Bacillus anthracis spore interactions with mammalian cells: Relationship between germination state and the outcome of in vitro

Abstract

BackgroundDuring inhalational anthrax, internalization of Bacillus anthracis spores by host cells within the lung is believed to be a key step for initiating the transition from the localized to disseminated stages of infection. Despite compelling in vivo evidence that spores remain dormant within the bronchioalveolar spaces of the lungs, and germinate only after uptake into host cells, most in vitro studies of infection have been conducted under conditions that promote rapid germination of spores within the culture medium.ResultsUsing an in vitro model of infection, we evaluated the influence of the germination state of B. anthracis spores, as controlled by defined culture conditions, on the outcome of infection. Spores prepared from B. anthracis Sterne 7702 germinated in a variety of common cell culture media supplemented with fetal bovine serum (FBS) while, in the absence of FBS, germination was strictly dependent on medium composition. RAW264.7 macrophage-like cells internalized spores to the same extent in either germinating or non-germinating media. However, significantly more viable, intracellular B. anthracis were recovered from cells infected under non-germinating conditions compared to germinating conditions. At the same time, RAW264.7 cells demonstrated a significant loss in viability when infected under non-germinating conditions.ConclusionsThese results suggest that the outcome of host cell infection is sensitive to the germination state of spores at the time of uptake. Moreover, this study demonstrates the efficacy of studying B. anthracis spore infection of host cells within a defined, non-germinating, in vitro environment.

Anthrax SET Protein

“…Time Course of Macrophage Infection of Sterne-The Raw 264.7 mouse macrophage cell line was grown in MEM media with 10% FBS until reaching a confluency of ϳ90% (42,43). The media was aspirated, and cells were washed three times with MEM media without FBS.…”

Germination and Amplification of Anthrax Spores by Soil-Dwelling Amoebas

“…Human infection with B. anthracis is typically zoonotic and initiates through one of four possible routes: ingestion, cutaneous exposure, parenteral injection, or inhalation, the last being the most lethal and of greatest concern when B. anthracis is weaponized. Anthrax spores germinate and multiply within macrophages (10)(11)(12)19). Infection of hosts is mediated in large part by factors encoded on the two large virulence plasmids pX01 (GenBank accession number NC_012579) and pX02 (GenBank accession number NC_012577).…”

Simple detection of Bacillus anthracis spores by precipitation method with goat antibody anti anthrosa

“…40 Rapid germination of Bacillus anthracis spores is induced by serum that is commonly supplemented in cell culture growth formulations; however, some serum-free growth media formulations can also induce Bacillus anthracis germination. 41,42 Anthrosa precipitation of Bacillus anthracis with goat antibody anti anthrosa showed a lot of whitish, while the Bacillus cereus are not many shows a whitish color (Figure 3). The result meant that test positive precipitation occurs in Bacillus anthracis, while the Bacillus cereus precipitation test negative.…”