The analytical question addressed by BRYANT AND BURKEY Medium Culture Media is straightforward to state but easy to compromise: can the intended organism or reaction be observed consistently under controlled conditions? The discussion below connects its documented role with preparation variables, controls, interpretation, and the limits of inference. Catalogue 610142 is discussed as a laboratory measurement component; implementation should follow the laboratory SOP and validated reference method.
Analytical scope and method role
BRYANT AND BURKEY MEDIUM is a medium or the enumeration of lactate- fermenting spore-forming anaerobes in milk and dairy products.
Method principle
Tryptone, meat extract and L-cysteine provide nutrients and cofactors required for good growth of clostridia. Yeast extract supplies B-complex vitamins which stimulate bacterial growth. Selectivity of this medium is achieved through the addition of sodium acetate which is also the principal promoter of spores germination.
Formula and functional interpretation
(g/L) Tryptone 15.0 Yeast Extract 5.0 Meat Extract 7.5 Sodium Acetate 5.0 L- Cysteine 0.5 Resazurin 0.002 Calcium Lactate 5.0 Final pH =5.9 ± 0.2 at 25°C
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
Preparation: Suspend 38.0 g of powder in 1 litre of distilled or deionized water. Heat until completely dissolved. Dispense 10 mL amounts into tubes. Sterilize in the autoclave at 121 °C for 15 minutes.
Procedure: 1. Prepare tenfold dilutions of the sample and inoculate triplicate tubes of BRYANT AND BURKEY MEDIUM with 1 mL of each sample dilution. 2. Pour approximatively 2 mL of melted paraffin (60-65°C), previously autoclaved at 121°C for 20 minutes, into each tube. 3. Heat the tubes to 75°C to kill vegetative cells and activate spores; allow to cool to room temperature. 4. Incubate tubes at 35°C for 6 days. 5. Examine tubes for growth and gas production after 48 hours incubation and daily for up to 6 days.
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
Tubes showing both growth and gas production (indicated by upward movement of the paraffin more than 1 cm) are considered positive for the presence of lactate -fermenting clostridial spores. Determine the spore count using the Most Probable Number (MPN) method.
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.
Storage, stability, and pre-use inspection
The powder is very hygroscopic: store the powder at 10-30 °C, in a dry environment, in its original container tightly closed and use it before the expiry date on the label or until signs of deterioration or contamination are evident. Store prepared media at 2-8°C. WARNING and
Receipt and storage records should reconstruct temperature exposure, lot rotation, expiry, container integrity, and time outside controlled storage. Inspect colour, clarity, fill volume, gel integrity, contamination, dehydration, and precipitate before use.
Limitations and boundaries of use
The product is not classified as hazardous by current legislation and does not contain harmful substances in concentrations of ≥1%. It is nevertheless recommended that the Safety Data Sheet be consulted on its correct use. The product must be used only by properly trained operators.
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 610142.
- 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.