Relationships 2

Question 1

What is entry?

Answer 1

Initial step in the infectious process

Question 2

What is adhesion?

Answer 2

Adherence to host cells through specific interactions between molecules on the pathogen and molecules on these host cells

Question 3

What are the microbial adhesion factors?

Answer 3

Bacterial- bacterial adhesions
-capsule, fimbrae, pili

Viral- viral adhesion

Viral capsid, viral membrane envelope

Question 4

What is the function of fimbrae/pili?

Answer 4

Helps bacterial cells adhere to surfaces

F pili/sex pili enables conjugation/ dna transfer

Question 5

What are the functions of viral caspid or membrand envelope adhesins?

Answer 5

Helps with adherence to specific proteins, glycoproteins or carbohydrate residues on the host cells surface

Virulence factors with similar functions to bacterial ashesins which facilitate adhesion to host cells

Question 6

What natural environmen5 has microorganisms attached?

Answer 6

Rocks (in a stream) In roots of plants

Question 7

What might Microorganisms attach to in medical environments?

Answer 7

• dental plaque leading to dental caries and gum disease
• Prosthetic heart valves leading to infective endocarditis, intracardiac abscess
• joint prosthesis leading to prosthetic joint infections
• internal catheters leading to catheter related infections
• medical device implants leading to blood stream infections

Question 8

What might microorganisms attach to in the industrial environment?

Answer 8

Food and beverage industries leading to food safety problems

Water processing plants leading to water quality issues

Question 9

Describe biofilm formation

Answer 9

Planktonic

1. Attachment to surface
2. Formation of mono layer and production of matrix
3. Microcolony formation, multi-layer
4. Mature biofilm, with characteristic “mushroom” formed of polysaccharide

Question 10

What is tissue tropism?

Answer 10

Phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens.

Organ and tissue tropism reflects the ability of a given pathogen to infect a specific organ or a set of organs

Question 11

What is colonization?

Answer 11

The process of infection continues with colonization, with or without damage to host tissue

Question 12

What are the outcomes of colonization?

Answer 12

Commensalism- human microbiome, acquisition starting at birth

Infection- these microorganismmay be from exogenous or endogenous sources and have the potential to cause damage to host tissues

Question 13

What are the conditions of colonization?

Answer 13

1. Environments

2nutrient acquisition

Question 14

What environmental factors contribute to colonization?

Answer 14

• pH( h pylori colonizers the stomach ph2-4)
• moisture (corynebacterium colonizers skin)
• temperature
• oxygen content

Question 15

What factors of nutrient acquisition contribute to colonization?

Answer 15

Iron

• host cells
  
  • transferrin andlactoferrin compete for iron acquisition
• pathogens
  
  • siderphores
  • breakdown of iron containing compounds

e. g. N meningitis is
- lactoferrin and transferrin receptors
- hemoglobinreceptors

Question 16

What determines occurrence if disease?

Answer 16

Host, environment, and infectious agent

Question 17

Give examples of agents

Answer 17

Viral/bacterial/ fungi/ reservoirs/ transmission route

Question 18

What factors about host contribute to disease occurrence

Answer 18

Age, sex, immune status, genetic predispo, comorbidites

Question 19

What factors of environment contribute to disease occurrence?

Answer 19

Tropical or temperate countries, sanitation levels, population density, socioeconomic status, vector exposure

Question 20

Contrast infection vs disease

Answer 20

STI DONT EQUAL STD

infection- any situation where a microorganism gains entry, becomes established and is growing in a host, whether or not the host is yet harmed

Disease: growth of microorganism, invading pathogen or commensal results in host damage and production of specific signs

Question 21

What are the bacterial virulence factors?

Answer 21

1. Toxins.
2. Flagella
3. Glycocalyx
4. Bacterial enzymes

Question 22

What are toxins?

Answer 22

Bacterial proteins encoded by the bacterial chromosomal genes or extrachromosomal genes (plasmids, phages)

Question 23

What are endotoxins?

Answer 23

Bacterial toxins secreted from the cells, which bind to specific cell receptors or structures causing a specific action on host cells or tissues

Site of action: neurotoxin, enterotoxin, cytotoxin

Question 24

Give 2 examples of neurotoxins and there purpose

Answer 24

Clostridium botulinum and Clostrudium tetani

Botulinum toxin(Botox) in low concentrations is used for cosmetic and medical procedures

Before the advent of the DTP/. DTaP/ diphtheria and tetanus toxoids(DT), tetanus incidence rates= mortality rates

Question 25

Give an example of an entertoxin and how it works

Answer 25

Entertoxin: cholera toxin Enterotoxins are exotoxins B sub unit binds to ganglioside receptor of epithelial cell A subunit gets inside cell to activate G-protein and activate Adenylyl cyclase pathway Causes release of water, sodium and chloride ions

Question 26

What are endotoxins?

Answer 26

Toxic component of bacteria outer membranes Lipopolysaccharide of gram negative bacteria. Usually has a general effect on host cells and tissues causing symptoms of inflammation and fever The lipid component of endotoxins, lipid A, is responsible for the toxic properties of the LPS molecule

Question 27

Give examples of endotox7ns

Answer 27

Salmonella spp: LPS—> gastroenteritis (food poisoning) N. Meningitidis—> meningococcal meningitis or septicemia

Question 28

Describe flagella as a bacterial virulence factor

Answer 28

Long, thin protrusions from the body Function: - bacterial motility - bacterial adhesion

Question 29

Describe glycocalyx (capsule/slime layer) as a bacterial virulence factor

Answer 29

Coating outside the cell wall of both gram positive and gram negative bacterial cells Usually consists of polysaccharide but can also ne composed of other materials; glycoprotein etc. Function- enhances pathogenicity by preventing phagocytosis by host immune cells

Question 30

Describe bacterial enzymes as bacterial virulence factors

Answer 30

Bacterial proteins which can participate in catalytic reactions. These reactions may be helpful in bacterial cell invasion, host cell evasion and in some cases laboratory identification. Invasins: Hyaluronidase Streptokinase Staphylokinase Hemolysins Catalase

Question 31

What is antigenic variation (discuss as a viral virulence factor)

Answer 31

Occurs mostly in certain types of enveloped viruses Antigenic drift- a result of point mutations causing slight changes in surface glycoproteins Antigenic shift- a major change in surface glycoproteins due to gene assortment E.g. influenza virus - orthomyxovirudae family - single stranded negative sense RNA genome - segmented genome(7-8)