Bacillus Flashcards
T/F: Anthrax can and has been used as a bioweapon
TRUE
What is the habitat of Bacillus spp?
saprophytes - dead or decaying organic matter, endospores allow for environmental persistence
What are the favorable soil conditions for Bacillus spp?
high moisture content, alkaline, rich in calcium and nitrogen
What species of Bacillus are important in veterinary medicine?
B. anthracis, B. cereus, B. licheniformis
What are some general characteristics of Bacillus spp?
gram-positive motile endospore-producing rods, aerobes or facultative anaerobes, catalase-positive and oxidase-negative, grow on non-enriched media,non-pathogenic
How do outbreaks of B. anthracis in herbivores occur?
pasture contamination by spores from buried animals, spores brought to surface by floor, excavation, subsidence
How do sporadic outbreaks of B. anthracis occur?
importation of contaminated meat- and bone-meal, fertilizers of animal origin, hides. raw/poorly-cooked contaminated meat fed to animals/people
How is B. anthracis transmitted?
mainly ingestion, inhalation, skin abrasions
What is the species susceptibility of B. anthracis?
ruminants > > > > horses > pigs > carnivores > birds (resistant)
What are the virulence factors of B. anthracis regulated by?
host temperature and CO2 concentration
What are the two major virulence factors of B. anthracis?
complex toxin, poly-y-D glutamic acid capsule
What is complex toxin encoded by?
pX01
What is poly-y-D glutamic acid capsule encoded by?
pX02
What are the three antigenic components of complex toxins?
protective antigen (host cell-binding portion for EF and LF), edema factor (an adenylyl cyclase enzyme), lethal factor (a zinc metalloprotease)
What are the effects of edema toxin?
increases cAMP, disturbs water homeostasis, accumulates fluid, targets neutrophils
What are the effects of lethal toxin?
causes death in macrophages, dendritic cells, neutrophils, and epithelial cells
What is the pathogenesis of B. anthracis?
cutaneous, intestinal, or pulmonary entry of spores -> regional lymph node -> regional hemorrhagic lymphadenitis -> septicemia or pulmonary lymphatic blockage -> meningitis or pulmonary edema -> death
What is the incubation period of B. anthracis?
3-7 days but ranges from 1-14 days
What are the clinical signs of B. anthracis in cattle and sheep?
death in animals with no premonitory signs, septicemia and rapidly fatal, pyrexia (fever), depression, congestion of mucosae
What are some post-mortem findings of cattle and sheep affected by B. anthracis?
rapid bloating, incomplete rigor mortis, ecchymotic hemorrhages, edema, dark, unclotted blood, blood-stained fluid in body cavities, enlarged soft spleen
T/F: necropsy of animals with anthrax is usually advised
FALSE
What are the major clinical signs of B. anthracis in pigs?
sudden death after ingestion, regional lymphadenitis (edematous swelling of throat/head ), intestinal dysentery (less common)
What are the major clinical signs of B. anthracis in carnivores?
resembles that of pigs
What are the major clinical signs of B. anthracis in herbivores?
resembles that of cattle
What are the major clinical signs of B. anthracis in horses?
extensive subcutaneous lesions, localized edema, septicemia with colic and dysentery
What does the cutaneous form of anthrax present as in humans?
localized lesions, itchy, red, dark blisters
What does the pulmonary/inhalation form of anthrax (woolsorters’ disease) present as in humans?
fever, pain, malaise, death in 1-7 days
What does the intestinal form of anthrax present as in humans?
death from contaminated meat
How do you diagnose anthrax?
blood sample (tail vein of ruminants or peritoneal fluid), MacFadyean reaction with polychrome methylene blue stain Loeffler’s stain, culture, PCR, fluorescent antibody technique, western blot and ELISA
What are the major microscopic characteristics of B. anthracis?
edge of colony has medusa hair appearance, spores stain with malachite green
What are some cultural characteristics of B. anthracis on nutrient agar?
irregularly round, raised, dull, and opaque colonies, frosted glass appearance
What are the major cultural characteristics of B. anthracis on blood agar with penicillin?
non-hemolytic
What test is utilized to diagnose B. anthracis in tissues?
ascoli’s test
T/F: B. anthracis grows on MAC agar
FALSE
How do you conduct an ascoli’s test?
2-3g of homogenized tissue in saline is boiled and filtered, filtrate used as an antigen in ring precipitation or gel diffusion test with specific antiserum
What are some general characteristics of B. anthracis spores?
require poor nutrient conditions and oxygen, very resistant to extremes and can survive for ~50 years, resistant to disinfectants and desiccation, lethal dose starting at 2,500 spores
How do you treat anthrax?
high doses of pencillin G or oxytetracycline
How do you control anthrax in endemic regions?
immediately report to authorities, annual vaccinations in cattle and sheep, killed vaccines in humans, chemoprophylaxis with long-acting penicillin
How do you control anthrax in non-endemic regions following an outbreak?
stop movement of animals, their waste, and bedding, wear PPE, sporicidal footbaths on farms, sanitization of contaminated buildings, incinerate carcasses, waste, and bedding, prevention of scavenger animals, isolation and observation of exposed animals
Where is B. cereus found?
soil, grains, vegetables, raw and processed foods
What is usually associated with B. cereus in animals?
embryonic death, abortion, and abnormal fetal development
What is usually associated with B. cereus in humans?
eye infections, foodborne intoxications, emetic syndrome, diarrheal syndrome
Where is B. licheniformis found?
environment, slurry, silage, and water troughs
What does B. licheniformis cause in cattle and sheep?
sporadic abortions
Where is B. licheniformis most commonly found?
housed, pit-silage-fed, spring calving beef cows last 2 months of pregnancy
T/F: Bacillus spp are large gram-positive rods
TRUE
T/F: B. anthracis is non-hemolytic in blood agar
TRUE
T/F: The genes of exotoxin production in B. anthraxis are present on bacterial chromosome
FALSE
T/F: veterinarians must always perform post-mortems on animals suspected to have died from anthrax
FALSE
T/F: B. anthracis does not produce capsules
FALSE
T/F: the protective antigen (PA) acts as a binding site for edema factor and lethal factor
TRUE
T/F: edema toxins target neutrophils
TRUE
