FHD - commensalism and pathogenesis

what is an apparent infection

an infection that produces symptoms

what is a latent infection

an infection that is inactive or dormant

what are silent or subclinical infections

active infections that do not produce noticeable symptoms

what are the six points of the chain of infection

portal of entry, susceptible host, causative agent, reservoir, portal of exit, mode of transmission

what is meant by the reservoir

the place where the agent supplies, grows, and multiplies

what are the six transmission routes

horizontal, vertical, zoonotic, nosocomial, iatrogenic, germ-line

what is horizontal transmission

transmission between members of the same species

what is vertical transmission

transmission from parent to offspring

what is nosocomial transmission

when an infection is acquired in a hospital or healthcare setting

what is iatrogenic transmission

transmission via medical treatment or procedure

what is germ-line transmission

transmission via the genome

what are the six transmission modes

contact, droplet, airborne, ingestion, inoculation, transplacental

what is meant by the inoculation transmission mode

transmission through sharp injury or bites

what is meant by transplacental transmission

microbes travel through the placenta from the mother to the foetus 

what type of transmission can droplet transmission lead to 

transmission via fromites 

what are fromites

surface viruses

which can travel further, airborne transmissions, or droplet transmissions 

airborne transmissions 

which transmission is easier to control, airborne or droplet

droplet transmission 

what are two ways in which the chain of infection can be broken at the reservoir stage

via occupational health, and control of environmental disease

what is meant by occupational health

immunisation and regular checkups 

how can the chain of infection be broken at the portal of exit

via the practice of aseptic techniques, correct waste disposal, appropriate use of mask and gloves

how can the chain of infection be broken at the mode of transmission stage (in terms of contact precautions)

single patient per room, PPE use and removal, disinfection of equipment

how can the chain of infection be broken at the mode of transmission stage (in terms of droplet precautions)

single patient per room, limit patient movement out of room, use of surgical masks

how can the chain of infection be broken at the mode of transmission stage (in terms of airborne precautions)

negative pressure, N95/P2 masks, limit patient movement outside of room

what are the four types of infections

acute, chronic, primary, latent

what is meant by an acute infection

an infection with sudden, rapid onset, where the host response and viral infection constantly change until resolution 

what is meant by a chronic infection 

a continued infection that exists beyond the time where the immune system should have cleared it

what is meant by a primary infection

the initial infection of the host by a pathogen

what is meant by a latent infection

a persistent infection that does not have any symptoms after the primary infection

what is a latent infection caused by

DNA viruses or retroviruses which may induce cellular transformation 

what is meant by pathogenicity

the capacity of an organism to cause disease

what is meant by virulence

the degree of pathogenicity caused by an organism

what is meant by commensal

an organism the receives benefit from the host without causing harm

how does a commensal act in immunocompromised patients

more akin to a pathogen 

what are the five different virulence mechanisms

surface proteins, surface factors, exotoxins, adhesins, cytotoxins and enzymes

what is the function of surface proteins in virulence

to promote the colonisation of the host

what is the function of surface factors in virulence

to inhibit phagocytic engulfment 

what are two examples of surface factors

protein A and capsule

what is the function of exotoxins in virulence 

they damage the host cell tissues and promote symptoms of disease

what is the function of adhesins in virulence

they allow for adherence to nasal mucosa

what is the function of cytotoxins and enzymes in virulence

they allow for the invasion of tissue

what are LPS

lipopolysaccharides

where are LPS found

on the outer membrane of gram negative bacteria

what acts as a PAMP (pathogen associated molecular pattern) on gram negative bacteria

lipopolysaccharides/ LPS

what does LPS interact with 

toll-like receptors on monocyte and endothelial cells 

why do gram negative infections cause people to get incredibly sick

they have endotoxins. so cause systemic activation of the immune system

which type of bacteria do not have endotoxin

gram positive bacteria

how do gram positive bacteria stimulate immune response 

via their cell wall components, Lipoteichoic acid and peptidoglycans