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Questions and Answers

What is a significant consequence of Chlamydia trachomatis infection?

It can cause brain lesions.

It causes gastrointestinal ulcers.

It results in respiratory syndromes.

It can lead to blindness due to trachoma. (correct)

Which form of anthrax has the highest mortality rate?

Gastrointestinal anthrax

Zoonotic anthrax

Cutaneous anthrax

Inhalational (pulmonary) anthrax (correct)

What type of bacteria does Chlamydia belong to?

Facultative anaerobes

Free-living bacteria

Obligate parasites (correct)

Nitrogen-fixing bacteria

What might occur as a result of Chlamydia infection in the female reproductive system?

Permanent damage to fallopian tubes Signup and view all the answers

Which of the following diseases is associated with Bacillus anthracis?

Anthrax Signup and view all the answers

What type of bacteria are characterized by their complex life cycle involving elementary and reticulate bodies?

Chlamydia Signup and view all the answers

What was one of the earliest documented uses of biological weapons?

Plague-ridden bodies used by Tartar army against Kaffa Signup and view all the answers

Which organism is NOT associated with the phylum Chlamydia?

Bacillus anthracis Signup and view all the answers

What type of toxin is produced by Vibrio cholerae?

Enterotoxin Signup and view all the answers

Which of the following characteristics describes endotoxins?

They can cause fever Signup and view all the answers

What is the primary impact of the infection caused by B. pertussis on the lungs?

Impaired ability to clear mucus Signup and view all the answers

What can result from an infection of B. pertussis in newborns?

Severe illness and a risk of death Signup and view all the answers

How does H. pylori affect most individuals who have it?

It typically leads to gastritis Signup and view all the answers

What is a significant concern regarding the vaccination for whooping cough?

Uptake of the vaccine is critical to its effectiveness Signup and view all the answers

What type of organism is Pseudomonas and its relatives classified as in terms of their morphology?

Rods or curved rods Signup and view all the answers

What best describes the relationship of endotoxins to Gram-negative bacteria?

They are part of the outer membrane Signup and view all the answers

What is the difference between pathogenicity and virulence?

Pathogenicity is the ability to cause disease, and virulence is the extent of that ability. Signup and view all the answers

What type of toxin is produced by Corynebacterium diphtheriae?

A-B toxin Signup and view all the answers

Which microorganism is known for using actin to move from one host cell to another?

Listeria Signup and view all the answers

What percentage of hospital patients are affected by nosocomial infections?

5–15% Signup and view all the answers

What term describes the presence of a toxin in the host's blood?

Toxemia Signup and view all the answers

Which of the following describes biofilms?

A community of microorganisms adhering to a surface. Signup and view all the answers

Which bacteria is associated with producing superantigens?

Streptococcus pyogenes Signup and view all the answers

What is the main characteristic of vehicle transmission?

Transmission via inanimate reservoirs like food and water. Signup and view all the answers

Signup and view all the answers

Study Notes

Agricultural Microbiology - MICR20010 Assessments

Practical reports are due on time; avoid plagiarism (15%)
Practical online MCQ exam on Friday, November 22nd, 2-3 pm (15%)
Final MCQ exam in RDS on December 12th, 9:30 am (70%)

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 (including fungi)
Lecture 16: Microbiology in the Food Industry (fermentations)
Lecture 17: The Nitrogen Cycle

Transmission of Disease

Direct contact transmission: Examples demonstrating physical contact transmission
Droplet transmission: The transmission of disease through aerosols produced by coughing, sneezing, or talking.
Vehicle transmission: Diseases transmitted through an inanimate reservoir like food, water, or air.

Nosocomial Infections

Acquired during a hospital stay
Affects patients (number not specified)
Transmission can be prevented by using gloves, masks, and face shields

Mechanisms of Pathogenicity

Pathogenicity: The ability to cause disease
Virulence: The extent of pathogenicity

Mechanisms of Pathogenicity (detailed)

Portals of Entry:
- Mucous membranes
- Respiratory tract
- Gastrointestinal tract
- Genitourinary tract
- Conjunctiva
- Skin
- Parenteral route
Penetration or Evasion of Host Defenses:
- Capsules
- Cell wall components
- Enzymes
- Antigenic variation
- Invasins
- Intracellular growth
Damage to Host Cells:
- Siderophores
- Direct damage
- Toxins
- Exotoxins
- Endotoxins
- Lysogenic conversion
- Cytopathic effects
Portals of Exit: The same mechanisms as the portals of entry

Infection and Adherence

Adhesins/ligands bind to receptors on host cells:
- Fimbriae (Escherichia coli)
- M protein (Streptococcus)
Formation of biofilms

Penetration into the Host Cell Cytoskeleton

Invasins (proteins that facilitate entry):
- Salmonella, altering host actin to enter a host cell
- Listeria, using actin to move between cells

Direct Damage by Bacteria

Disrupt host cell function
Produce waste products
Toxins
- Toxin: Substance contributing to pathogenicity
- Toxigenicity: The ability to produce a toxin
- Toxemia: Presence of toxin in the host's blood

Exotoxins (types)

A table with examples of bacteria and their corresponding exotoxins
- 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: Gram-negative outer membrane
Chemistry: Lipid A
Fever? Yes
Neutralized by Antitoxin? No
LD50: Relatively large

The Stages of a Disease

A graph illustrating the stages of a disease
- Incubation period (no signs or symptoms)
- Prodromal period (mild symptoms)
- Period of illness (severe symptoms)
- Period of decline (symptoms lessen)
- Period of convalescence (recovery)

Bacterial Diseases (Chronic vs Acute)

Information about various bacterial diseases and their classification as chronic or acute

Pseudomonas and the Pseudomonads

Colony Morphology: Rod-shaped or curved rods with polar flagellae
Burkholderia, Pseudomonas, etc.
Challenge for patients with Cystic Fibrosis

The Human Lung

Diagram of the human lung, showing the various sections from the nasal passage through to the alveoli and relevant detail

Developing Chronic Infection

Intermittent colonization first
Followed by a persistent chronic infection
Accompanied by a higher degree of inflammation

B. Pertussis - An Acute Infection

Gram-negative rod-shaped bacterium
Lung infection, but not opportunistic
Highly contagious due to coughing spasms
Uses virulence factors to cause disease

Whooping Cough (Symptoms and Treatment)

Symptoms:
- Paroxysmal cough (“whoop”)
- Rib fractures, hernias, loss of consciousness
Severity for newborns: High risk of death
Incubation and catarrhal stages, followed by uncontrollable fits
Prevention/Treatment: Vaccination with pertussis toxin, is relatively successful. Vaccination uptake is critical

H. pylori - Commensal or Pathogen?

Gram-negative spiral organism
Resides in the human stomach/duodenum
Often asymptomatic, but can cause gastritis in most individuals
- More serious diseases: Duodenal Ulcers, MALT Lymphoma, Gastric Cancer
Brief History: Discovered in 1982, it was initially thought stomach was sterile, and ulcers were due to stress.
Pathology of Infection:
- Can colonize the human gastric mucosa
- Causes gastritis (in most individuals colonized), which can be asymptomatic
- Can develop into more serious diseases like duodenal ulcers and gastric cancers (A class 1 carcinogen?)
Disease Progression: A schematic visualizes the progression of disease: Normal, Acute, Chronic; various types of gastritis, Intestinal metaplasia, and Gastric cancer stages.

Chlamydia – An Intracellular Pathogen

15-25 year olds are at the highest risk..
Cases are rising steadily
Obligate intracellular parasite (needs host cell for survival)
- C. trachomatis (STD and trachoma)
- C. psittaci (Psittacosis)
- C. pneumoniae (Respiratory syndromes)
Limited metabolic pathways
Lack some genes (ftsZ)
Presence of eukaryotic-like genes
Life Cycle: Elementary and Reticulate bodies

Bacterial Diseases of the Eye

Chlamydia trachomatis causes trachoma
Leading cause of blindness worldwide
Scars from infection abrade the cornea and cause blindness

Anthrax

Bacillus anthracis, with endospores
Endospores enter through minor wounds, 20% mortality
Gastrointestinal Anthrax. Ingestion of undercooked or contaminated food, 50% fatality
Inhalational Anthrax. Inhaling endospores, 100% mortality

Biological Weapons

Historical examples of biological weapons use (plagues, flea bombs)

Biological Weapons (Bacteria and Viruses)

Table listing types of bacteria and viruses that have been used in biological weapons

Typhoid Fever

Salmonella typhi causing typhoid fever
Bacteria spreads throughout body in phagocytes
1-3% of those recovered become chronic carriers
200,000 fatalities
Important aspect of asymptomatic infection

Pathogenic Fungi and Viruses (Next Topic)

Next topic in the course

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