Mycobacterium, Helicobacter pylori & Corynebacterium dyphtheria. Stijn van der Veen

Transcription

1 Mycobacterium, Helicobacter pylori & Corynebacterium dyphtheria Stijn van der Veen

2 Mycobacterium Genus consisting of over 190 species Myco means "fungus, given for its filamentous, mold-like growth Mycobacterium tuberculosis Tuberculosis Mycobacterium leprae Leprosy

3 Overview of bacterial infections - Mycobacterium leprae

4 Mycobacterial cell envelope The Mycobacterial cell envelope is waxy. This enables Mycobacteria to survive exposure to: acids alkalis detergents oxidative bursts lysis by immune system many antibiotics 1. Outer lipids 2. Mycolic acid 3. Polysaccharides 4. Peptidoglycan 5. Plasma membrane 6. Lipoarabinomannan (LAM) 7. Phosphatidylinositol mannoside

5 Acid-fast (Mycobacterial) staining procedure Ziehls carbol fuchsin (3 5 min heat) => rinse Acid Alcohol (10 15 sec) Crystal violet (1 min) => rinse => rinse & dry

6 Löwenstein Jensen medium Specific growth medium for Mycobacteria M. tuberculosis appears as brown, granular colonies, with a "buff, rough and tough morphology. The medium must be incubated for several weeks due to the slow growth rate of Mycobacteria Malachite green is added to the medium to inhibit other bacteria

7 Generation/Doubling time Mycobacteria are slow growers and have a very long generation time. Mycobacterium leprae has the longest doubling time of all known bacteria and has never been cultured in the laboratory without a surrogate host. Organism Generation Time Clostridium perfringens min Escherichia coli Staphylococcus aureus min Mycobacterium tuberculosis hrs Mycobacterium leprae 14 days

8 Tuberculosis is a lower respiratory infection The respiratory system is composed of a conducting portion that brings oxygen to the lungs and a respiratory portion that exchanges oxygen and carbon dioxide with the bloodstream. The respiratory system can be divided into URT & LRT. Microbial colonization is generally limited to the URT.

9 Tuberculosis The causative agent Mycobacterium tuberculosis Sign and symptoms Active TB: cough, weight loss, fatigue, fever, night sweats, chills, breathing pain Transmission Respiratory droplets Treatment Antibiotics Prevention and control Preventing exposure to active TB patients, BCG vaccine

10 Tuberculosis is widespread It is estimated that 1/3 of the world population is infected with M. tuberculosis. Typically a lung disease but can also affect other parts of the body. Death from tuberculosis per 100,000 inhabitants in 2004

11 Progress of tuberculosis

12 Anatomy of the tubercle 1. Inhaled Mycobacteria are phagocytozed by alveolar macrophages in the lung 2. Localized inflammatory response attracs more mononuclear cells from neighboring blood vessels 3. A granuloma develops consisting of a central area containing infected macrophages, which is surrounded by foamy macrophages, cells with high lipid content and other immune cells 4. The granuloma matures and the surrounding layer of lymphocytes becomes associated with fibrous collagen 5. When the immune defenses fail, the granuloma decays into a formless mass and the bacteria are released 6. Bacteria are able to spread by aerosols through coughing

13 TB disease progression is complex

14 Tuberculin skin test Growth and identification of M. tuberculosis from sputum samples is a long process due to slow growth Tuberculin skin test is a more rapid method to identify people that have been infected before and show antibody responses to the bacterium Purified protein derivative (PPD) is injected Diameter of induration is read after 2-3 days 5 mm of induration is classified as positive result

15 Mycobacterium tuberculosis vaccine The vaccine against tuberculosis contains a live, attenuated strain of Mycobacterium bovis called BCG. It is recommended for children at high risk for exposure to active tuberculosis in some countries. The effectivity of the vaccine is variable (0-80%). Vaccine has many known side-effects and leaves a scar.

16 Global BCG vaccination policies A. Countries who have adopted universal program of BCG immunization and currently recommend a single dose of BCG. B. Countries who had earlier recommended but currently have ceased booster immunization of BCG. C. Countries promoting repeat vaccination of BCG. D. Countries who do not recommend BCG immunization. E. Countries who had earlier adopted universal program of BCG and currently don't use it. F. Countries in which BCG vaccination status is unknown. Tuberculosis 98 (2016) 149e158

17 BCG efficacy

18 Leprosy (Hansen Disease) The causative agent Mycobacterium leprae Sign and symptoms Disfiguring of skin and bones, loss of pain sensation, loss of facial features Transmission Nasal secretions Treatment Multidrug therapy with dapsone, rifampin and clofazime Prevention and control Avoiding contact where endemic

19 Leprosy In old times called Curse of the Damned. It did not kill, but it also never ended. Leprosy afflicted were often expelled from communities or deported to designated islands for fear of transmission In fact, leprosy is not very infectious and natural immunity is widespread Spinalonga island, near Crete

20 Mycobacterium virulence factors

21 Mycolic acids Are β-hydroxy C fatty acids with long α-alkyl side-chain of C in length Important for resistance against chemical injury and dehydration Resist phagocytic digestions

22 Sulfatides 3-O-sulfogalactosylceramide Prevent phagocyte activation and phagosome-lysosome fusion

23 Trehalose di-mycolate (cord factor) Inhibits phagocyte chemotaxis, activation, phagosomelysosome fusion and digestion

24 Lipoarabinomannan (LAM) Inhibits phagocyte activation and digestion within the phagocyte

25 Corynebacterium Coryne means "clubshaped, given for clublike appearance during some stages of growth Corynebacterium diphteria Diphteria

26 Overview of bacterial infections - Corynebacterium diphteria

27 Identification of Corynebacterium Loffler medium is used to preferentially grow C. diphteria Tellurite agar is selective and differential because tellurite inhibits growth of many bacteria and tellurite reduction is visible giving grey/black colonies Another characteristic are polar metachromatic granules of RNA and polymetaphosphate that can be identified with stains

28 Diphtheria The causative agent Corynebacterium diphtheriae Sign and symptoms Sore throat and low-grade fever, formation of pseudomembrane on tonsils or pharynx Transmission Respiratory droplets Treatment Penicillin, erythromycin Prevention and control Vaccination with DTaP

29 Diphtheria toxin This toxin inhibits protein synthesis in eukaryotic cells and can cause death. Particularly harmful to heart and central nervous system. The lethal dose is as low as 100 to 150 ng/kg

30 Pseudo-membrane Peuso-membrane is composed of Fibrin Dead epithelial cells Bacteria Neutrophils Pseudo-membrane can exfoliate easily and block the airways Hypoxia Suffocation

31 Diphtheria vaccine Contains the toxoid (formaldehyde-treated exotoxin). Immunization against diphtheria is indicated for every child and dependent on the specific country is given in three doses at 2, 4, and 6 months of age, with boosters given 1 year later and at intervals thereafter.

32 Helicobacter pylori Helicobacter pylori has a helical morphology, also indicated as spirilia Spirilla have a helical shape and fairly rigid bodies.

33 Overview of bacterial infections

34 Urea breath test The urea breath test is most commonly used for detection of Helicobacter pylori H. pylori produces an enzyme called urease Urease breaks urea down into ammonia and carbon dioxide A tablet containing minimally radioactive urea ( 13 C) is swallowed The urease enzyme converts it into radioactive carbon dioxide The amount of exhaled radioactive carbon dioxide is measured This indicates the presence of H. pylori in the stomach.

35 Gastric / peptic ulcers The causative agent Helicobacter pylori Sign and symptoms Abdominal pain, nausea, vomiting Toxin involved Cytotoxin Transmission Fecal-oral? Treatment Combination of antibiotics with proton pump inhibitors Prevention and control Good hygiene

36 Helicobacter pylori infection H. pylori penetrates the stomach mucous layer and attaches to the stomach wall It secretes the enzyme Urease, which generates ammonia that neutralizes the acid in the vicinity of the infection Ammonia and cytotoxin cause destruction of the mucous secreting cells and exposes the underlying connective tissue An ulcer appears, which can further develop into cancer H. pylori infection gives a 10-20% lifetime risk of developing peptic ulcers and 1-2% of stomach cancer

37 Helicobacter pylori colonization

38 H. pylori incidence More than 50% of the world population is infected with H. pylori Up to 15% of people infected with H. pylori experience symptoms or complications Prevalence of H. pylori infection New stomach cancer cases annually

39 Discovery of Ulcers as infectious disease In 1982, 2 Australian gastroenterologists, Marshall and Warren, identified bacterial cells living in the stomach lining of over 100 patients who had ulcers. Initially they had trouble cultivating the bacteria under normal conditions and so where not taken seriously They speculated that ulceration was the result of the infection, but nobody was convinced by their research A frustrated Marshall drank a dilute solution of the bacterium and said: If my theory is correct, I should get an ulcer

40 Discovery of Ulcers as infectious disease And guess what, 14 days later he had a the clear signs of stomach inflammation and an infection In 1993, they published in the New England Journal of Medicine about their study showing that 48 of 52 patients with peptic ulcers were cured in 6 weeks after 12 days of antibiotics In all it took 10 years for the medical community to agree with their findings but In 2005, they won the Nobel price for their discovery!!

41 H. pylori virulence factors

42 Lipopolysaccharide (LPS) & Flagella LPS and flagella of H. pylori subvert immune recognition

43 Type IV secretion system Secretion of effectors such as proteins and peptidoglycan into the host cell cytosol

44 Cytotoxin associated gene A - CagA Effector protein of the type IV secretion system Causes uncontrolled host cell growth and inhibition of apoptosis Not present in all strains

45 Vacuolating toxin A - VacA Induces vacuolation in epithelial cells Disruption of epithelial hunctions Release of cytochrome c from mitochondria, leading to apoptosis Stimulates proinflamatory response and neutrophil migration into the mucosa

46 Outer membrane protein OiPA Phosphorylation by OipA regulates various epithelial cell signaling pathways OipA induces inflammation and actin dynamics OiPA is an adhesin and is involved in the attachment of H. pylori to gastric epithelial cells

47 Next lecture Anaerobic bacteria and more