Professional pathogens T4 L3

1. large communities of bacteria 

2. very few cause diseases 

1. when organism invades body 

2. replicates

3. damages host 

1. organism lies on us but doesnt cause infection 

1. organism evades immune defences of hsot to cause infection 

mutual benefit

unequal benefit

1. amlost always cause disease

1. only cause disease in immunocompromised people  

1. fundamental properties of organism

2. severity / harmfullness 

1. probability that an organism is causing disease when its isolated from a patient

1. organisms virulence 

2. where it is: blood/urine= sterile 

stool, throat= not usually sterile 

3.immune state of patient  

1. burns

2. trauma 

3. neutropenia= low neutrophil count 

4. venous catheters 

5. T cell deficiences 

6. HIV

7.steroids

8. diabetes

9. alcohol

10. splenic dysfunction  

1. commensal bacteria, anteior nares 

2. highly adapted

3. like living in nose 

4. golden colonies on agar

5.gram positive cocci in clusters  

6. 20-60% carry it

1. polysaccharide coat, inert

2. hides from immune system 

3. adhesins allow them to stick to different body tissues 

1. distinguish s. aureus from less virulent staphylococci eg s. epidermis or more virulent strains  

1. s. aureus is coagulase positive 

2. s. epidermis negative 

1. pore forming toxins

2.lyse host cells

3. panton-valentine leukocidin  - blows up neutrophils 

1. proteases

2. cause skin to fall off

1.  stimulate massive t cell activation 

2. ingestion- vomitting 

only present on a proprotion of strains 

1. polysaccharide capsule 

2. thin

3.specific antibodies to capsular antigens required  

s. aureus skin infections 

1. 

1. adherence to nasal mucosa by adhesins 

2. ability to onvade tissues through cytotoxins and enzymes

3. ability to evade immune systemusing protein A and capsule

4.ability to replicate and disseminate   

1. innate immune system sensitive to LPS :

evolution happened tis way to deal with bites and wounds 

early recognition of infection

2. LPS interacts with toll like receptors esp TLR4  , distinguish foreign cells 

monocytes: type of white blood cell, high amount indicates some sort of abnormality 

endothelium: surface that lines inside of blood vessels and lymphatic vessels- squamous 

3. results in activation of 

inflammatory pathways 

coagulation and clotting pathways 

changes in endothelial integrity 

GRAM NEGATIVE BACTERIA IN BLOOD-> ENDOTOXIN IN BLOOD 

1. componenent of exteror cell wall

2. LPS 

1. make cell wall with lipoteichoic acid 

2. gram + dont have endotoxins

3.  stimulate immune responses like LPS

4. different toll like receptors 

1. part of innate immune system 

2. recognise microbes 

1. cannot control blood flow in area

2. blood clot 

3. meningococcal septicaemia 

1. specific adhesins for respiratory mucosa

2.pneumolysin :

binds to host cell membanes cholesterol

forms pores and lyses ciliated cells

lyses host phagolytic cells

3. secrete IgA protease : breaks down secreted immunoglobulin A, prevents mucosal clearance

4. capsule: polysaccharide prevents complement mediated phagocytosis : specific recognition 

specific antobies requred for capsule 

> 100 capsule types 

1. generally infectious or neoplastic 

1.