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27 Cards in this Set
- Front
- Back
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General characteristics of Brucella? |
Small Gram Neg, Coccobacilli - Don't stain well; use alternative Koster's stain & some require CO2 for growth - Non-motile, non-sporing - Non-fermentative - AEROBE - Oxidase positive - Species separated by growth characteristics & serotyping - Predilection for reproductive tracts of animals - HIGHLY ZOONOTIC (potential biowarfare agent) |
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Brucella infections typically occur within the ______________ tracts of animals. |
REPRODUCTIVE TRACTS - Most species cause abortion, orchitis and occasionally epididymitis & arthritis |
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Pathogenesis of Brucella spp? |
1. Bacteria penetrates the mucosa 2. Travels to regional lymph node (LN) 3. Avoids phagocytosis - Prevents fusion of phagolysosomes, avoiding immune response. 4. Persistence - bacteraemia 5. Dissemination throughout body - RES persistence, testis, udder, uterus & abortion (placentitis) |
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Unique characteristics of brucella melitensis? |
TWO CHROMOSOMES - Type IV secretion system - much like type III SS but no homologous structure |
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Virulence factors of brucella spp? |
Very little known... - Intracellular pathogen - Survives within macrophages (inhibits phagolysosome fusion) - Type IV secretion system - Tissue tropism - cells of host support bacteria - Siderophore (iron uptake system) - Doesn't alarm the host immune system, allowing time to become intracellular |
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Great Britain has eradicated bovine brucellosis.
True or False? |
TRUE - Vaccine scheme eradicated it, but unknown abortions of cattle and sheep are suspect of brucella - imported from N. Ireland. |
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Describe Human Brucellosis. |
LEADING ZOONOSIS WORLDWIDE - Infection via contact with infected animals or consumption of their products (non-pasteurized milk or cheese) |
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Describe methods of Brucella screening. |
Usually serology - Detect antibody in serum(milk) against Brucella LPS TESTS: - Milk ring test - Rose Bengal plate test - ELISA - Serum agglutination Test (SAT) * Beware false positives: antibodies cross react with LPS of other bacteria, yersinia entercolitica |
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Vaccines available for Brucella? |
"Smooth" Strains for ruminants "Rough" Strains for cattle
Problems: INFECTIOUS IN HUMANS - self-inoculations = nasty infection |
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General characteristics of Bordetella? |
Small, gram neg coccobacilli - Strict anaerobe - Oxidase positive - Non-sporting - Most motile - Don't ferment carbs = can't identify with API NF - RESPIRATORY TRACT PATHOGENS (mammals & birds) |
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Most important brucella spp to note? |
Brucella abortis (ruminants) & B. melitensis (sheep, goats)
Both zoonotic potential! |
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Most important bordetella spp to note? |
B. Bronchiseptica - dogs, cats, pigs (many spp) = respiratory infections & atrophic rhinitis (pigs)
B. pertussis - humans, non-zoonotic = whooping cough |
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Identifiable feature of Bordetella bronchiseptica? |
1. Grows on MacConkey, but Non-lactose fermenter (NLF) = clear, non-pink colonies * Useful for identifying most gram neg respiratory pathogens! 2. Appearance of yellow fringe on surface of respiratory epithelium, coating the cilia cells and causing mucous buildup |
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Virulence strategies of Extracellular pathogens (e.g. bordetella)? |
1. Counteract complement 2. Counteract phagocytes 3. Acquire nutrients |
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Pathogenesis of bordetella infections? |
E.g. Bordetella bronchiseptica: 1. Initial attachment of B. bronchiseptica to ciliated cells of respiratory epithelium 2. Tight adhesion to cilia, production of toxins & paralysis of cilia 3. Loss of cilia - interference with innate and specific immune response = accumulation of mucous |
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Virulence factors of Bordetella? |
1. Adhesins = sticky; attach to host tissues - fimbriae - filamentous haemagglutinin (FHA) - pertactin 2. Type III Secretion System (TTSS) 3. Toxins = tissue damage & counteract host defenses - Adenylate cyclase toxin = RTX toxin binds to adenylate cyclase, preventing it's penetration into host cell; thus interfering with phagocytosis & chemotaxis - Tracheal cytotoxin = loss of cilia in respiratory tract - Dermonecrotic toxin * Expression of VFs dependent on temp (37C) |
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Describe the process of regulation of Bordetella virulence. |
Bordetella contains two genes which regulate expression of virulence factors: BvgS & BvgA - When B. bronchiseptica is taken up by host, th temp goes up (37C) = BvgS activates BvgA by phosphorylation and the virulence factors are expressed - When not within the host, the temp will be lower (25C), and BvgA will become unphosphorylated & virulence genes not expressed |
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Pathogenesis of Atrophic rhinitis? |
1. Initial attachment of B. bronchiseptica to ciliated cells of respiratory epithelium 2. Tight adhesion to cilia, production of toxins & paralysis of cilia 3. Loss of cilia - interference with innate and specific immune response = accumulation of mucous 4. Colonization with toxigenic Pasteruella Multocida types A or D = destruction of turbinates! |
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Vaccines against B. bronchiseptica? |
INTRANASAL, Live attenuated available for cats & dogs - Mucosal IgA important for immunity |
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General characteristics of anaerobes? |
ANAEROBIC (no oxygen) Gram negative rods (although varies) - Commensal of mucous membranes; opportunistic; infections often polymicrobial - Non-sporing - Negative redox - Cultured anaerobically & identified with API anaerobe - Lesions foul smelling! - They can grow in the lumen of the LI and the rumen Elsewhere they require: * Loss of blood supply or * Necrotic conditions * Population of aerobes/facultative anaerobes which reduce oxygen tension |
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Describe handling of anaerobic cultures. |
- Samples submitted in transport medium - Handled in absence of oxygen - Streaked on horse blood agar or fastidious anaerobe agar - Incubated in anaerobic incubator |
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Describe typical polymicrobial infections and the bacteria that cause them. |
1. FOOT ROT - Dichelobacter nodosus = gram - anaerobe - Fusobacterium necrophorum = gram - anaerobe - Arcanobacterium pyogenes = gram + actinobacteria 2. ABSCESSES - Bacteriodes fragilis = gram - anaerobe - E. coli = gram - enterobacteriacaea |
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Pathogenesis of foot rot? |
Predisposing conditions: wetting, trauma, etc 1. Primary colonization by facultative anaerobe (e.g. A. pyogenes) 2. Secondary colonization by strict anaerobe (F. necrophorum) 3. Local superficial inflammation = dermatitis 4. Tertiary colonization by another anaerobe (Dichelobacter nodosus) = severe inflammation 5. Ulceration & hoof destruction 6. Chronic lameness :( * Possibly other bacteria involved |
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General characteristic of Dichelobacter nodosus? |
Strict anaerobe, Gram negative - Non-sporing rods - Long clubbed ends - Major cause of foot rot in sheep - Virulence factors: 1. Type IV fimbriae (distinct feature under micro); used as target in vaccines 2. Several proteases |
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Briefly describe fusobacterium necrophorum. Infections caused? |
Gram negative pleomorphic rods, obligate anaerobe - Non-sporing - Often part of a mixed infection (foot rot) - Infections caused: 1. Cattle: calf diphtheria, post-partum metritis, hepatic abscesses 2. Pig: Necrotic rhinitis (bull nose) 3. Horses: Necrobacilliosis of lower limb; thrush of hoof |
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Virulence factors of Fusobacterium? |
1. Leukotoxins 2. Haemolysins 3. Proteases |
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General characteristics of obligate anaerobes: Bacteroides sp Prevotella sp Porphyomonas sp |
GRAM NEGATIVE RODS - All pyogenic and may cause abscesses, soft tissue infections and foul smelling pus
* Some bacteroides fragilis strains produce an enterotoxin & can cause diarrhea in young animals (lambs, calves, foals, piglets) |
