Efficient inactivation of B urkholderia pseudomallei or F rancisella tularensis in infected cells for safe removal from biosafety level 3 containment laboratories

Working with infectious agents that require BSL ‐3 level containment agents offers many challenges for researchers. BSL ‐3 containment laboratories are usually not equipped with expensive specialty equipment that is needed for studies such as flow cytometric analysis, microscopy, and proteomic analyses. Therefore, for most researchers that are working with BSL ‐3 level infectious agents, removal of samples from BSL ‐3 laboratories for these types of studies is necessary, and methods for complete and dependable inactivation of the samples are required. In this report, we have carried out a thorough characterization of the effectiveness of paraformaldehyde fixation for inactivation of cell samples infected with the intracellular bacterial agents Burkholderia pseudomallei ( Bp ) and Francisella tularensis ( Ft ), both of which are Tier 1 select agent pathogens that require BSL ‐3 containment. We have demonstrated that cells infected with these pathogens are completely inactivated via 5‐min treatment with 4% paraformaldehyde. Moreover, a 15‐min treatment with 2% paraformaldehyde completely sterilized both Bp ‐ and Ft ‐infected cells. These studies also revealed that Bp is significantly more sensitive to paraformaldehyde treatment than Ft . Our findings have clearly demonstrated that a 15‐min treatment of Bp ‐ or Ft ‐infected cells with 4% paraformaldehyde solution will allow for safe removal of the cell samples from BSL ‐3 laboratories for downstream studies.