Contain first
- Stop routine movement of the suspect culture through shared incubators, microscopes and biosafety-cabinet workflows when feasible.
- Label the culture and associated waste clearly and notify the responsible laboratory lead.
- Identify cultures, reagents and equipment that may share a timeline or handling pathway.
- Follow institutional biosafety and decontamination procedures rather than improvising treatment.
Describe observations without overcalling the organism
Record medium clarity and color, visible particles, motion, filament-like structures, surface films, odor only when safely observed, attachment changes, growth rate and the distribution of the finding across vessels.
Cell debris, precipitated supplements, detached cells, bubbles and optical artifacts may resemble contamination. Conversely, mycoplasma may produce no obvious turbidity.
Use an appropriate confirmation method
Select testing based on the suspected event, institutional requirements and the consequence of a false result. Molecular assays, DNA staining, culture-based methods and independent testing services have different strengths and limitations.
For a critical culture, confirmation and identity review may be more defensible than attempting to infer the cause from a microscope image alone.
Prefer recovery from a verified bank over routine antimicrobial rescue
Discarding the affected culture and recovering from a documented clean bank is often the clearest route to restoring traceability. Antimicrobial treatment can mask contamination, select resistant organisms, alter cell behavior and prolong uncertainty.
After an event, review the process path: quarantine practice, reagent sharing, cabinet workflow, incubator cleaning, water-pan handling, pipette use and the timing of routine testing.