Characteristics of Spore Germination in a Mouse Model of Cutaneous Anthrax
Division of Infectious Diseases, Department of Medicine, Medical College of Wisconsin, and Consultant Care Division and Research Service, Milwaukee Veterans Affairs Medical Center, Milwaukee
Background.
Cutaneous infection is the most common form of human anthrax, but little is known about Bacillus anthracis spore germination in these infections.
Methods.We used experimental inoculations of B. anthracis Sterne spores or vegetative bacilli onto intact or abraded mouse flank skin, followed by evaluation of the infections and enumeration of germinating spores and vegetative bacilli.
Results.Bacilli developed from a spore inoculum after application onto abraded, but not intact, skin of the mice. Germination appeared to occur extracellularly at the skin surface before the development of a phagocytic response; in fact, vegetative bacilli were seen after inoculation of the spores on top of a filter that separated them from the host phagocytic cells below. Malachite green staining demonstrated that spores began germinating 1–3 h after inoculation onto abraded skin. Vegetative bacilli were found not to be capable of initiating infection in the absence of cutaneous abrasion.
Conclusions.The results indicate that epidermal damage is required for germination of B. anthracis spores in these infections; even so, spore germination by itself is not sufficient to produce infection of undamaged skin. In contrast to events in experimental inhalational anthrax, spore germination in these cutaneous infections appears to occur extracellularly.
Received 11 August 2006; accepted 29 October 2006; electronically published 2 February 2007.
Cited by
Online publication date: 1-Jul-2008.
CrossRef
-
Potential conflicts of interest: none reported.
Presented in part: 44th Annual Meeting of the Infectious Diseases Society of America, Toronto, Canada, 12–15 October 2006 (abstract 347).
Financial support: Department of Veterans Affairs (VAMR 8033‐17).