MICR20010C.pptx

MICR20010 Agricultural Microbiology Dr. Tadhg Ó Cróinín MICR20010 – Assessments • Remember to get your practical reports submitted on time, watch plagiarism. (15%) • Practical online MCQ exam on 2-3pm Friday Nov 24th, More info to follow (15%) • Final MCQ exam in RDS on 15th December 16.30 – Conf...

MICR20010 Agricultural Microbiology Dr. Tadhg Ó Cróinín MICR20010 – Assessments • Remember to get your practical reports submitted on time, watch plagiarism. (15%) • Practical online MCQ exam on 2-3pm Friday Nov 24th, More info to follow (15%) • Final MCQ exam in RDS on 15th December 16.30 – Confirm on exam MICR20010 - remaining lectures Representative Normal Microbiota Figure 14.1 Commercial as well as Health Implications! Transmission of Disease Figure 14.6a, d Vehicle Transmission • Transmission by an inanimate reservoir (food, water, air) Figure 14.7b Vectors Figures 14.8, 12.30 Nosocomial Infections • Are acquired as a result of a hospital stay • Affect 5–15% of all hospital patients Figure 14.6b Mechanisms of Pathogenicity • Pathogenicity: The ability to cause disease • Virulence: The extent of pathogenicity Mechanisms of Pathogenicity Figure 15.9 Infection and Adherence • Adhesins/ligands bind to receptors on host cells – Fimbriae: Escherichia coli – M protein: Streptococcus pyogenes • Form biofilms Adherence Figure 15.1 Penetration into the Host Cell Cytoskeleton Invasins Salmonella alters host actin to enter a host cell Listeria Uses actin to move from one cell to the next Figure 15.2 Direct Damage by bacteria • Disrupt host cell function • Produce waste products • Toxins – Toxin: Substance that contributes to pathogenicity – Toxigenicity: Ability to produce a toxin – Toxemia: Presence of toxin in the host's blood Figure 15.4 Exotoxin type A-B toxin, Membrane disrupting toxin, Superantigens Exotoxin Corynebacterium diphtheriae A-B toxin Streptococcus pyogenes Membrane-disrupting erythrogenic toxin Clostridium botulinum A-B toxin; neurotoxin C. tetani A-B toxin; neurotoxin Vibrio cholerae A-B toxin; enterotoxin Staphylococcus aureus Superantigen Endotoxins Source Relation to Microbe Chemistry Gram Outer membrane Lipid A Fever? Yes Neutralized by Antitoxin? No LD50 Relatively large Figure 15.4b The Stages of a Disease Figure 14.5 Bacterial Diseases Chronic vs Acute Pseudomonas and the Pseudomonads • Colony morphology • Rods or curved rods with polar flagellae • Burkholderia, Pseudomonas etc. • A particular challenge for those with Cystic Fibrosis The Human Lung Developing Chronic Infection • Intermittent colonization first • Followed by a persistent chronic infection • Accompanied by a higher degree of Inflammation. B. Pertussis – An acute Infection • Also a gram-ve rod shaped organism. • Thus a similar cell envelope to that of P. aeruginosa. • Also infects the lungs but this time not opportunistic… • Highly contagious due to coughing spasms. • Uses an array of virulence factors to cause disease. Whooping Cough What is Happening • The bacterial infection is affecting the ability of the lungs to clear mucus. • An inability of the cilia to clear the mucus sends the host into a fit of coughing. • This in itself allows the bacteria to be spread rapidly by aerosol. Huge array of virulence factors! The Symptoms • Paroxysmal cough, inspiratory “whoop” • Rib fractures, hernias, loss of conciousness • Infection in newborns can be particularly severe and result in death in approx 1% • 7-10 days incubation period followed by catarrhal stage, then two weeks later uncontrollable fits set in. Treatment/Prevention? • Vaccination with pertussis toxin relatively successful. • An effective vaccine… but….. • Uptake of vaccine critical. H. pylori– Commensal or Pathogen? • Also a gram-ve organism but this time spiral shaped • Thus a similar cell envelope to that of the other Gram-negative organisms. • Only known to reside in the human stomach/duodenum. • Gastritis in most individuals • More serious disease A Brief History • Discovered in 1982 • Before this stomach thought to be sterile • Ulcers thought to be stress related. • A paradigm shift in the treatment Pathology of Infection • The only known bacteria to colonize the human gastric mucosa. • Gastritis induced in all individuals colonized but typically asymptomatic. • Some can develop into more serious disease such as – Duodenal Ulcers, MALT Lymphoma, Gastric Cancer • A class 1 carcinogen? Disease Progression Chlamydia – An intracellular pathogen • 15-25 are most at risk. • Steady rise in Chlamydia cases Phylum 5 - Chlamydia Phylum 5 : Chlamydia • Organisms are obligate parasites – C. trachomatis - STD and trachoma – C. psittaci – Psittacosis – C. pneumoniae – Respiratory syndromes • Clearly limited metabolic pathways • Lack of some genes (ftsZ) • Presence of some eukaryotic-like genes Life Cycle of Chlamydia • Elementary and Riticulate bodies • Thus a more complex life cycle. • Key is the obligate intracellular life cycle. Different Niches – Different Outcomes • The male and female reproductive organs contain very different environments. • Also different epithelial surface cell molecules. • This has a big effect on the progression of disease. • Can cause permanent damage to fallopian tubes and sterility in Bacterial Diseases of the Eye • Chlamydia trachomatis – Causes trachoma – Leading cause of blindness worldwide – Infection causes permanent scarring; scars abrade the cornea leading to blindness Anthrax Bacillus anthracis • Endospores enter through minor cut – 20% mortality • Gastrointestinal anthrax – Ingestion of undercooked, contaminated food – 50% mortality • Inhalational (pulmonary) anthrax – Inhalation of endospores – 100% mortality Biological Weapons • 1346: Plague-ridden bodies used by Tartar army against Kaffa • 1937: Plague-carrying flea bombs used in the Sino-Japanese War • 1979: Explosion of B. anthracis weapons plant in the Soviet Union • 1984: S. enterica used against the people of The Dalles • 1996: S. dysenteriae used to contaminate food • 2001: B. anthracis distributed in the United States Biological Weapons Bacteria Viruses Bacillus anthracis “Eradicated” polio and measles Brucella spp. Encephalitis viruses Chlamydophila psittaci Hermorrhagic fever viruses Clostridium botulinum toxin Influenza A (1918 strain) Coxiella burnetii Monkeypox Francisella tularensis Nipah virus Rickettsia prowazekii Smallpox Shigella spp. Yellow fever Vibrio cholerae Yersinia pestis Typhoid Fever • Salmonella typhi • Bacteria spread throughout body in phagocytes • 1–3% of recovered patients become chronic carriers • 200,000 deaths/yr The Importanc e of asymptom atic Infection Next on MICR20010 Pathogenic Fungi and Viruses Dr. Tadhg Ó Cróinín