Agricultural Microbiology Past Paper PDF

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 22nd (15%) Sample MCQs to appear next week. Final MCQ exam in RDS on 12t...

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 22nd (15%) Sample MCQs to appear next week. Final MCQ exam in RDS on 12th December 9.30 – Confirm on exam timetable (70%) Sample MCQs to appear next week.  MICR20010 - remaining lectures Lecture 10 – Microorganisms and Disease Lecture 11 – The Immune System Lecture 12 - Pathogenic Bacteria Lecture 13 – Pathogenic Fungi and Viruses Lecture 14 – Antibiotic Resistant Microorganisms Lecture 15 – Microbiology in the Food Industry – The Fungi Lecture 16 – Microbiology in the Food Industry - Fermentations Lecture 17 – The Nitrogen Cycle 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 A-B toxin diphtheriae Membrane-disrupting Streptococcus pyogenes 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 Gram Relation to Microbe Outer membrane Chemistry 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