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Brucella

Brucella. Six species of Brucella B.melitensis, B.abortus, B.suis, B.canis Sir David Bruce [brucellosis] , Bernhard Bang [Bang's disease] Undulant fever, Malta fever, Mediterranean remittent fever . Brucella.

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Brucella

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  1. Brucella Six species of Brucella B.melitensis, B.abortus, B.suis, B.canis Sir David Bruce [brucellosis], Bernhard Bang [Bang's disease] Undulant fever, Malta fever, Mediterranean remittent fever

  2. Brucella • small (0.5 × 0.6 to 1.5 μm), nonmotile, nonencapsulated, gram-negative coccobacilli • grows slowly • strictly aerobic • does not ferment carbohydrates

  3. Brucella • endotoxin is less toxic • intracellular parasite • the organisms are phagocytosed by macrophages and monocytes • phagocytosed bacteria are carried to the spleen, liver, bone marrow, lymph nodes • the bacteria secrete proteins that induce granuloma formation

  4. Brucella • Intracellular pathogen that is resistant to killing in serum and by phagocytes • Smooth colonies associated with virulence • goats and sheep (Brucella melitensis) • cattle (Brucella abortus) • swine (Brucella suis) • dogs, foxes (Brucella canis)

  5. Brucella • Latin America, Africa, the Mediterranean basin, the Middle East, and Western Asia • More than 500,000 documented cases • Vaccination of animals • Direct contact with the organism (e.g., a laboratory exposure), ingestion (e.g., consumption of contaminated food products), or inhalation

  6. Brucella • Brucella causes mild or asymptomatic disease in the natural host • Erythritol (breast, uterus, placenta) • Brucellae are shed in high numbers in milk, urine, and birth products • B.melitensis is the most common spp

  7. Brucella-Clinical diseases • Brucellosis: Initial nonspecific symptoms of malaise, chills, sweats, fatigue, myalgias, weight loss, arthralgias, and fever; can be intermittent (undulant fever) • can progress to systemic involvement (gastrointestinal tract, bones or joints, respiratory tract, other organs)

  8. Brucella-Clinical diseases • Incubation period 1-6 weeks • Fever rises in the afternoon • Falling at night by drenching sweat • Lymph nodes enlarge, SM • Hepatitis, steomyelitis • Generalized infection subsides usually • A chronic state may occur

  9. Brucella-Diagnosis • grow slowly • most enriched blood agars • microscopic and colonial morphology • positive oxidase and urease reactions • B. abortus and B. melitensis, B. abortus, and B. suis will react with antisera prepared against B. abortus or B. melitensis

  10. Brucella-Serology • IgM, IgG, IgA • Four fold increase or 1/80 indicate active infection • If agglutination negative “blocking antibodies” add antihumanglobulin

  11. Brucella-Treatment • Doxycycline+rifampin • Trimethoprim-sulfamethoxazole for pregnant women and for children younger than 8 years • 6 weeks or longer • Fluoroquinolones, macrolides, penicillins, and cephalosporins either ineffective or have unpredictable activity.

  12. Francisella • Two species, Francisella tularensis and Francisella philomiragia • the causative agent of tularemia (also called glandular fever, rabbit fever, tick fever, and deer fly fever) in animals and humans

  13. very small (0.2 × 0.2 to 0.7 μm), faintly staining, gram-negative coccobacillus • nonmotile • thin lipid capsule • fastidious requirements (most strains require cysteine for growth) • strictly aerobic and requires 3 or more days

  14. Gram stain of Francisella tularensis isolated in culture; note the extremely small coccobacilli

  15. Antiphagocytic capsule • Intracellular pathogen resistant to killing in serum and by phagocytes • Wild mammals, domestic animals, birds, fish, and blood-sucking arthropods are reservoirs; rabbits and hard ticks are most common hosts; humans are accidental hosts • Worldwide distribution • The infectious dose is very small

  16. Human tularemia is acquired most often from the bite of an infected "hard-shell" tick (e.g., Ixodes, Dermacentor, Ambylomma spp.) • or from contact with an infected animal or domestic pet • F. tularensis requires as few as 10 organisms when exposure is by an arthropod bite

  17. Ulceroglandular tularemia: Painful papule develops at the site of inoculation that progresses to ulceration; localized lymphadenopathy • Oculoglandular tularemia: Following inoculation into the eye (e.g., rubbing eye with a contaminated finger), painful conjunctivitis develops with regional lymphadenopathy • Pneumonic tularemia: Pneumonitis with signs of sepsis develops rapidly after exposure to contaminated aerosols; high mortality unless promptly diagnosed and treated

  18. Ulceroglandular tularemia is the most common manifestation

  19. Francisella-Diagnosis • F. tularensis are hazardous for both the physician and the laboratory worker • Microscopy is insensitive due yo small size and faintly staining • Fluorescein-labeled antibodies • PCR • F. tularensis can grow on chocolate agar or buffered charcoal yeast extract (BCYE) agar, media supplemented with cysteine • a fourfold or greater increase in the titer of antibodies during the illness or a single titer of 1:160 or greater

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