Applicability of UV resistant Bacillus pumilus endospores as a human adenovirus surrogate for evaluating the effectiveness of virus inactivation in low-pressure UV treatment systems

•Results show the applicability of endospores for UV CB performance testing.•The endospore propagation protocol exhibits a similar UV sensitivity to adenovirus.•UV tolerant B. pumilus endospores are a potential surrogate of human adenovirus.

Recent studies have demonstrated the potential to use Bacillus pumilus endospores as a surrogate for human adenovirus (HAdV) in UV disinfection studies. The use of endospores has been limited by observations of batch-to-batch variation in UV sensitivity. This study reports on a propagation method that utilizes a commercially available medium to produce UV tolerant B. pumilus endospores with a consistent UV sensitivity. It is further demonstrated that the endospores of B. pumilus strain (ATCC 27142), produced using this protocol (half strength Columbia broth, 5 days incubation, with 0.1 mM MnSO4), display a UV dose–response that is similar to that of HAdV. Endospore stocks could be stored in ethanol for up to two months at 4 °C without a significant change in UV sensitivity. Synergistic endospore damage was observed by pre-heat treatment of water samples followed by UV irradiation. UV tolerant B. pumilus endospores are a potential surrogate of HAdV for UV treatment performance tests in water utilities which do not have in-house research virology laboratories.