SOP: Campylobacter Detection in Poultry

Campylobacter is the leading bacterial cause of foodborne illness in many countries, and poultry is its main vehicle. It needs low oxygen and body temperature to grow, which is exactly what the microaerophilic incubation provides. Testing raw poultry for it is routine in many markets.

Microbiological testing protects consumers from pathogens and tracks hygiene across the plant. Because living organisms are the analyte, aseptic technique and precise incubation conditions are not optional extras; they are the measurement itself. A single lapse in sterility or temperature control invalidates the result.

Purpose

To detect Campylobacter jejuni and Campylobacter coli in poultry by microaerophilic enrichment and selective plating.

Scope

Applies to raw poultry meat, carcasses rinses, and processing environment samples.

Equipment and Materials

• Bolton broth or Preston broth for enrichment
• Modified charcoal cefoperazone deoxycholate (mCCDA) agar
• Microaerophilic gas packs or tri-gas incubator (5 percent O2, 10 percent CO2, 85 percent N2)
• Incubator at 41.5 C
• Confirmation: oxidase, hippurate hydrolysis, or validated PCR
• Stomacher, sterile bags

Procedure

1. Weigh 25 g of sample into a sterile bag, add 225 mL of Bolton broth, and stomach briefly (30 seconds) to avoid damaging the fragile cells.
2. Incubate microaerophilically at 37 C for 4 hours (resuscitation), then at 41.5 C for 44 hours.
3. Streak onto mCCDA plates and incubate microaerophilically at 41.5 C for 44 hours.
4. Typical colonies are grey, flat, and spreading, sometimes with a metallic sheen.
5. Confirm suspect colonies: oxidase positive, characteristic curved rods on Gram stain, hippurate positive for C. jejuni.
6. Report as detected or not detected in 25 g.

Recording Results

Report detection with the confirmation method. Record gas conditions and incubation temperatures precisely; Campylobacter is unforgiving of deviations.

Quality Control

Verify each new lot of culture media with reference strains before use: the target organism must show typical growth and morphology, and a non-target strain must be inhibited or show atypical growth as expected. Include a positive control (reference strain) and a negative control (sterile diluent) with every test batch. Incubate an uninoculated plate from each poured batch as a sterility check. Monitor incubator temperatures twice daily with a calibrated thermometer; do not use incubators found outside tolerance until corrected and re-verified. Track contamination rates in blanks; a rising blank contamination rate signals a systemic problem requiring investigation. Participate in proficiency testing at least annually and investigate any unsatisfactory scores with documented corrective action.

Troubleshooting

• No growth: oxygen exposure killed the cells. Minimize air exposure and verify the microaerophilic atmosphere with indicator strips.
• Overgrowth by competitors: enrichment temperature low. Verify 41.5 C calibration.
• Atypical colonies: confirm by PCR; morphology alone is unreliable for some strains.
• Incubator temperature alarm overnight: assess all plates incubated during the excursion; document the impact decision and repeat affected tests.
• Reference strain atypical: the culture may have mutated or been mislabeled. Obtain a fresh certified strain and re-verify media.

Interferences and Limitations

Injured or stressed cells may fail to grow on selective media, causing false negatives; the resuscitation steps in this procedure address this but cannot recover all injured populations. Viable-but-nonculturable organisms are not detected by culture methods. High background flora can mask target colonies on plating media, which is why confirmation of suspect colonies is mandatory rather than optional. Antimicrobial residues in the sample (sanitizers, preservatives) suppress growth and must be neutralized during homogenization. Results apply to the analytical unit tested; heterogeneous contamination requires larger or composite sampling plans.

Safety Notes

• Campylobacter is Biosafety Level 2 and highly infectious at low doses. Strict aseptic technique in the cabinet.
• Autoclave all enrichments and plates.
• Disinfect spills immediately; the organism survives poorly outside the host but the infectious dose is tiny.