Define testing points in advance
- On receipt or during quarantine of incoming cultures.
- Before release into shared routine work.
- Before creating or releasing a cell bank.
- Before critical experiments or transfer to another laboratory when required.
- After an unexplained culture change or contamination incident.
- At a routine interval appropriate to laboratory risk and quality requirements.
Choose a method whose limitations match the decision
Nucleic-acid amplification can provide sensitive and rapid screening but remains vulnerable to sampling, inhibition and contamination controls. DNA staining provides visual evidence but may be less sensitive and interpretation can be difficult. Culture-based or independent services can provide additional confirmation.
Use positive, negative and process controls appropriate to the method. A result without valid controls should not be treated as a definitive release decision.
Sampling conditions matter
Follow the assay instructions for culture state, time since medium change, sample type and storage. Sampling immediately after antibiotic exposure or under conditions that reduce organism load can contribute to misleading results.
Record the culture identifier, sample time, passage information, method, kit or service, controls and result interpretation.
Respond to a positive or unresolved result as a containment event
Isolate the culture, identify shared pathways and follow the laboratory response procedure. For replaceable cultures, recovery from a verified clean bank is generally easier to defend than an undocumented treatment attempt.
When treatment is considered for irreplaceable material, define independent confirmation, post-treatment observation and identity checks before the culture returns to routine work.