Bt species are believed to be non-infectious and have only on rare occasions been associated with opportunistic infections in humans. Nevertheless, the close relationship Sirolimus solubility dmso between Bt and the human pathogen Bacillus cereus continues to be substantiated and gives rise to new questions [26–29]. The present study showed that instilled or even inhaled Bt spores may be present in the lung and extracted by BAL 70 days after administration. Our data are in line with other clearance studies, demonstrating CFU of Bt kurstaki in the liver, spleen and lungs 21 days after intratracheal (i.t.) instillation and similar patterns were seen with Bt aizawai and B. subtilis. Clearance patterns after i.v. injection with 107 CFU per animal is also reported for Bt kurstaki, Bt israelensis, B. subtilis and B. sphaericus. All strains were still recovered from inner organs at the termination of the study (day 57 for Bt israelensis PLX3397 clinical trial and 128 for Bt kurstaki) [30, 31]. As Bt formulations are used for spray application, hazard identification and risk assessment should be based on airway effects. To our knowledge, the present study is the first to investigate airway irritation and airway inflammation induced
by inhalation of commercial Bt biopesticides. The i.t. instillation of biopesticide, showed that a single exposure gave rise to focal areas of lung tissue inflammation still detectable 70 days after exposure. A clear dose-response relationship was seen. Inflammation was also seen 70 days after repeated inhalation
of Bt biopesticide, although the effects after inhalation were less vigorous than after instillation. The sub-chronic inflammation was apparent as small patches of interstitial inflammation, a response that was not detectable in the corresponding fantofarone BAL fluid. The sub-chronic inflammation observed in the present study, was most likely due to the prolonged presence of Bt spores or other product residues in the lungs, triggering and maintaining the inflammatory response. This should be seen in the light that the formulated biopesticides contains only about 2% spores and 98% other ingredients according to manufacturer which makes long term inhalation studies using the final formulated biopesticide important. The list of other ingredients besides water is known to authorities (e.g. the EPA) and approved for other purposes e.g. a “”food- carbohydrate”" and preservatives . Most of these other ingredients have probably not been subjected to long term inhalation studies in animals as this was not their intended use. Therefore alternative inoculums or controls, including spore free or heat-inactivated biopesticide or specific excipients/additives should also be studied for biological effect.