contamination control

Question 1: What is contamination control?

“Contamination control is the process of preventing, detecting and minimising unwanted microorganisms, particles or other contaminants from affecting samples, products, equipment or the laboratory environment. In pharmaceutical QC, it is essential for maintaining product quality, protecting sample integrity and ensuring reliable results.”

Question 2: What are the main sources of microbial contamination in a laboratory?

“Common sources include personnel, hands and clothing, airborne particles, contaminated equipment or surfaces, non-sterile materials, water, and poor sample-handling practices. Contamination can also occur through incorrect storage or inadequate cleaning.”

Question 3: How would you prevent contamination when handling microbiological samples?

“I would follow the approved SOP, perform appropriate hand hygiene, wear the required PPE, disinfect the work area, use sterile equipment where required, minimise the time samples are open and avoid touching sterile surfaces. I would also label and handle samples correctly and dispose of waste appropriately.”

Question 4: Why is contamination control important in pharmaceutical manufacturing?

“Contamination could compromise product quality and, depending on the product, pose a risk to patient safety. Effective contamination control helps maintain clean manufacturing conditions, prevents cross-contamination and supports compliance with GMP requirements.”

Question 5: What is cross-contamination?

“Cross-contamination is the unintended transfer of microorganisms or other contaminants from one sample, product, surface or environment to another. It can be prevented through appropriate segregation, cleaning, correct handling, dedicated equipment where required and good aseptic technique.”

Question 6: You discover microbial growth in a negative control. What would you do?

“I would recognise that the negative control may indicate contamination or another issue affecting the test's validity. I would check the test records and controls, inform my supervisor, document the finding and follow the relevant SOP and investigation procedure. I would not report the test as valid until the issue had been assessed.”

Question 7: You accidentally drop a sterile item onto the laboratory bench. What do you do?

“I would treat the item as potentially contaminated and replace it with a new sterile item. I would assess whether the sample or procedure had been affected and follow the relevant SOP. I would never assume the item was still sterile because it looked clean.”

Question 8: What would you do if you noticed an environmental monitoring result above the action limit?

“I would promptly notify my supervisor, verify the sample identification and recorded result, and follow the established investigation procedure. The investigation may consider the organism identified, location, recent activities, cleaning records and previous monitoring trends. Any required corrective actions would be documented, and I would not independently dismiss or invalidate the result.”

Question 9: What would you do if you noticed a colleague using poor aseptic technique?

“I would respectfully raise the concern and act promptly to prevent potential contamination. If a sample or test might have been affected, I would inform the appropriate supervisor and ensure the incident was managed according to the laboratory's procedures.”

Question 10: What if you suspect that your sample has been contaminated but you are unsure?

“I would not make assumptions or ignore the possibility. I would stop and assess the situation, preserve the relevant records, inform my supervisor and follow the SOP to determine whether the sample or result was affected. Any repeat testing would need to be justified and authorised under the applicable procedure.”

Question 11: What is environmental monitoring?

Environmental monitoring assesses the cleanliness and microbiological condition of controlled environments. Depending on the monitoring programme, it may involve air sampling, settle plates, surface contact plates or swabs, and personnel monitoring.

Question 12: What is the difference between active air sampling and passive air monitoring?

Active air sampling uses equipment to draw a measured volume of air across a collection medium. Passive monitoring commonly uses settle plates to detect microorganisms that settle from the air onto the agar surface over a specified exposure period.

Question 13: Why are settle plates used in cleanrooms?

“They help monitor viable microorganisms that settle from the air onto a surface over time. They provide information about potential microbial contamination, but they do not measure a precise volume of air.”

Question 14: Why is gowning important in a cleanroom?

“Personnel can shed skin cells, hair and microorganisms. Correct gowning helps reduce the introduction of contamination into controlled areas. The gowning procedure and clothing requirements depend on the cleanroom classification and site SOP.”

Question 15: What is the difference between an alert limit and an action limit?

“An alert limit indicates a result that may be unusual and warrants attention or increased monitoring according to the procedure. An action limit indicates a more significant excursion that requires investigation and appropriate action. The exact response depends on the site's approved procedures.”

What is the difference between cleaning and disinfection?

Cleaning removes soil and residues; disinfection inactivates susceptible microorganisms.

Does disinfection always kill bacterial spores?

No. Effectiveness against spores depends on the disinfectant and its validated use.

Why must you follow the disinfectant contact time?

The surface must remain exposed for the specified time to achieve the intended effectiveness.

Why may a laboratory rotate disinfectants?

A site may use different agents to address different microorganisms or risks, according to its validated contamination control programme. Rotation is not automatically required everywhere.

What is sterilisation?

A validated process intended to eliminate all viable microorganisms, including spores.

Why is cleaning validation important?

It provides documented evidence that a cleaning process consistently meets predefined acceptance criteria