Hot air hand dryers in multiple men's and women's bathrooms in 3 basic science research areas in an academic health center were screened for their deposition on plates of: i) total bacteria, some of which were identified; and ii) a kanamycin resistant strain, PS533, spores of which are produced in large amounts in one basic science research laboratory. Plates exposed to hand dryer air for 30 seconds averaged 18-60 colonies/plate but interior hand dryer nozzle surfaces had minimal bacterial levels, plates exposed to bathroom air for 2 minutes with hand dryers off averaged ≤1 colony, and plates exposed to bathroom air moved by a small fan for 20 minutes had averages of 15 and 12 colonies/plate in two buildings tested. Retrofitting hand dryers with HEPA filters reduced bacterial deposition by hand dryers ∼4-fold, and potential human pathogens were recovered from plates exposed to hand dryer air whether or not a HEPA filter was present, and from bathroom air moved by a small fan. Spore-forming colonies, identified as PS533 averaged ∼2.5-5% of bacteria deposited by hand dryers throughout basic research areas examined regardless of distance from the spore forming laboratory, and these were almost certainly deposited as spores. Comparable results were obtained when bathroom air was sampled for spores. These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers, and that spores could be dispersed throughout buildings and deposited on hands by hand dryers. While there is evidence that bathroom hand dryers can disperse bacteria from hands or deposit bacteria on surfaces, including recently washed hands, there is less information on: i) the organisms dispersed by hand dryers; ii) if hand dryers provide a reservoir of bacteria or simply blow large amounts of bacterially contaminated air; and iii) if bacterial spores are deposited on surfaces by hand dryers. Consequently, this study has implications for the control of opportunistic bacterial pathogens and spores in public environments including healthcare settings. Within a large building, potentially pathogenic bacteria including bacterial spores may travel between rooms, and subsequent bacterial/spore deposition by hand dryers is a possible mechanism for spread of infectious bacteria including spores of potential pathogens if present.

Aims To determine how the microbicide ceragenin‐13 (CSA‐13) kills Bacillus subtilis spores prepared on growth or sporulation media, and these spores’ properties. Methods and Results Spores made on Luria broth (LB) growth or double‐strength Schaeffer’s‐glucose (2xSG) sporulation plates found that spores made on LB plates have coat defects as evidenced by their lower hypochlorite resistance, faster germination with dodecylamine and slower germination with Ca2+‐dipicolinic acid (CaDPA) than 2xSG plate spores. CSA‐13 triggered CaDPA release from spores, an early step in germination, but only well at 70°C and better with spores made on LB than on 2xSG plates. Approximately 90% of spores with elevated levels of SpoVA proteins that form a CaDPA release channel, released CaDPA with CSA‐13 at 70°C, and faster with spores made on LB than 2xSG plates. Levels of CSA‐13 killing of spores made on LB and 2xSG plates were similar to levels of CaDPA release triggered by this agent. Conclusions CSA‐13 kills bacterial spores, but only at high concentrations and temperatures, and is preceded by CaDPA release. Significance and Impact of the Study CSA‐13 is not a direct sporicide as reported previously, but most likely germinates spores via activation of spores’ CaDPA channel, albeit inefficiently, and then killing the germinated spores.