Prevention

The recommendations in this chapter are the minimum requirements needed to limit or reduce risks of infection in laboratories carrying out specific procedures that are considered to have a moderate risk of spreading TB. Additional measures may be deemed necessary following a site-specific risk assessment.

In addition to the general risks that are addressed by the biosafety measures described in Chapter 2, the low-risk TB laboratory may also face the following challenges, all of which increase risks:

• bench spaces may be used improperly;
• specimen containers may leak;
• specimens manipulated carelessly may lead to subsequent aerosolization;
• specimens may be shaken vigorously;
• ventilation or illumination may be poor. 

The recommendations in this chapter are the minimum requirements needed to limit or reduce risks of infection in laboratories carrying out specific procedures that are considered to have a low risk of spreading TB. Additional measures may be deemed necessary following a site-specific risk assessment.

All positive TB cultures must be autoclaved before disposal. An autoclave should be available close to or in the laboratory where TB culture is performed.

All contaminated (that is, potentially infectious) materials except sharps should be placed in disposable plastic bags before being transported for incineration. If possible, materials from TB laboratories should not be discarded in a landfill even after decontamination.

Broken slides and used slides must be disposed of in a sharps container. Containers for sharps disposal must be puncture-proof, have a fitted lid, and must not be filled to capacity. When they are three quarters full, they should be placed in containers for infectious waste and incinerated. Containers for sharps disposal must not be discarded in a landfill unless they have been incinerated or autoclaved. Used slides must not be reused.

A system for identifying and separating infectious materials and their containers should be adopted. Categories may include:

• uncontaminated (non-infectious) waste that can be reused, recycled or disposed of in the same way as general household waste;
• contaminated (infectious) sharps, such as broken glass, syringes and slides;
• contaminated infectious material to be disposed of by burying, incinerating or autoclaving.

The killing action of disinfectants depends on the population of organisms to be killed, the concentration used, the duration of contact, and the presence of organic debris.

Proprietary disinfectants recommended as suitable for use in TB laboratories are those containing phenols, chlorine or alcohol. These are usually selected depending on the material to be disinfected.

Phenol

Separate autoclaves should be used to sterilize solutions or glassware (clean materials), and to decontaminate infectious materials.

The following materials are suitable for autoclaving:

To incinerate hazardous waste properly requires an efficient means of controlling the temperature, and a secondary burning chamber. Many incinerators, especially those with a single combustion chamber, are unsatisfactory for dealing with infectious materials or plastics. If this type is used, such materials may not be completely destroyed, and the effluent from the chimney may pollute the atmosphere with microorganisms, toxic chemicals and smoke. However, there are many satisfactory configurations for combustion chambers.

Waste-management procedures must comply with all pertinent local or national requirements and regulations. Waste is anything that is to be discarded. The overriding principle in minimizing risks from waste is that all infectious materials should be decontaminated, incinerated, prepared to be buried or autoclaved. Discard bags should be used to segregate waste. Most glassware, instruments and laboratory clothing will be reused or recycled.

The principal questions to be asked before any objects or materials are removed from a laboratory are: