R.O Lecture 8&9

Question 1

Virulence Factors

Answer 1

Specialised structures or characteristics that improve the ability of an organism to cause infection and disease.

Question 2

Adherence

Answer 2

Attachment to host cell’s surfaces; important tool for initiation of infection

Question 3

Adhesins

Answer 3

• proteins/glycoproteins that bind to complementary surface receptors (usually glyoproteins/sugars) on host cells.
• Found on surfaces of bacterial attachment pili or glycocalyx
• Adhere to membranes of specific cell types

Question 4

Is aderence alone sufficient to cause infection?

Answer 4

• No, adherence alone is not sufficient to cause infection.
• Microbes must be able to colonise the tissue surface or penetrate it

Question 5

Types of identified adhesions and their targets

Answer 5

Refer to slide 3

Question 6

Action of Hyaluronidase in bacterial invasion

Answer 6

• Enzyme that digests hyaluronic acid (a glue-like substance that holds cells together in some tissues)
• Produced by some pneumococci and streptococci species
• Enables passage through the epithelium to deeper tissues

Question 7

Coagulase

Answer 7

• Enzyme that causes blood clotting; can aid infection by some bacterial species like Staphylococcus aureus; protects them from immune defenses

Question 8

Streptokinase

Answer 8

Enzyme that dissolves blood clots; allows bacteria trapped within a clot to free themselves and spread the infection

Question 9

Can organisms such as Mycobacterium tuberculosis and Neisseria gonorrhoeae survive within host cells?

Answer 9

Organisms such as Mycobacterium tuberculosis and Neisseria gonorrhoeaecan survive within host cells –escape destruction and are transported to other tissues

Question 10

Toxin

Answer 10

A toxin is any substance that is poisonous to other organisms

Question 11

Toxigenicity

Answer 11

• The capacity of microbes to produce toxins.
• Can produce fever, cardiovascular disturbances, diarrhoea, destroy blood cells/vessels, disrupt the nervous system, inhibit protein synthesis, damage cell membranes etc.

Question 12

Endotoxins

Answer 12

• Part of the outer membrane of Gram-negative bacteria; released into host tissue when bacteria die or divide.
• Consist of Lipid A portion of Lipopolysaccharide (LPS) complexes
• Relatively weak unless released in large doses
• Non-specific effects: Fever, sudden drop in blood pressure (endotoxic shock)
• Produced by species including Salmonella typhi, Neisseria meningitidis

Question 13

Exotoxins

Answer 13

• Soluble substances produced by Gram-positive and Gram-negative bacteria that are secretedinto the host tissues
• Produced by species of Clostridium, Bacillus, Staphylococcus, Streptococcus etc.
• Most are polypeptides; some are enzymes.
• Most genes for exotoxins are carried on plasmids/phages

Question 14

Cytotoxins

Answer 14

Kill host cells/inhibit their functions

Question 15

Neurotoxins

Answer 15

Interfere with nerve impulse transmission

Question 16

Enterotoxins

Answer 16

• Affect cells lining the GI tract
• Includes cholera toxin (Vibrio cholerae), heat-labile enterotoxin (E. coli) and Staphylococcal enterotoxin (S. aureus)
• Can cause symptoms by attaching to GI cell membranes and causing them to release fluids, disturbing the electrolyte balance and affecting muscle contractions
• Diarrhea, vomiting

Question 17

Hemolysins

Answer 17

Lyse red blood cells; produced by Strepto-and Staphylococci; release iron.

• α-hemolysin - Partially break down hemoglobin
• β-hemolysin - Completelybreak down hemoglobin

Question 18

Botulisim neurotoxin (BoNT)

Answer 18

• Botulism neurotoxin (BoNT) blocks acetylcholine (neurotransmitter) release from excitatory neurons at neuromuscular junctions, preventing muscle contraction (botulism).

Question 19

Tetanus neurotoxin (TeNT)

Answer 19

blocks acetylcholine (neurotransmitter) release from inhibitory neurons, preventing muscle relaxation (tetanus).

Question 20

Bacterial Meningitis

Answer 20

• Inflammation of the meninges (membranes covering CNS)
• Causes necrosis, clogging of blood vessels, increased intracranial pressure, decreased CSF flow, impaired CNS function.
• Toxins (pneumolysin) produced by S. pneumonia contribute to disease (cytotoxins)
• Most cases are acute but some can be chronic

Question 21

Hansen’s disease (leprosy)

Answer 21

• Caused by Mycobacterium leprae.
• Disfiguring chronic disease.

Question 22

Tetanus

Answer 22

• Severe muscle spasms; caused by Clostridium tetani.
• Tetanus toxin (neurotoxin): affects central nervous system, blocking neurotransmitter release from inhibitory neurons leading to lock jaw, muscle rigidity and muscular spasms.

Question 23

Botulism

Answer 23

• Botulism-severe muscle relaxation; caused by Clostridium botulinum.
• Neurotoxin blocks the release of acetylcholine at the junction between neurons and muscle cells; thusmuscle stimulation does not occur

Question 24

What are the three forms of botulism?

Answer 24

• Foodborne (intoxication)
• Infant
• Wound (infection and intoxication)

Question 25

Erysipelas

Answer 25

lesions form on skin and spread. Caused by haemolytic streptococci

Question 26

Impetigo

Answer 26

* Highly contagious and caused by staphylococci and/or streptococci. * Treated with penicillin. * Almost exclusive to children

Question 27

Acne

Answer 27

* Affects 80% of teenagers and many adults. * Propionibacteriumacnes responsible for severe cases * Feeds on sebum produced by sebaceous glands in skin (overproduction can be hormone stimulated)

Question 28

Burn infections

Answer 28

* Severe burns can remove much of the body’s protective barrier * Pseudomonas aeruginosais prime cause of infections * Treatment difficulties such as antibiotic access issues (topical treatments or debridement) and antimicrobial resistance | Refer to slide 16

Question 29

Explain the function of lysozyme in tears

Answer 29

* Antimicrobial effect of tears on M. luteus * Tears also contain other antimicrobial agents. e.g. lipocalin, lactoferrin, sIgA

Question 30

Ophthalmia neonatorum

Answer 30

* Bacterial eye disease * Conjunctivitis of the newborn * Caused by Neisseria gonorrhoeaeand Chlamydia trachomatis (birth canal) * Can cause inflammation of the cornea (keratitis)

Question 31

Bacterial conjuctivitis (pink eye)

Answer 31

* Extremely contagious * Caused by S. aureus, Neisseria gonorrhoeaeand Pseudomonas spp. * Causes inflammation of the conjunctiva

Question 32

Trachoma

Answer 32

* Bactieral eye Disease * Caused by Chlamydia trachomatis * Infection and destruction of conjuctivia; cause of preventable blindness

Question 33

Gas gangrene

Answer 33

* In body regions where oxygen concentration is low, spores germinate, multiply, and produce toxins (alpha toxin: cytotoxin) and enzymes. * As the organisms divide they ferment muscle carbohydrates and produce hydrogen gas. * These gas bubbles distort and destroy tissue. * Produces blackening of tissue

Question 34

Upper respiratory tract infections

Answer 34

* Pharyngitis - sore throat - S.pyrogenes * Laryngitis - infection of the larynx, loss of voice * Epiglottitis - infection of the epiglottis * Sinusitis, bronchitis, tonsillitis ## Footnote Last 3 - S.pneumoniae and H.influenzae

Question 35

Name diseases of the lower respiratory tract

Answer 35

* whopping cough (pertussis) * Pneumonia * Tuberculosis

Question 36

Whooping cough (pertussis)

Answer 36

* Main causative agent is Bordetellapertussis (aerobic, encapsulated, Gram negative coccobacillus) * Inhaled organisms colonise the cilia lining the respiratory tract; produces endotoxin, exotoxins (cytotoxins: pertussis toxin, tracheal toxin) and hemagglutinins (adhesins) * Disease causes mucus and masses of bacteria to fill the airway leading to violent coughing

Question 37

Pneumonia

Answer 37

* Inflammation of lung tissue (children and older adults have higher risk) * Can be caused by bacteria, viruses, fungi, inorganic sources * Main causative agent is Streptococcus pneumoniae (pneumococcus); can cause fibrin deposits leading to blockage (consolidation) of air spaces and pleurisy * Disease causes violent chills, fever, chest pain, cough, and sputum-containing blood.

Question 38

Tuberculosis

Answer 38

* Caused by bacteria from the Mycobacterium tuberculosis complex; aerobic, rod-shaped, long doubling time; replicate inside phagocytes (e.g. neutrophils, macrophages); elicit acute inflammatory response and can produce lesions * Prior to 1900, one-third of adults died of TB before reaching old age * BCG vaccine (M. bovis strain) * Treatment of latent infection with extended course of antibiotics