A survey of the occurrence of Bacillus anthracis in North American soils over two long-range transects and within post-Katrina New Orleans Dale W. Griffin a, * , Terry Petrosky a , Suzette A. Morman b , Vicki A. Luna c a US Geological Survey, 2010 Levy Avenue, Suite 100, Tallahassee, FL 32310, USA b US Geological Survey, MS 964D, Denver Federal Center, Denver, CO 80225, USA c University of South Florida, Center for Biological Defense, Tampa, FL 33612, USA article info Article history: Available online 3 May 2009 abstract Soil samples were collected along a north–south transect extending from Manitoba, Canada, to the US– Mexico border near El Paso, Texas in 2004 (104 samples), a group of sites within New Orleans, Louisiana following Hurricane Katrina in 2005 (19 samples), and a Gulf Coast transect extending from Sulphur, Lou- isiana, to DeFuniak Springs, Florida, in 2007 (38 samples). Samples were collected from the top 40 cm of soil and were screened for the presence of total Bacillus species and Bacillus anthracis (anthrax), specifi- cally using multiplex-polymerase chain reaction (PCR). Using an assay with a sensitivity of 170 equiv- alent colony-forming units (CFU) g 1 field moist soil, the prevalence rate of Bacillus sp./B. anthracis in the north–south transect and the 2005 New Orleans post-Katrina sample set were 20/5% and 26/26%, respec- tively. Prevalence in the 2007 Gulf Coast sample set using an assay with a sensitivity of 4 CFU g 1 of soil was 63/0%. Individual transect-set data indicate a positive relation between occurrences of species and soil moisture or soil constituents (i.e., Zn and Cu content). The 2005 New Orleans post-Katrina data indi- cated that B. anthracis is readily detectable in Gulf Coast soils following flood events. The data also indi- cated that occurrence, as it relates to soil chemistry, may be confounded by flood-induced dissemination of germinated cells and the mixing of soil constituents for short temporal periods following an event. Published by Elsevier Ltd. 1. Introduction Bacillus anthracis is an aerobic, gram-positive, endospore- forming, rod-shaped bacterium and was first described as the causative agent of anthrax in a paper published by Robert Koch in 1876 (Koch, 1876). B. anthracis is a common community mem- ber of many soil environments and has been shown to germinate and survive in the rhizosphere (root zone) of grasses (Van Ness and Stein, 1956; Saile and Koehler, 2006). B. anthracis occurs in two states, a vegetative or growing state and as a spore state. Formation of spores is a long-term environmental survival strat- egy and is activated when actively growing cells experience stress, such as the depletion of nutrients experienced when mov- ing from the blood of a host to soil (Titball et al., 1991). Surveil- lance and survival studies have shown that, although only a fraction (10%) of a Bacillus sp. soil inoculum may survive after more than 60 days of incubation, spores are detectable in the top few centimeters for many years (West and Burges, 1985; Man- chee et al., 1994). A 1979 and early 1980s survey of B. anthracis spores on the Island of Gruinard (Scotland) detected viable test- strain spores that were released during open-air experiments during World War II (Manchee et al., 1994). Spores provide pro- tection in the most adverse environments (extremely low humidity, high ultraviolet exposure, heat, etc.), and researchers have speculated that a spore-forming bacterium could survive interplanetary transport and, if shielded within a particle, inter- stellar transport (Stein and Rodgers, 1945; Stein and Rogers, 1946; Nicholson et al., 2000; Setlow, 2001). While B. anthracis spores usually occur in highest concentration in areas around the remains of infected animals, it is believed that the probabil- ity of acquiring infection from exposure to spore-laden soils is low (Turnbull et al., 1998). This pathogen typically infects herbivores through ingestion or inhalation during grazing and, in turn, can pass the disease to car- nivores through consumption (Stein, 1945, 1950). The occurrence of outbreaks in herbivores following heavy-precipitation events is well documented (Patra et al., 1998; Parkinson et al., 2003). Hu- man infections in the USA are rare, but occurrences are more fre- quent on a global scale (Holty et al., 2006). Human cases are usually occupational in nature, resulting from exposure to contam- inated hides, hairs and meats (Stein, 1953). The three types of infections are known as cutaneous, gastrointestinal and pulmon- ary. Human fatality rates for untreated cases of the three types of infections are approximately 20%, 25–60% and 100%, respectively 0883-2927/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.apgeochem.2009.04.016 * Corresponding author. E-mail address: dgriffin@usgs.gov (D.W. Griffin). Applied Geochemistry 24 (2009) 1464–1471 Contents lists available at ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem