Bacterial Pathogenicity

Question 1

Gram +ve vs Gram -ve bacteria

Answer 1

Question 2

Acid-Fast Bacteria

Answer 2

Gram +ve but will not show a result on stain due to waxy cell wall

e.g. mycobacteria

Question 3

Types of Bacteria that interact with body

Answer 3

Symbionts (Lactobacilli) (can make it difficult for other bacteria to grow, can also produce nutrients like vit B12 in animals)

Commensals (Dont provide harm but don’t benefit either) (e.coli, Neisseria species)

Opportunistic pathogens

Primary pathogens (Mycobacteria, Botulinum, Cholerae)

Accidental pathogens (Neisseria meningitidis; commensal bacteria that can go into blood and cause harm)

Question 4

Opportunistic Pathogens

Answer 4

Pathogens that cause disease in individuals with intact immune systems

Susceptible include:

• Congenital coniditions (CF)
• Acquired conditions (AIDS)
• Immunosupressed (medication)
• Surgical procedures (splenectomy)
• Antibiotic treatment

Question 5

Clostridum Difficile

Answer 5

Commensal bacteria that lives in balance with other bacteria that can become opportunistic; e.g. when patients are given antibiotics and gut bacteria are killed so bacterium can rapidly divide

Question 6

Primary Pathogens

Answer 6

Pathogens capable of establishing infection and causing disease in healthy individuals

Tend to produce pathology that favours survival/dissemination of bacterium

• Toxins that kill/impair leukocytes
• Pathogenesis like coughs that disseminate pathogen (TB)

Question 7

Accidental Pathogens

Answer 7

Neisserium Meningitidis (Kissing virus)

Most neisseria live harmlessly on mucous membranes but become harmful when crossing certain barriers (e.g. entering blood)

Question 8

Zoonotic/Non-zoonotic Pathogens

Answer 8

Zoonotic - Pathogens that infect animals and transfer to humans
(e.g. Campylobacter jejuni - found in raw chicken mear)

Non-zoonotic pathogens - Human specific pathogens (e.g. Neisseria)

Question 9

Do bacteria tend to have single or multi-factorial natures of bacterial pathogenesis

Answer 9

They tend to have a multi-factorial nature of bacterial pathogenesis

Exceptions tend to rely on a single toxin

Question 10

Exo- vs Endo- toxins

Answer 10

Exotoxins - Proteins that disrupt infectee activity

Endotoxins - Lipopolysaccharides that come from vesicles of bacterial cell walls that prompt an immune response

Question 11

Adhesins/Invasins

Answer 11

Pili or Surface Proteins

Question 12

Bacteria with Flagella

Answer 12

Campylobacter jejuni

Vibrio cholera

Question 13

Consequences of bacterial adherence

Answer 13

Prevents pathogens from being lost from host

Causing cytoskeletal changes in host cells that may allow invasion; breaking intracellular junctions

Induction of cytokines which causes inflammation

Question 14

Survival Factors of bacteria

Answer 14

Complement-evading proteins (tricking immune system)
Capsules (protein [S-layers] or polysaccharide) that protect bacteria from environment

Nutrient scavenging system
- Production of siderophore-binding proteins that have high iron affinity

Question 15

Bacterial Biofilms

Answer 15

Bacteria going together to form monolayers then microcolonies and eventually biofilms that have an exopolymer matrix and can be difficult to treat/penetrate

Question 16

Secretion of virulence factors

Answer 16

Methods by bacteria to secrete proteins from the cytosol to the external environment in gram negative bacteria

Haemolysin secreted simply (Type I)
Salmonella (Type III, gets through bacterial cytosol all the way to body cell)

Question 17

Quorum sensing

Answer 17

Means for bacteria to detect environment

Production and release of small molecule; if not picked back up then bacterium assumes it is alone from other bacteria

When there are enough bacteria, ‘molecule’ concentrations reach a threshold where it is detected by luxR protein which can turn on virulence factors and coordinate responses