Biological safety cabinet: ultraviolet radiation effect on mycobacteria

Biological safety cabinet (BSC) is the major equipment which is the primary means of containment of infectious microorganisms aerosols generated from laboratory procedures, and the decontamination using ultraviolet radiation -, constitute a stage of Good Laboratory Practices. The objective of this study was to evaluate the effect of UV lamp of class II B2 cabinet on varied mycobacteria species and to correlate them with UV exposition time. Reference strains were subcultivated and incubated at 37 degree C until getting a turbidity equivalent to that of MacFarland 1 standard. From this bacterial suspension, 100 mu L were plated into 7H11 medium; the plates were partially covered with aluminium paper and exposed to UV radiation for 5 and 10 minutes. After UV exposition, the paper was removed and the plates were incubated at 37 degree C for 30 days. All plates showed no bacterial growth at the side exposed to the UV radiation, while a regular and abundant bacteria growth was observed at the other half part that was covered with paper. Switching on the UV lamp for 15 minutes after using the cabinet and for 15 minutes before starting any activity inside the cabinet guarantees proper decontamination. This biosafety practice is recommended to decontaminate the BSC and also materials that need to be withdrawn from the cabinet.