Most laboratories handling clinical specimens of suspected tuberculosis will not know if an extensively drug-resistant tuberculosis (XDR TB) strain is present until after testing is completed on the materials. Initially, BSL-2 practices and procedures, containment equipment, and facilities are required for non-aerosol-producing manipulations of clinical specimens such as preparation of acid-fast smears. All aerosol-generating activities must be conducted in a biological safety cabinet (BSC). Use of a slide-warming tray, rather than a flame, is recommended for fixation of slides. Liquefaction and concentration of sputa for acid-fast staining may be conducted safely on the open bench by first treating the specimen in a BSC with an equal volume of 5% sodium hypochlorite solution (undiluted household bleach) and waiting 15 minutes before processing.
If samples are being received from a known or highly suspected source of XDR TB, BSL-2 with full BSL-3 practices are highly recommended for manipulations of the clinical specimens, including additional personal protective equipment (PPE) and autoclaving of waste before leaving the laboratory (see 5th edition BMBL for full description of BSL-3 practices).4
4. Centers for Disease Control and Prevention. "Interim Laboratory Biosafety Guidance for Extensively Drug-Resistant (XDR) Mycobacterium Tuberculosis strains." CDC.gov, Accessed December 15, 2021, https://www.cdc.gov/tb/topic/laboratory/biosafetyguidance_xdrtb.htm
