Transcript Zoonosis
Yersinia Brucella Zoonosis Francisella ZOONOSIS A disease, primarily of animals, which is transmitted to humans as a result of direct or indirect contact with the infected animal population Brucellosis 1. Overview 4. Symptoms 2. Morphology & 5. Pathogenesis Physiology 6. Diagnosis 3. Epidemiology 7. Treatment Brucella: Overview • Primarily a disease of animals. • Common where significant disease among domestic animals. • Common names- Undulant fever, Malta fever, Mediterranean remittent fever. • Brucella can go through intact skin. • Facultative intracellular bacteria Morphology & Physiology • Small gram-negative coccobacillus • Grows slowly (7 days), at 370 C. • On subculture, a minimum of 48 h growth • Aerobic growth on Chocolate agar and Sheep blood agar • Will not grow on MacConkey or Eosin methylene blue (EMB) agar Morphology & Physiology • Non-pigmented and non-hemolytic • Non-motile • Oxidase: positive • Catalase: positive • Urease: strongly positive, less than 2 hours. Some species within 5 minutes. Microscopic Characteristics • Brucella spp. – poorly staining – small gram-negative coccobacilli – seen mostly as single cells – appearing like “fine sand” Brucella melitensis colonies A. Grows slowly on most standard laboratory media. Usually not visible at 24h. B. Pinpoint, smooth, translucent, nonhemolytic at 48h. Public Health Aspects Brucella: Sources • Brucellosis caused by 1 of 4 Brucella species: 1. B. abortus Some strains require 5% CO2 on initial isolation. 2. B. melitenus Sheep Camels Goats 3. B. suis 4. B. canis 2 patient populations 1. Individuals who work with unvaccinated animals • B. abortus and B. suis • Infections result from: • direct contact • inhalation 2. Individuals who ingest unpasteurized dairy products • B. melitensis is the most common agent Host Animal - Brucellosis • Asymptomatic or mild disease. • Predilection for organs rich in erythritol (breast, uterus, placenta, epididymis). • Causes sterility, abortions or carrier state in nonhuman animals. Human - Brucellosis Symptoms Acute Phase Advanced Disease Chronic Form Pathogenesis Brucella mucosal epithelium Transported to lymph nodes, spleen, liver and bone marrow. Pathogenesis Lysozome X Phagosome Pathogenesis • No exotoxins • LPS does not activate the alternative complement pathway • Acute lymphadenitis • Granulocyte production in lymphatic tissue, spleen, liver, bone marrow, lymph nodes and kidneys. • A potential bioterrorist agent Diagnosis • Symptoms and history • Serological agglutination tests • Culture – Blood and bone marrow cultures – Spleen, liver, joint fluid or abscesses Treatment Tetracycline, doxycycline, or trimethoprimsulfamethoxazole in combination and rifampin or gentamicin for 6 weeks to prevent reoccurring infection. Tularemia: (Francisella tularensis) Gram stain Tularemia: Overview • Primary reservoir in US – Rabbits and muskrats • Insect vectors – Ticks • Infection via – – – – – Insect bites Handling contaminated animal tissues Inhalation of aerosols Ingestion of contaminated food or water Exposure in a laboratory setting Tularemia: Overview • Gram-negative coccobacilli. • Low infectious dose • Two subspecies of F. tularensis: – subspecies tularensis (type A) – subspecies holarctica (type B) Morphology & Physiology • Tiny gram-negative coccobacillus • Nonmotile, encapsulated • Aerobic slow growing (48 hours) 35-370 C • Fastidious organism requires sulfhydryl (cysteine, IsoVitaleX) supplementation for growth • Grows wells on – Chocolate agar – Buffered charcoal yeast extract agar Colony Characteristics • After 48 hours incubation • Colonies – Very small – white to gray to bluishgray • Will not grow on MacConkey or EMB plates. F. tularensis on chocolate agar 48 hours growth. Microscopic Characteristics Tiny, faintly staining, pleomorphic gram-negative rods (0.2-0.5 mcm X 0.7-1.0 mcm) are noted; cells are smaller than those of Haemophilus species. Phenotypic Characteristics • Grows slowly at 35-370 C • Oxidase-negative • Weakly catalase-positive (may be negative) • Urea-negative • Nitrate-negative • Non-motile • Beta-lactamase-positive • Satellite or XV test-negative (unlike Haemophilus) Tularemia: Public Health • Modes of humans infection • Bite of infected flies, or ticks • Handling contaminated animal tissues or fluids • Direct contact with or ingestion of contaminated water, food, or soil • Inhalation of infective aerosols (most likely BT route) Tularemia: Public Health • Endemic in US – Majority of cases occur May – September (tick exposure) or winter (hunters). – Most in rural areas. – Arkansas, Missouri and Oklahoma Symptoms • Incubation period: 3-5 days (range 1-21 days) • Clinical presentation can be divided into groups – Ulceroglandular (45-85%) /glandular (10% to 25%) – Typhoidal – Pneumonic – Oculoglandular – Oropharyngeal/Gastrointestinal • Prominent lymphadenopathy • Recovery followed by permanent immunity Tularemia Clinical Types Clinical presentation based on the route of infection Typhoidal tularemia • Bacteremia- Sepsis • Fever, chills, headache, myalgias, malaise, sore throat, and anorexia. • Likely bioterrorism presentation. Pneumonic tularemia • Entry into lungs via – Aerosols – hematogenous • Severe atypical pneumonia • Likely BT presentation Pathogenesis • Facultative intracellular pathogen • Capsule protects against complement killing • Macrophage uptake – bacterial surface polysaccharides – serum complement – complement C3 receptors • LPS - O antigen – prevents maturation of the phagosome • multiply to high levels in cytosol • Bacterial release via apoptosis Diagnosis • Symptoms & History • Direct staining of clinical specimens with a fluorescein-labeled antibodies. • Serum antibody titers of 1:160 or greater • Culture on cysteine-rich media • Notify Laboratory personnel if you suspect Francisella since it is HIGLY INFECTIOUS Treatment of Tularemia • Prompt removal of ticks and insect repellent can prevent disease. • Antibiotics – Streptomycin is the drug of choice Yersinia Overview: 3 species cause human disease • Yersinia pestis • Yersinia enterocolytica • Yersinia pseudotuberculosis Overview: Plague • Yersinia pestis; a gram-negative bacterium. • Three forms of clinical illness; – Bubonic – Septicemic – Pneumonic • Pneumonic is the only one transmitted through aerosals. Plague: Overview • Natural disease of rodents • Fleas that live on rodents transmit the bacteria to humans, in the bubonic form. • This disease occurs in many areas of the world, including the United States. Plague: Overview • U.S. averages 13 cases/yr (17 in 2006) • Plague is endemic in the desert southwest. • Most cases occur in summer. Microscopic Characteristics • Y. pestis appear as single cells or short chains of plump, gram-negative rods. Microscopic Characteristics Gram stain: – In direct smears, bacterial cells may be inside or outside of leukocytes. – The Gram smear morphology is suggestive but not specific for Y. pestis. Bipolar staining of a plague smear prepared from lymph aspirated from a bubo of plague patient. Microscopic Characteristics • Bipolar staining occurs when using Wayson, or Giemsa stain. CDC Colony Characteristics • Grows well on most standard laboratory media. • Sheep Blood Agar – Gray-white translucent colonies – Pinpoint, graywhite, non-hemolytic at 24 hours Blood agar plate of Yersinia pestis at 48 hours. CDC/Dr. Brodsky Y. pestis: Physiology • Non-motile • Pleomorphic gram-negative bacillus • Urease, and oxidase negative • Facultative anaerobe • Optimal growth at 28o C • Facultative intracellular parasite Public Health Aspects of Plague • Fleas carry Y. pestis in their intestinal tract. • When feeding the fleas regurgitate uncapsulated organisms. • Bacteria re-encapsulate and grow. • Progeny are resistant to intracellular killing Yersinia pestis life-cycle Plague - Clinical types • Bubonic • infected lymph nodes. • Pneumonic (most likely BT presentation) • transmissible by aerosol; deadliest. • Septicemic • blood-borne organisms. Bubonic Plague • Regional lymphadenitis (Buboes) – Inguinal, axillary, or cervical lymph nodes most common – 80% can become septic – 60% mortality if untreated • Cutaneous findings – Possible papule, vesicle, or pustule at inoculation site – Purpuric lesions - late Bubo • swollen inguinal lymph node or bubo. • After the incubation period of 2-7 days, symptoms of the plague appear. Pneumonic Plague • Pneumonic – From aerosol or septicemic spread to lungs. – Person-to-person transmission by respiratory droplet. – 100% mortality untreated. • Pneumonia progresses rapidly to dyspnea, cyanosis. • Death from respiratory collapse/sepsis. Septicemic Plague • Primary or secondary – Secondary from bubonic or pneumonic forms – 100% mortality if untreated • Severe endotoxemia • Systemic inflammatory response syndrome • Shock, Disseminated intravascular coagulopathy (DIC) • Adult Respiratory Distress Syndrome (ARDS) Y. pestis: Virulence Determinants • 3 virulence encoded Plasmids • Virulence is up-regulated at 37°C • Capsule (F1 antigen) Yersinia Outer Proteins (Yops) • 11 different proteins • Antiphagocytic • Inhibit production – proinflammatory cytokines – tumor necrosis factor • Cytotoxin Yops • Targets – dendritic cells – macrophages – Neutrophils – does not target B and T lymphocytes F-1 Antigen • Glycoprotein capsule expressed at 370 C • Not expressed in flea host • Antiphagocytic • Antibodies to F-1 are protective Plasminogen activator (fibrinolysin) and Coagulase • Plasmid encoded proteins • Promote dissemination of organisms from the clot at the bite site • Coagulase is produced at 280 C but not at 320 C. Diagnosis • Examination of Bubo aspirate, blood, sputum • stained for bipolar staining • Fluorescent-antibody • Culture (hazardous) Plague Treatment • Y. pestis is susceptible to a variety of antibiotics. – streptomycin, tetracycline, and doxycycline • Peumonic plague is contageous and isolation is recommended. Clinical Case • 30 year old man from Colorado, went to a hospital emergency department with a 3day history of fever, nausea, vomiting, and right inguinal lymphadenopathy. • Patient was not a hunter nor had he been in the woods recently but he did have dogs. • He was discharged home without treatment. • Three days later, the man returned and was hospitalized with sepsis and bilateral pulmonary infiltrates. • One of the patient's dogs had serologic evidence of past Y. pestis infection. • Cultures of blood and a lymph node aspirate.