronobacter spp., Salmonella enterica, and Listeria monocytogenes. Analyze results by gel electrophoresis or real-time PCR.

▶ 07:27
4
Isolate bacteria from positive PCR results

Culture bacteria from PCR-positive samples on selective media to obtain pure isolates for further characterization and confirmation of pathogenic species.

▶ 08:30
5
Analyze prevalence of pathogens in wild flies

Summarize detection results across fly samples collected during environmental surveillance, reporting prevalence rates of Cronobacter, Salmonella, and Listeria in wild populations.

▶ 10:38
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