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Published byDebra Perry Modified over 8 years ago
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Gram +, large rodoxidase - endosporecatalase + mostly motileoxidative/ fermentative aerobic Habitat widely distributed in the environment because they produce highly endospore
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Bacillus anthracis * spore can survive more than 50 years in soil * the plasmid-encoded capsule consist of D-glutamyl polypeptide * plasmid encodes exotoxin * cell wall is largely polysaccharide Anthrax
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Virulence factor 1. Capsular antigen * D-glutamyl polypeptide capsule antiphagocyte * capsule establishes infection * non encapsulated mutants are avirulent 2. Exotoxin (protein toxin, heat labile) 3 components
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Components of exotoxin Pathogenic Character loss fluidedema release IL-1 from macrophage antiphagocytic cytotoxin of cells death of target cell Factor I FractionName lethal factor II+III edema factor I+II protective antigen Factor II Factor III
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Resistance * spore are killed by : autoclaving (121 0 C / 15 min) dry heat (150 0 C / 60 min) boiling (100 0 C > 10 mins) * not susceptible to : phenolic compound alcohol quarternary ammonium disinfectant
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Resistance (cont.) * susceptible to : aldehyde ß -propiolactone chlorineethylene oxide * heat fixation of smear does not kill spores
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TRANSMISSION animal:ingestion of contaminated feed or water wound infection and arthropod bites humans:skin, wound (malignant carbuncle) inhalation ingestion
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PATHOGENESIS AND PATHOGENICITY in vivo * gene encoding capsule and toxins are turned on * antiphagocytic capsule and three toxins * toxin is leukocidal * increase vascular permeability and capillary thrombosis leading to shock related to generalize release of IL – 1
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spores germinate in macrophage phagosomal escape replicate & release from macrophage encapsulated bacteria proliferate and resist further phagocytosis
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spread to regional lymph nodes reticuloendothelial organs bacteremia and toxaemia pathophysiological effect shock asphyxia death hemorrhagic lymphadinitis
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Description: How
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Infection in domestic animals Bovine and ovine : (septicemic form) peracute septicemia (death within 1-2 hr.) acute septicemia (death in 49-96 hr.) chronic infection (rarely observed) Equine : (subacute to acute) * colic and diarrhea * edema at the point of infection (intestine, throat) * acute pharyngitis
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Porcine: * infected meat & bone meal * pharyngitis is most common * regional lymphadinitis * cutaneous anthrax “ bull nose ” Canivores: * infected meat * pharyngeal anthrax * similar to porcine * septicemia may occur by tainted meat
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Human * percutaneous introduction (malignant carbuncle) * possible subcataneous edema and septicemia * pulmonary edema (inhalation anthrax) hemorrhagic pneumonia meningitis
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Vesicle ringBlack eschar
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day 2 day 4
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ISOLATION AND IDENTIFICATION Sample Collection : * blood aspirated from superficial vessels * aqueous humor * bloody discharges from orifices (direct exam.) * spleen (if carcass was opened)
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Direct examination : Blood and organ smears : Gram stain Capsule stain encapsulated, gram+, non-spore, rod FA technique
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Culture : common media flat dry “ medusa head ” colonies non-hemolysis, non-motile Animal inoculation (mice, guinea pig) : subcutaneous inoculation of suspected materials hemorrhage, gelatinous exudate at that site engorged spleen encapsulated agent demonstrated in blood and tissues
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Immunodiagnosis : Ascoli ’ s test precipitation test Molecular methods : DNA probes, PCR detect specific genes in plasmid-encoded capsule and toxin
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Precipitation test
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(1) opportunistic infections abortion in cattle mastitis (acute gangrenous) initiators (2) Food poisoning in humans diarrhea (various foods - diarrheal toxin) vomiting (rice - emetic toxin) Bacillus cereus Udder surgery intramammary medications
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widespread in the environment associated with food spoilage cause of abortion in cattle & sheep (silage & mouldy hay) diagnostic significance when isolated in heavy pure culture from foetal abomasal contents Bacillus licheniformis
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