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Category: Clinical Microbiology
Bacillus and Other Aerobic Endospore-Forming Bacteria*, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817381/9781555817381.ch26-1.gif /docserver/preview/fulltext/10.1128/9781555817381/9781555817381.ch26-2.gifAbstract:
Aerobic endospore-forming bacteria are ubiquitous in nature. Because endospores are resistant to heat, desiccation, radiation, and disinfectants, they are found in terrestrial and aquatic habitats of all kinds and persist in places where most other organisms cannot. Dissemination of spores, via aerosols, wind, and dust, contributes to contamination of health care facilities, industrial clean rooms, and food production environments. Although commonly encountered in the microbiology laboratory, the majority of aerobic endospore-forming bacteria are nonpathogenic and of no clinical relevance. The few clinically significant species of Bacillus, Geobacillus, Lysinibacillus, Paenibacillus, and Brevibacillus are best described as opportunistic human pathogens. Transmission is restricted to ingestion, injection, injury, inhalation, or other contact with material that has been contaminated with spores or vegetative cells. Several environmental species are professional pathogens of invertebrates, and toxigenic strains of the Bacillus cereus group are an important cause of food poisoning, but only Bacillus anthracis is recognized as an obligate pathogen of animals. Clinical and laboratory expertise is a critical components of rapid anthrax diagnosis. Due to the biothreat potential of B. anthracis, many jurisdictions regulate possession and transportation of this agent, and testing requires enhanced safety precautions and training.
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(a) Gram stain of B. anthracis, associated with a bioterrorism attack, showing Gram-positive rods in peripheral blood buffy coat following admission of patient. Bar, 3 μm. (Courtesy of H. Masur.) (b) Spore-stained preparation of Bacillus cereus sporangia, viewed by bright-field microscopy. Spores are stained green, and vegetative cells are counterstained red. Bar, 2 μm. (Photograph kindly provided by M. Rodríguez-Díaz.) doi:10.1128/9781555817381.ch26.f1
(a) Gram stain of B. anthracis, associated with a bioterrorism attack, showing Gram-positive rods in peripheral blood buffy coat following admission of patient. Bar, 3 μm. (Courtesy of H. Masur.) (b) Spore-stained preparation of Bacillus cereus sporangia, viewed by bright-field microscopy. Spores are stained green, and vegetative cells are counterstained red. Bar, 2 μm. (Photograph kindly provided by M. Rodríguez-Díaz.) doi:10.1128/9781555817381.ch26.f1
Photomicrographs of endospore-forming bacteria viewed by bright-field microscopy (a) and phase-contrast microscopy (b to l). Bars, 2 μm. (a) B. anthracis, M’Fadyean stain showing capsulate rods in guinea pig blood smear; (b) B. cereus, broad cells with ellipsoidal, subterminal spores, not swelling the sporangia; (c) B. thuringiensis, broad cells with ellipsoidal, subterminal spores, not swelling the sporangia, and showing parasporal crystals of insecticidal toxin (arrows); (d) B. megaterium, broad cells with ellipsoidal and spherical, subterminal and terminal spores, not swelling the sporangia, and showing PHB inclusions (arrows); (e) B. subtilis, ellipsoidal, central and subterminal spores, not swelling the sporangia; (f) B. pumilus, slender cells with cylindrical, subterminal spores, not swelling the sporangia; (g) B. circulans, ellipsoidal, subterminal spores, swelling the sporangia; (h) Lysinibacillus sphaericus, spherical, terminal spores, swelling the sporangia; (i) Brevibacillus brevis, ellipsoidal, subterminal spores, one swelling its sporangium slightly; (j) Brevibacillus laterosporus, ellipsoidal, central spores with thickened rims on one side (arrow), swelling the sporangia; (k) Paenibacillus polymyxa, ellipsoidal, paracentral to subterminal spores, swelling the sporangia slightly; (l) Paenibacillus alvei, cells with tapered ends, ellipsoidal, paracentral to subterminal spores, not swelling the sporangium. doi:10.1128/9781555817381.ch26.f2
Photomicrographs of endospore-forming bacteria viewed by bright-field microscopy (a) and phase-contrast microscopy (b to l). Bars, 2 μm. (a) B. anthracis, M’Fadyean stain showing capsulate rods in guinea pig blood smear; (b) B. cereus, broad cells with ellipsoidal, subterminal spores, not swelling the sporangia; (c) B. thuringiensis, broad cells with ellipsoidal, subterminal spores, not swelling the sporangia, and showing parasporal crystals of insecticidal toxin (arrows); (d) B. megaterium, broad cells with ellipsoidal and spherical, subterminal and terminal spores, not swelling the sporangia, and showing PHB inclusions (arrows); (e) B. subtilis, ellipsoidal, central and subterminal spores, not swelling the sporangia; (f) B. pumilus, slender cells with cylindrical, subterminal spores, not swelling the sporangia; (g) B. circulans, ellipsoidal, subterminal spores, swelling the sporangia; (h) Lysinibacillus sphaericus, spherical, terminal spores, swelling the sporangia; (i) Brevibacillus brevis, ellipsoidal, subterminal spores, one swelling its sporangium slightly; (j) Brevibacillus laterosporus, ellipsoidal, central spores with thickened rims on one side (arrow), swelling the sporangia; (k) Paenibacillus polymyxa, ellipsoidal, paracentral to subterminal spores, swelling the sporangia slightly; (l) Paenibacillus alvei, cells with tapered ends, ellipsoidal, paracentral to subterminal spores, not swelling the sporangium. doi:10.1128/9781555817381.ch26.f2
Colonies of endospore-forming bacteria on blood agar (a to i) and nutrient agar (j to l) after 24 to 36 h at 37°C. Bars, 2 mm. (a) B. anthracis; (b) B. cereus; (c) B. thuringiensis; (d) B. megaterium; (e) B. pumilus; (f) Lysinibacillus sphaericus; (g) Brevibacillus brevis; (h) Brevibacillus laterosporus; (i) Paenibacillus polymyxa; (j) B. subtilis; (k) B. circulans; (l) Paenibacillus alvei. doi:10.1128/9781555817381.ch26.f3
Colonies of endospore-forming bacteria on blood agar (a to i) and nutrient agar (j to l) after 24 to 36 h at 37°C. Bars, 2 mm. (a) B. anthracis; (b) B. cereus; (c) B. thuringiensis; (d) B. megaterium; (e) B. pumilus; (f) Lysinibacillus sphaericus; (g) Brevibacillus brevis; (h) Brevibacillus laterosporus; (i) Paenibacillus polymyxa; (j) B. subtilis; (k) B. circulans; (l) Paenibacillus alvei. doi:10.1128/9781555817381.ch26.f3
Characters for differentiating some species of Bacillus, Geobacillus, and Paenibacillus a
Characters for differentiating some species of Bacillus, Geobacillus, and Paenibacillus a