Agricultural Microbiology - MICR20010 Quiz

Agricultural Microbiology - MICR20010

• Course code is MICR20010
• Course name is Agricultural Microbiology
• Lecturer is Dr. Tadhg Ó Cróinín

Assessments

• Practical reports are due on time, avoiding plagiarism (15%)
• Practical online MCQ exam on Friday, November 22nd, 2-3pm (15%) Sample MCQs available next week
• Final MCQ exam on December 12th, 9.30am in RDS (70%) Sample MCQs available next week

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 - Fungi
• Lecture 16: Microbiology in the Food Industry - Fermentations
• Lecture 17: The Nitrogen Cycle

Commercial and Health Implications

• Guinness recalled non-alcoholic stout in the UK due to safety concerns
• Dunnes Stores and Lidl recalled chicken products due to bacteria contamination

Transmission of Disease

• Direct contact transmission: illustrated with a picture of people interacting.
• Droplet transmission: illustrated with a picture of a person coughing or sneezing.

Vehicle Transmission

• Transmission through an inanimate reservoir like food, water, or air.
• Picture of someone preparing food is shown.

Vectors

• Illustrated with pictures of a fly near food and a mosquito on a person's arm.

Nosocomial Infections

• Infections acquired during a hospital stay.
• Affect 5-15% of patients.
• Preventing direct contact transmission (gloves, masks, face shields).

Mechanisms of Pathogenicity

• Pathogenicity: ability to cause disease.
• Virulence: extent of pathogenicity.
• Shows different types of bacteria (spherical, rod-shaped, spiral).

Mechanisms of Pathogenicity (detailed)

• Portals of entry: Mucous membranes, respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin, and parenteral route.
• Penetration/Evasion of host defenses: capsules, cell wall components, enzymes, antigenic variations, invasins, intracellular growth.
• Damage to host cells: siderophores, direct damage, toxins (exotoxins, endotoxins), lysogenic conversion, cytopathic effects.
• Portals of exit: generally the same as portals of entry.
• Adherence: Adhesins/ligands bind to receptors on host cells (e.g., fimbriae, M protein).
• Formation of biofilms.
• 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)

Infection and Adherence

• Adhesins/ligands bind to receptors on host cells (e.g., Fimbriae, M protein)
• Form biofilms

Direct Damage by Bacteria

• Disrupt host cell function
• Produce waste products
• Toxins: substance contributing to pathogenicity
• Toxigenicity: ability to produce a toxin
• Toxemia: presence of toxin in the host's blood (exotoxin and endotoxin)

Exotoxin types

• Table listing exotoxins, their type, and the bacteria they are produced by (A-B toxin, Membrane disrupting toxins, Superantigens)

Endotoxins

• Source: Gram-negative bacteria
• Relation to Microbe: Outer membrane
• Chemistry: Lipid A
• Fever?: Yes
• Neutralized by Antitoxin?: No
• LD50: Relatively large

Stages of a Disease

• Incubation period (no signs or symptoms)
• Prodromal period (mild signs or symptoms)
• Illness period (most severe signs and symptoms)
• Decline period (signs and symptoms)
• Convalescence period

Bacterial Diseases

• Chronic vs Acute

Pseudomonas and Pseudomonads

• Colony morphology: rods or curved rods with polar flagellae
• Burkholderia, Pseudomonas, etc.
• A particular challenge for those with Cystic Fibrosis

The Human Lung

• Diagram showing the different zones and structures (conducting zone, respiratory zone)

Developing Chronic Infection

• Intermittent colonization followed by a persistent chronic infection.
• Accompanied by higher degree of inflammation.

B. Pertussis - An Acute Infection

• Gram-ve rod-shaped organism.
• Similar cell envelope to P. aeruginosa, but not opportunistic.
• Highly contagious due to coughing spasms.
• Uses virulence factors to cause disease.

Whooping Cough

• Symptoms include paroxysmal cough (inspiratory "whoop"), rib fractures, hernias, loss of consciousness.
• 7-10 day incubation period followed by a catarrhal stage, then uncontrollable fits after two weeks.
• High severity in newborns (approx. 1% fatality).

Treatment/Prevention

• Vaccination with pertussis toxin is relatively successful.
• Effective vaccine, but vaccine uptake is critical.

H. pylori - Commensal or Pathogen?

• Gram-negative, spiral-shaped organism.
• Similar cell envelope to other Gram-negative organisms.
• Only known to reside in the human stomach/duodenum.
• Gastritis in most individuals.
• More serious disease in others

A Brief History

• Discovered in 1982.
• Stomach previously thought to be sterile, with ulcers attributed to stress.
• Paradigm shift in the treatment of gastric disease.

Pathology of Infection

• Only bacteria known to colonize the human gastric mucosa.
• Induce gastritis in all colonized individuals (typically asymptomatic).
• Some can develop into more serious diseases (Duodenal Ulcers, MALT Lymphoma, Gastric Cancer).
• Class 1 carcinogen?

Disease Progression

• Diagram illustrating the progression from normal gastric mucosa to various stages of infection and disease (acute H. pylori infection, chronic infection, antral-predominant etc.).

Chlamydia - An Intracellular Pathogen

• 15-25 year olds most at risk.
• Steady rise in Chlamydia cases.

Phylum 5 - Chlamydia

• Obligate parasites
• Different species cause different syndromes (C. trachomatis - STD, trachoma; C. psittaci - psittacosis; C. pneumoniae - respiratory syndromes).
• Limited metabolic pathways, lack of some genes (ftsZ).
• Presence of some eukaryotic-like genes.

Life Cycle of Chlamydia

• Elementary and riticulate bodies.
• More complex life cycle.
• Key is obligate intracellular life cycle.

Different Niches - Different Outcomes

• Male and female reproductive organs have very different environments.
• Differences in epithelial surface cell molecules affect disease progression.
• Can cause permanent damage to fallopian tubes and sterility in women.

Bacterial Diseases of the Eye

• Chlamydia trachomatis causes trachoma.
• Leading cause of blindness worldwide due to permanent scarring of the cornea.

Anthrax

• Bacillus anthracis endospores can enter through cuts.
• 20% mortality in cut infections
• Gastrointestinal anthrax: ingestion of contaminated food (50% mortality)
• Inhalation anthrax: inhalation of endospores (100% mortality).

Biological Weapons

• Historical examples: plague-ridden bodies, flea-borne plague, anthrax weapons plants, contamination of food, etc.

Biological Weapons (detail)

• Table listing various bacterial and viral biological weapon agents and details

Typhoid Fever

• Bacteria (Salmonella typhi) spreads throughout the body in phagocytes.
• 1-3% of recovered patients become chronic carriers.
• 200,000 deaths
• Importance of asymptomatic infection

Next on MICR20010 - Pathogenic Fungi and Viruses

• Course code is MICR20010
• Pathogenic Fungi and Viruses
• Lecturer is Dr. Tadhg Ó Cróinín

Test your knowledge on Agricultural Microbiology with this quiz, covering topics such as microorganisms, diseases, and their health implications. Engage with questions related to key lectures and practical assessments in the course. Ideal for students seeking to reinforce their understanding and prepare for upcoming exams.