The joys of biological containment

The foot and mouth disease outbreak near Pirbright in the UK and the associated issues of biological containment  have brought back for me the time I spent working in a (different) biological containment lab >10 years ago. What did we do to contain the organism?

The lab was designated category 3+ (United Kingdom Advisory Committee for Genetic Manipulation.). Probably not as high containment as the labs at Pirbright because what we were working on was not such an economically important or infectious disease and the organisms being contained was an E. coli with a fragment of a pathogenic factor in it for study. The aim was to prevent this genetically modified bacterium escaping and establishing in the environment.

The containment strategy was multi pronged.

First, the E. coli we worked with (E. coli K12) was designed to be crippled to the point of only being able to survive in especially enriched culture media rather than the environment. This was (and still is) a standard precaution for micro-organisms created by genetic modification.

Then there was the physical containment of the organism. It was kept and grown in sealed containers that were only opened inside a class 2 biological safety cabinet. These are basically boxes with a fan and a filter for the exiting air that removed any infectious agents. There is a small gap at the bottom through which one works and there is a strong flow of air into this gap. This airflow prevented aerosols of bacteria escaping the box through the gap. Theoretically no bacteria could get out into the laboratory around the safety cabinet if it was correctly used. But just in case, the lab was inside a building that was kept at ‘negative pressure’. Air flow in the building was directed so that air only left the building via filters that removed bacteria. This prevents airborne pollution with bacteria.

Next there are the staff working on the organisms, they need to be safe and uncontaminated. The access to the locked building was restricted to named individuals who were trained in the safety procedures. All the usual general microbiology lab rules no eating, drinking applied. On top of that we wore lab coats of a design that didn’t button at the front and wore protective gloves in the lab and more gloves when working in the safety cabinet., which were discarded in the cabinet. The remaining gloves were taken off, hands washed and shoes changed or decontaminated in a disinfectant footbath on exiting the lab. To exit the building we had to take off all clothing worn in the lab, leave it in a changing room (on the inside), shower for a minimum time, with soap and shampoo and then get dressed again in our own clothes in a changing room on ‘the outside’. No jewellery at all was allowed inside. Never been so clean as when I worked in that lab having several showers a day!

Waste disposal was also key. Any waste or documents, or clothing exiting the lab had to be treated in an autoclave at specified temperature and pressure. Documents could be fumigated with formaldehyde before leaving the building and then all the waste was incinerated. We were so pleased when we got a computer in there and could transfer documents electronically! The general waste water was treated in a special treatment plant.

What a lot of procedures! However as Robert said, in his blog, for successful containment staff must follow all of them to the letter. It is costly and time consuming to implement these procedures. All the equipment and filters have to be regularly checked to ensure no loss of the integrity of the barriers to organism release. Time or financial pressure could make people cut corners. Then there are the emergencies – fire, for example or a power failure, or tripping up and breaking the sealed container of bacteria while walking across the lab. There were set procedures for dealing with accidents and spillages, but there can still be unforseen events.

It seems there was no emergency at Merial or Pirbright to account for the possible release of virus, and unless procedures have recently changed and a flaw introduced, the procedures are probably all OK. The accidental release of the foot and mouth disease virus has to be down to human error or a deliberate act.

How often do releases of organisms into the environment from containment facilities occur? "In recent history, in Europe there have been over 10 different accidental animal infections with FMD virus due to human error" says the World Organisation for Animal Health to Channel4 news. A bit coy. Web reports suggest Pirbright has been involved in 2 previous lapses of containment for foot and mouth disease, in 1960 and 1970. See The Guardian and Channel 4 news.

Microbiology laboratory workers are often the first to suffer from infections at work caused by failure of containment. Try searching laboratory workers’ and vv2*‘ on Global Health.

This book covers the subject in detail: Biological safety: principles and practices. Fleming, D. O. , Hunt, D. L. / Biological safety: principles and practices, 2006, No. Ed.4, pp. xviii + 622 pp. , many ref.

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