A specimen begins to change as soon as it leaves the patient or collection site. Bordet GENGOU Agar (Sheep Blood 15%) Culture Media is therefore a pre-analytical control, not simply a container. The discussion below connects its documented role with preparation variables, controls, interpretation, and the limits of inference. Catalogue 10353 is discussed as a laboratory measurement component; implementation should follow the laboratory SOP and validated reference method.
Analytical scope and method role
Bordet Gengou Agar (Sheep blood 15%) is a selective medium for the isolation of Bordetella spp., including B. pertussis and B. parapertussis.
Method principle
Potato infusion, peptic digest of animal tissue and pancreatic digest of casein provide amino acids, nitrogen and vitamins for organisms growth. Glycerol is a source of carbon. Yeast extract is a source of vitamins, particularly of B-group. Sodium chloride maintains the osmotic balance of the medium. Agar is the solidifying agent. Cefalexin partially suppresses normal respiratory tract flora. Sheep blood provides essential growth factors for recovery and cultivation of Bordetella spp.
Formula and functional interpretation
(per litre of purified water)Potato Infusion 4.5 gPeptic Digest of Animal Tissue 5.0 gPancreatic Digest of Casein 5.0 gSodium Chloride 5.5 gAgar 16.0 gCefalexin 0.04 gGlycerol 10 mlSheep Blood, defibrinated150 mlFinal pH 6.7 ± 0.2
Review the nutritive, selective, differential, buffering, reducing, and indicator components against the expected target and background flora. Preparation errors can change recovery, inhibition, colour development, or endpoint visibility even when incubation is correct.
Preparation and execution: controlled method points
Procedure: Inoculate the plates as soon as possible after the arrival of the specimens(*) in the laboratory and streak for dilution. Incubate in ambientair in a moist chamber at 35 ± 2°C for 7-10 days, and inspect daily, using a magnifying lens.(*) Consult appropriate
Translate the method into controlled worksheet fields: catalogue and lot, preparation mass or volume, water quality, pH where applicable, heating or sterilization, supplements, dispense volume, preparation date, expiry assignment, incubation atmosphere and temperature, reading window, equipment, and analyst. Record departures as deviations instead of silently normalizing them.
Quality control: what the control result protects
Challenge both sides of performance. Include a target reaction demonstrating recovery and, when relevant, a non-target or alternate reaction challenging inhibition or differentiation. Record expected and observed responses, acceptance criteria, strain and passage, lot, incubation, and disposition. A failed control blocks result interpretation until the cause is resolved.
Interpretation and confirmation pathway
Colonies of Bordetella pertussis appear small, white, domed and glistening, resembling bisected pearls and may be surrounded by a weak beta-hemolysis.
Record the raw observation before the conclusion: morphology or colour, growth pattern, endpoint, reaction intensity, reading time, and control response. Presumptive reactions remain presumptive. Route atypical, weak, mixed, or delayed reactions through the confirmation step in the current method.
Limitations and boundaries of use
Applicability depends on matrix, target organism, interfering flora, inoculum, validated method, and regulatory setting. Do not transfer conditions or acceptance criteria from a different matrix without verification.
Troubleshooting from evidence, not guesswork
- Poor recovery: check preparation, pH, overheating, supplement addition, inoculum, atmosphere, storage, and control performance.
- Loss of selectivity: review formulation, sterilization, expiry, inoculum burden, enrichment sequence, and incubation time.
- Weak or atypical reaction: confirm reading time and atmosphere, compare controls, document mixed growth, and follow confirmation requirements.
- Run-to-run drift: trend lot, analyst, equipment, water, preparation batch, controls, and environmental conditions.
External method context
The product should be understood as one measurement component in an antimicrobial susceptibility method. The analytical chain includes isolate purity, standardized inoculum, medium composition, antimicrobial concentration, incubation atmosphere and time, endpoint reading, and the interpretive table selected by the laboratory. A shift in any upstream variable can move an MIC or zone without a change in organism biology, which is why QC distributions and trend review are more informative than a single pass/fail control.
External laboratory-quality guidance also supports a lifecycle view: verify the method when introduced, bridge new lots against an accepted lot, trend control results, investigate nonconformities, and retain enough raw observations to reconstruct the decision. This is the practical difference between reproducing a preparation instruction and demonstrating that the resulting measurement is fit for its intended use.
EUCAST disk diffusion and quality control
EUCAST requires standardized methodology, current breakpoint tables, and routine quality control; the laboratory remains responsible for the final susceptibility report. For broth dilution, inoculum density, cation content, pH, incubation atmosphere, endpoint definition, and two-fold dilution design influence MIC reproducibility. Breakpoints are interpretive rules applied after a technically valid MIC or zone measurement; they are not properties of the product alone. Review the authoritative source.
FDA Bacteriological Analytical Manual
FDA BAM methods organize food microbiology around validated sampling, preparation, enrichment, isolation, and confirmation steps, with method applicability tied to the matrix and target organism. Sampling uncertainty, homogenization efficiency, inhibitory ingredients, dilution design, and countable range can dominate the result before the culture medium is ever inoculated; those variables belong in method verification and uncertainty review. Review the authoritative source.
WHO Laboratory Quality Management System handbook
WHO laboratory quality guidance treats document control, equipment, purchasing and inventory, process control, records, occurrence management, and continual improvement as connected parts of reliable testing. Review the authoritative source.
Technical references
- Manufacturer product documentation for catalogue 10353.
- EUCAST disk diffusion and quality control (access checked 2026-07-20).
- FDA Bacteriological Analytical Manual (access checked 2026-07-20).
- WHO Laboratory Quality Management System handbook (access checked 2026-07-20).
Bench-use checklist
- Verify product identity, catalogue number, lot, expiry, and storage history.
- Document preparation and incubation exactly as controlled in the SOP.
- Define controls and acceptance criteria before testing.
- Record raw observations, control response, reading time, and confirmation decision.
- Escalate failed controls, atypical reactions, and departures through the quality system.