Phase 1
Isolate Recovery and Preservation
1Recover the isolate using aseptic technique
Colony picked from the original growth media using validated aseptic technique to avoid introducing cross-contamination during recovery.
USP <1113>
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2Sub-culture and purify the isolate
Isolate sub-cultured to confirm purity as a single organism before proceeding to identification, since a mixed culture will produce an unreliable result.
USP <1113>
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3Preserve the isolate for future reference
Purified isolate preserved using a validated storage method, such as cryopreservation, and added to the site's reference culture library with full traceability.
PDA TR 33
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4Determine required identification level
Required identification depth determined based on the recovery source, its GMP grade, and whether the isolate's morphology suggests an organism of particular concern.
EU GMP Annex 1 2022
Phase 2
Method Selection and Testing
5Select the identification method
Phenotypic, MALDI-TOF, or genotypic method selected based on the required identification level and the organism's apparent characteristics.
USP <1113>
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6Perform Gram stain and morphology assessment
Initial characterization performed regardless of the confirmatory method selected, providing a baseline description and a plausibility check for the final result.
USP <1113>
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7Perform confirmatory identification testing
Selected method executed per its validated procedure, generating a genus or species-level identification result against the reference database.
PDA TR 33
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Does the confirmatory result align with the initial phenotypic characterization?
YES → Accept identification
NO → Reconcile with alternate method
Phase 3
Result Interpretation and Risk Assessment
8Compare against the objectionable organism list
Identified organism checked against the site's list of objectionable and indicator organisms, which is informed by product route, patient population, and process characteristics.
USP <1111> · EU GMP Annex 1 2022
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9Assess source-appropriateness
Consider whether the identified organism is plausible for its recovery source and location, since an unexpected organism type can itself be a signal worth investigating.
PDA TR 33
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10Escalate high-risk identifications
Spore-forming organisms in Grade A/B areas, gram-negative organisms in water systems, or any objectionable organism finding escalated immediately for investigation.
EU GMP Annex 1 2022
Phase 4
Library Integration and Trending
11Add isolate data to the identification library
Identification result, recovery source, date, and preserved isolate reference added to the site's microbial identification database for future comparison.
PDA TR 33
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12Update trending by organism, location, and time
Identification data trended alongside quantitative monitoring results, surfacing recurring organisms at specific locations that a colony count alone would not reveal.
ICH Q10
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13Periodic library review
Identification library reviewed periodically to identify recurring organisms, new organism types, or shifts in the site's microbial flora over time.
EU GMP Annex 1 2022
Identification Method Comparison
Phenotypic (Biochemical)
Lower cost and widely available, but limited discriminatory power for atypical or closely related organisms, and typically resolves only to genus level.
Best for routine, low-risk isolates
MALDI-TOF Mass Spectrometry
Fast and increasingly standard for routine identification, but accuracy depends entirely on the organism being well represented in the reference database.
Best for routine to moderate-risk isolates
Genotypic (Sequencing)
Highest discriminatory power and considered the gold standard for objectionable or atypical organisms, at the cost of longer turnaround and higher expense.
Best for high-risk and objectionable isolates
High-Risk Organism Escalation Steps
Step 1 - Confirm via a second orthogonal method
High-consequence identifications confirmed using a second, independent method before the finding drives major investigation decisions.
Step 2 - Cross-reference against the CCS critical organism list
Check the identified organism against the site's Contamination Control Strategy list of organisms of particular concern for the affected area.
Step 3 - Assess route into product
Evaluate how the organism could plausibly have reached the recovery location, considering personnel, materials, and environmental pathways.
Step 4 - Notify QA and the investigation team immediately
High-risk identifications communicated without delay so the broader investigation can incorporate the identification promptly.
Step 5 - Feed the finding into CCS and trend review
Result incorporated into both the CCS risk picture and the ongoing organism trending dataset, not treated as a one-time isolated event.
Isolate Preservation Requirements
Validated preservation method
Isolates preserved using a validated method, such as cryopreservation at ultra-low temperature, confirmed to maintain organism viability over the defined retention period.
Defined retention period
Reference isolates retained for a documented period sufficient to support future comparison and trending, per site procedure.
Full chain of custody
Traceability maintained from original recovery through sub-culturing, identification, and final storage location.
Reference culture traceability
Positive control and method suitability challenge organisms sourced from a recognized culture collection with documented passage history.