C1 Flashcards
Factors of pathogenicity
- Ability pathogen to invade host
- Ability pathogen to multiply in host
- Ability pathogen to avoid host defense
- Number of infectious organism enter the body
Host microbe relationships
- Symbiosis: live together
- Mutualism
- Commensalism
- Parasitism
Normal flora obtained nutrient from
Waste substances secreted by hosts in skin & mucous membrane
Types of normal flora
- Resident
- Transient
- Oppurtunist
Explain resident flora
Always present on / in human body
Explain transient flora
Present only under certain conditions where resident flora found
Explain opportunist
Not normally cause disease but do when opportunity arise
Conditions that create opportunist flora
- Breakdown host immune
- Microbe introduced to unusual body sites
- Normal flora disturbed
Define virulence
Intensity of diseases caused by pathogens
Virulence measured by
- ID50
- LD50
Define ID
Estimated no of organism/virus particles required to produce infection in 50% of normal adult exposed by given route
Define LD
Amount of material given all at once which cause death of 50% of tested animals
Example of vector
- Antropod: fleas, tick
- Inanimate: fomites
Types of vector
- Biological: infected
- Mechanical: not infected
What is Koch postulate proposed by Robert Koch
- Microbes must be regularly isolated from cases of disease
- Grown in pure culture in vitro
- When inoculated into susceptible animal, disease must show
- Identical microbes must be isolated from animal
Molecular Kosch Postulates
- Virulence trait associated more in pathogenic strains
- When virulence gene inactivated, pathogenicity reduce or loss
- Wildtype gene reintroduce, pathogenicity restores
- Gene express at some point during infection
- Antibody directed against gene product should protect host
Types of infectious diseases
- Communicable: spread to one another
- Non communicable: not spread
Non communicable diseases normally occurs by
- Individual own microflora
- Organisms from outside cause disease when introduced into body
- Poisoning following exposure ingestion of preformed toxin
Occurrence of disease in population
- Endemic: present continually in population
- Epidemic: higher than normal incidence in population
- Pandemic: epidemic spread worldwide
- Sporadic: occur at random, isolated cases
Source of infectious diseases
- Endogenous
- Congenital
- Exogenous
- Health care associated infection
Explain endogenous infection
- Source of pathogen is host
- Organism moves to another site in body
Explain congenital infection
- Infection in fetus
- Can occur during passage through birth canal
Explain exogenous
- Organism from external environment
- Various routes of transfer
Explain health care associated infection
- Endogenous or exogenous
Factor influencing susceptibility to infectious disease
- Age
- Host factor
- Life style of host
- Gender
- Genetic determinants of host
Types of host factor that influence susceptibility to infectious diseases
- Stress
- Diet
- Health status
Stages of disease
- Incubation
- Prodromal
- Invasive
- Decline
- Convalescence
Explain incubation period
- Time between infections & appearance of sign and symptoms
- Length depend on pathogen & virulence
Explain prodromal period
- After incubation period
- Early mild symptoms & sign of disease
- Not all diseases have prodromal
Explain invasive phase
- Period of illness
- Sign & symptoms apparent
- Host doing best to fight off disease
- Ability to overcome determine the recovery or death
Explain decline phase
- Infection under control
- Host begins to recover
- If cannot completely get rid - result in chronic or latent infections
Explain convalescence period
- Host repair damage brought by infection
- Body return to normal health
