Bioburden and Microbial Limits Testing Procedure

Standard operating procedure for monitoring bioburden and microbial limits in intermediates and bulk materials prior to sterile filtration.

Steps

• Verify the sample request and acceptance criteria
  The microbiology analyst verifies that the sample request matches the batch record or sampling plan. The analyst confirms the material is an intermediate or bulk intended for pre-filtration monitoring, the required test method, the sample quantity, and the acceptance criteria. The analyst escalates any mismatch as a deviation before proceeding.
• Inspect the sample container and chain of custody
  The microbiology analyst inspects the sample container for integrity, correct labeling, and evidence of leakage, damage, or contamination. The analyst verifies chain-of-custody documentation and confirms the sample has remained within the defined hold time and temperature limits. The analyst rejects and escalates any compromised sample.
• Prepare the test area and required materials
  The microbiology analyst prepares the test area according to the validated method and local contamination control requirements. The analyst gathers sterile diluent, filtration components, media, pipettes, labels, and worksheets. The analyst verifies that incubators, balances, and other critical equipment are within calibration or qualification status.
• Perform the sample preparation and dilution
  The microbiology analyst mixes the sample as required by the method and prepares any necessary serial dilutions using sterile technique. The analyst records the dilution scheme, sample volume, and any observations such as visible turbidity, particulates, or unusual odor. The analyst discards and documents any preparation that is contaminated or outside method tolerance.
• Filter or plate the sample using the validated method
  The microbiology analyst performs membrane filtration, plating, or another validated enumeration method specified for the product and sample matrix. The analyst maintains aseptic technique throughout transfer and ensures the full test volume is processed when required. The analyst records any filtration difficulty, clogging, or incomplete transfer as a deviation.
• Incubate the test units under validated conditions
  The microbiology analyst places the test units into the validated incubator or incubation system. The analyst verifies the incubation temperature, duration, and any staged incubation requirements specified by the method. The analyst documents the start time and confirms the units are clearly identified to prevent mix-ups.
• Review incubation completion and count the colonies
  The microbiology analyst removes the test units after the validated incubation period and reviews each unit for growth. The analyst counts colonies using the approved method and records the result in the worksheet or LIMS. The analyst notes any spreaders, merged colonies, or atypical growth and applies the method-defined counting rules.
• Compare results to the acceptance criteria
  The quality reviewer or microbiology analyst compares the final result to the predefined acceptance criteria for the intermediate or bulk material. The reviewer confirms whether the result is within tolerance or represents a deviation. The reviewer documents the disposition path based on the outcome.
• Initiate deviation and escalation for an out-of-limit result
  The quality reviewer places the lot or sample status on hold and initiates a non-conformance or deviation record. The reviewer notifies the manufacturing supervisor, quality assurance, and microbiology leadership per the escalation matrix. The reviewer preserves all raw data, test units, and related records for investigation.
• Document the final result and archive the record
  The microbiology analyst documents the final result, method used, analyst identity, date, and any deviations or observations in the controlled record system. The analyst ensures the record is complete, legible, and attributable in accordance with documented information requirements. The analyst forwards the record for QA review and archives all supporting data per retention requirements.