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==Diagnostic Studies== | |||
Various techniques are used for the direct identification of ''B. anthracis'' in clinical material. Firstly, specimens may be [[Gram stain]]ed. ''Bacillus'' spp. are quite large in size (3 to 4 μm long), they grow in long chains, and they stain Gram-positive. To confirm the organism is ''B. anthracis'', rapid diagnostic techniques such as [[polymerase chain reaction]]-based assays and [[Immunofluorescence|immunofluorescence microscopy]] may be used.<ref>{{cite book |author=Levinson, W. |title=Review of Medical Microbiology and Immunology |year=2010 |edition=11th}}</ref> | |||
All ''Bacillus'' species grow well on 5% sheep blood agar and other routine culture media. Polymyxin-lysozyme-EDTA-thallous acetate can be used to isolate ''B. anthracis'' from contaminated specimens, and bicarbonate agar is used as an identification method to induce capsule formation. ''Bacillus'' spp. usually grow within 24 hours of incubation at 35°C, in ambient air (room temperature) or in 5% CO<sub>2</sub>. If bicarbonate agar is used for identification, then the medium must be incubated in 5% CO<sub>2</sub>. ''B. anthracis'' colonies are medium-large, gray, flat, and irregular with swirling projections, often referred to as having a "[[Medusa|medusa head]]" appearance, and are not hemolytic on 5% sheep blood agar. The bacteria are not motile, susceptible to penicillin, and produce a wide zone of lecithinase on egg yolk agar. Confirmatory testing to identify ''B. anthracis'' includes gamma bacteriophage testing, indirect hemagglutination, and enzyme linked immunosorbent assay to detect antibodies.<ref>{{cite book |author=Forbes, B.A. |title=Bailey & Scott's Diagnostic Microbiology |year=2002 |edition=11th}}</ref> The best confirmatory precipitation test for anthrax is the [[Alberto Ascoli|Ascoli]] test. | |||
==References== | ==References== | ||
Revision as of 18:21, 16 July 2014
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Diagnostic Studies
Various techniques are used for the direct identification of B. anthracis in clinical material. Firstly, specimens may be Gram stained. Bacillus spp. are quite large in size (3 to 4 μm long), they grow in long chains, and they stain Gram-positive. To confirm the organism is B. anthracis, rapid diagnostic techniques such as polymerase chain reaction-based assays and immunofluorescence microscopy may be used.[1]
All Bacillus species grow well on 5% sheep blood agar and other routine culture media. Polymyxin-lysozyme-EDTA-thallous acetate can be used to isolate B. anthracis from contaminated specimens, and bicarbonate agar is used as an identification method to induce capsule formation. Bacillus spp. usually grow within 24 hours of incubation at 35°C, in ambient air (room temperature) or in 5% CO2. If bicarbonate agar is used for identification, then the medium must be incubated in 5% CO2. B. anthracis colonies are medium-large, gray, flat, and irregular with swirling projections, often referred to as having a "medusa head" appearance, and are not hemolytic on 5% sheep blood agar. The bacteria are not motile, susceptible to penicillin, and produce a wide zone of lecithinase on egg yolk agar. Confirmatory testing to identify B. anthracis includes gamma bacteriophage testing, indirect hemagglutination, and enzyme linked immunosorbent assay to detect antibodies.[2] The best confirmatory precipitation test for anthrax is the Ascoli test.