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Guidance on laboratory work with hazard group 3 enteric pathogens

Those intending to work with certain Hazard Group (HG) 3 agents may not necessarily need to use all the containment measures normally required at Containment Level (CL) 3 because of the nature of the agent and/or the nature of the work that is being carried out. The agents to which this applies are shown in Annex 1 to the Approved List of Biological Agents.

This temporary document provides guidance on working with HG3 enteric bacteria. It was originally Appendix 24 of the Supplement to the Categorisation of biological agents and categories of containment guidance.

Until recently, the Advisory Committee on Dangerous Pathogens (ACDP) guidance 'Categorisation of biological agents and categories of containment' contained the 4th edition of the Approved List of biological agents. The Approved List has now been published by HSE as a stand-alone publication entitled The Approved List of Biological Agents [500kb] .

The ACDP will be publishing new guidance (Biological agents: managing the risks) for laboratory workers and healthcare workers who could be exposed to biological agents on a frequent basis. The following guidance will appear in an updated form in this new guidance.


Introduction

1. The following guidance applies to laboratory work with the enteric bacteria that are categorised as HG 3 in accordance with Schedule 3 of the Control of Substances Hazardous to Health Regulations 2002 (COSHH). It should also be read in conjunction with the latest edition of the Approved List of Biological Agents (2004).

Scope

2. The HG 3 enteric bacteria covered by this guidance are:

3. The above agents have all been known to cause severe disease and have all caused a number of laboratories acquired infections. All these organisms are known to have a low infective dose, particularly Shigella dysenteriae and verocytotoxigenic E. coli (VTEC), where the infective dose is thought to be less than 100 viable organisms1. In recognition of the fact that these agents do not primarily infect via the airborne route, some of the CL 3 measures may be dispensed with subject to a local risk assessment indicating it is safe to do so.

4. The guidance follows the normal structure and hierarchy of controls required by COSHH, namely:

Substitution with a safer biological agent

5. The risks associated with S. dysenteriae and VTEC are predominantly associated with the production of toxins. Regulation 7(1) of COSHH requires that exposure to a biological agent is avoided if possible or that a safer biological agent is used. Therefore, where work is being carried out for quality assurance or quality control purposes, or certain types of research, the possibility of using non-toxigenic or less pathogenic strains must be considered, unless the work requires the production of the toxin. Such strains are readily available from national culture collections and those using them must ensure that the organism is handled under the containment conditions appropriate to the Hazard Group (eg most non-toxigenic E. coli are in HG2).

Diagnostic work

6. When there is uncertainty about the presence of HG3 enteric bacteria or any other infectious agents, eg in clinical specimens such as stools and blood culture samples, routine diagnostic work can usually be undertaken under normal CL 2 conditions.

7. However, if there is a strong indication or likelihood that HG3 organisms might be present then derogated CL3 measures (see below) must be used. Examples of where this may be necessary include:

8. In food laboratories, an assessment of the laboratory conditions required should take into account the likelihood and frequency of isolation of HG 3 organisms. Under normal circumstances isolation of these organisms is likely to be rare. Therefore, CL 2 would normally be sufficient unless there are strong grounds for suspecting that HG 3 enteric bacteria may be present in a particular sample or where there is presumptive identification of them, in which case all further work must be carried out at CL 3.

9. In all cases, a local risk assessment must consider the possible risks associated with the work being undertaken. In particular, close attention should be paid to procedures which may present a risk of aerosol or contaminating droplet formation and/or which may concentrate any HG 3 organism present in a stool or food sample. Examples of techniques, which may produce aerosols or contaminating droplets, are immunomagnetic separation and inoculation of plastic test kits. There is a requirement even at CL 2 to conduct any activity that may produce an infectious aerosol in a microbiological safety cabinet.

CL 3 measures for HG3 enteric bacteria

10. Any work involving the intentional culture or manipulation of known HG 3 enteric bacteria must use full CL 3 laboratory containment measures. The control measures for laboratories and animal rooms can be found in Part II of Schedule 3 of COSHH. Further guidance on the detailed measures for CL 3 laboratories can be found in the ACDP categorisation publication and the Health Services Advisory Committee publications Safe working and the prevention of infection in clinical laboratories2.


Derogation from CL3

11. Derogated CL 3 may be used for certain diagnostic work, as indicated in paragraph 7. All of the CL 3 measures must be applied, except the measures highlighted as items 3, 4 and 10 in Table 1 may be reduced. Any decision to reduce containment measure should be made on the basis of a local risk assessment, which takes account of the nature of the work, the volume of culture and the procedures and equipment to be used for, propagating, concentrating or analysing the organism. Particular issues to address are the potential for dispersal of the agent or contamination of staff, equipment or surfaces.

12. The local assessment may mean that full CL 3 conditions are necessary to protect staff in the laboratory and others outside who may beat risk. The laboratory may also need to be designed and operated for work with other HG 3 agents not subject to derogation.

Information, instruction and training

13. All staff who work with or who may be exposed to HG 3 biological agents must have a clear understanding of the risks associated with the agents and the actions to be taken to safeguard their health. These should be set out in local codes of practice, which should be made available to individuals, including newcomers and temporary staff.

14. Staff who work in CL 3 laboratories should be properly trained in the procedures and requirements. A video giving practical advice on this has been prepared by HSE, in addition to ACDP guidance.3, 4

Immunisation and health surveillance

15. COSHH Schedule 3 requires that where an effective vaccine is available, and health surveillance, and the local assessment indicates that there is a risk to staff, then it should be made available to staff free of charge.

16. COSHH requires that health surveillance must be provided where appropriate for the protection of the health of employees. In most cases, for work with HG 3 enteric bacteria it should be sufficient to set up and maintain a health record as defined in COSHH.5 Staff should be advised of the signs and symptoms of infection with HG 3 enteric bacteria and told to report any illness that may be linked to exposure at work to their GP or occupational health service.

17. COSHH requires that a list of workers exposed to HG 3 agents (including those subject to derogation) be kept for at least 40 years after the last known exposure. This should indicate the type of work done, the agents handled and any known exposures, accidents or incidents. It may be possible to combine this with any health record under COSHH.

18. An official local record should be made of all accidents and occurrences with infectious or potentially infectious material involving the exposure of individuals. In some cases the HSE must be notified under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1995. Employers must report any infection reliably attributable to work with live or dead humans or animals, exposure to blood or body fluids or any potentially infected material derived from any of the above. There is also the need to report any accident or incident, which resulted or could have resulted in the release or escape of HG 3 enteric bacteria (or other HG 3 or 4 biological agents). Further information can be obtained from the Health and Safety Executive

Table 1: Derogated laboratory Containment Level 3 (for certain diagnostic procedures - paragraph 11)

  1. The laboratory must be separated from other activities in the same building
  2. Access to the laboratory is to be restricted to authorized persons
  3. The laboratory does not need to be maintained at an air pressure negative to atmosphere unless it is mechanically ventilated. In practice negative pressure may in any case be achieved because of the use of a microbiological safety cabinet extracting to outside via a HEPA filter
  4. The laboratory need not be sealable to permit disinfection.(This derogation will not normally apply in cases where the laboratory needs to be disinfected by fumigation if, for example, a spillage has occurred or maintenance work is needed.)
  5. There must be specified disinfection procedures
  6. Bench surfaces and the floor must be impervious to water, easy to clean and resistant to acids, alkalis, solvents and disinfectants
  7. There must be safe storage of biological agents
  8. There must be an observation window or an alternative so that occupants can be seen
  9. The laboratory must contain its own equipment, so far as is reasonably practicable
  10. A microbiological safety cabinet is not essential. (But any laboratory procedures that may give rise to contaminating aerosols or droplets should be suitably contained, for example in a microbiological safety cabinet, isolator or other suitable containment.)
  11. An incinerator must be accessible for the disposal of animal carcasses

References

1 Willshaw G A et al Verocytoxin-producing Escherichia coli in beefburgers linked to an outbreak of diarrhoea, haemorrhagic colitis and haemolytic uraemic syndrome in Britain Letters in Applied Microbiology 19, 304-307

2 Health Services Advisory Committee Safe working and the prevention of infection in clinical laboratories and similar facilities HSE Books 2003 ISBN 0 7176 2513 3

3 Working safely at Containment Level 3 (Video) HSE Books

4 Advisory Committee on Dangerous Pathogens The management, design and operation of microbiological containment laboratories HSE Books 2001 ISBN 0 71762034 4

5 Health and Safety Commission Control of Substances Hazardous to Health Regulations 2002 Approved Code of Practice and Guidance L5 HSE Books 2002 ISBN 0 7176 2534 6