Prevention

Respirators are not normally required for work in a TB laboratory. However, they may be recommended after a risk assessment if cultures are being manipulated within a TB-containment laboratory. Even if not worn regularly, respirators must be available in laboratories where culture manipulations are performed in case an accidental biohazard (such as a spill) occurs outside the BSC. Respirators should be included as part of a laboratory’s spill clean-up kit.

Respirators should never be used as a substitute for a properly maintained and functioning BSC.

Laboratory gowns should have long sleeves and open in the back. When the laboratory technician is standing, the gown must extend below the height of the workbench; the gown should fully cover the technician’s lap when he or she is sitting. Reusable gowns should be autoclaved before being washed. Gowns must not be taken home for washing; laundering services should be provided at or near the facility. Laboratory gowns should be changed at least once a week and immediately after being overtly contaminated.

During the centrifugation process, aerosols may be produced. Consequently, safety measures must be strictly followed when operating the centrifuge.

The two types of BSCs described below are best suited for use in moderate-risk laboratories and in high-risk laboratories (TB-containment laboratories).

Class I

• This type of BSC provides personal and environmental protection but does not offer product protection. This lack of product protection may contribute to increased contamination rates, especially when preparing and inoculating liquid cultures (see Figure 1).

Class II

Owing to their small size, droplet nuclei aerosols may be generated by certain laboratory procedures without the laboratory worker’s knowledge; this may result in the inhalation of infectious agents or cross-contamination of work surfaces or materials. BSCs are designed to protect people and the environment from infectious agents and, depending on their classification, offer varying degrees of protection from contamination of specimens and cultures.

Safety equipment may be used to eliminate or reduce certain risks in TB laboratories (Table 4). Such equipment offers no assurance of protection unless the operator is competent and uses proper techniques. Equipment should also be tested regularly to ensure that it continues to perform safely.

Similar to the moderate-risk laboratory, there are two levels of containment in a high-risk laboratory: the BSC (primary containment) and the laboratory itself (secondary containment).

In addition to the hazards described in Chapter 4 for TB laboratories classified as moderate risk, and the general risks that are addressed by the biosafety measures described in Chapter 2, laboratories classified as high-risk (or containment) also face the following challenges, all of which increase risks:

The term TB-containment laboratory refers to a facility that has the minimum design features necessary to safely manipulate TB cultures. This type of facility may or may not meet all of the requirements of a Biosafety Level 3 laboratory as described in WHO’s Laboratory biosafety manual.² All laboratory facilities must comply with local and national regulations.

In addition to the general risks that are addressed by the biosafety measures described in Chapter 2 (such as unauthorized persons in the laboratory, mouth pipetting, cluttered work stations, improper waste disposal), the TB laboratory classified as moderate risk also faces the following challenges, all of which increase risks: