Theme 8
Defini&ons
• Pathology - study of disease
• E&ology - study of the cause of the disease
• Pathogenesis - the manner in which the disease develops
• Infec&on - coloniza&on of the body by pathogens
• Disease - infec&on causes an abnormal state in which the body is not func&oning
normally
Rela&onship between normal microbiota and host
• Normal microbiota prevent growth of harmful microorganisms - microbial
antagonism / compe&&ve exclusion
• Prevent growth by compe&ng for nutrients / producing substances harmful to
invading microbes and affect condi&ons such as Ph or O2 levels
• When balance is upset - disease results
• Normal microbiota and host - symbiosis
Types of symbiosis
• Commensalism - one benefits and other is unaffected
• Mutualism - benefits both organisms
• Parasi&sm - one organisms benefits by deriving nutrients at expense of other
• Opportunis&c pathogens - don’t cause disease in their normal habitat in a healthy
person but may do so in a different environment
Koch’s postulates
1. The same pathogen must be present in every case of the disease
2. The pathogen must be isolated from the diseased host and grown in pure culture
3. The pathogen from pure culture must cause the disease when inoculated into a
healthy animal
4. The pathogen must be isolated from the inoculated animal and must be shown to be
the original organism
• Excep&ons - some pathogens can cause several disease condi&ons / some pathogens
cause disease only in humans / some pathogens cannot be cultured / disease
symptoms can be liked to several pathogens
Diseases
• Symptoms - subjec&ve and only felt by person not seen
• Signs - objec&ve changes that can be seen and measured
• Communicable disease - disease in which an infected person transmits and infec&ous
agent to another person who in turn becomes infected
• Contagious diseases - very communicable and capable is spreading easily and rapidly
• Non-communicable disease - not spread
• Incidence - number of people in a Popula&on who develop a disease during a
par&cular &me period
• Prevalence - number of people in a popula&on who develop a disease at a spceificed
&me, regardless of when it first appeared
• Sporadic diseases - only occurs occasionally
• Endemic - constantly present disease in a popula&on
• Epidemic - many people in a Given area acquire a certain disease in a rela&vely short
period
Defini&ons
• Pathology - study of disease
• E&ology - study of the cause of the disease
• Pathogenesis - the manner in which the disease develops
• Infec&on - coloniza&on of the body by pathogens
• Disease - infec&on causes an abnormal state in which the body is not func&oning
normally
Rela&onship between normal microbiota and host
• Normal microbiota prevent growth of harmful microorganisms - microbial
antagonism / compe&&ve exclusion
• Prevent growth by compe&ng for nutrients / producing substances harmful to
invading microbes and affect condi&ons such as Ph or O2 levels
• When balance is upset - disease results
• Normal microbiota and host - symbiosis
Types of symbiosis
• Commensalism - one benefits and other is unaffected
• Mutualism - benefits both organisms
• Parasi&sm - one organisms benefits by deriving nutrients at expense of other
• Opportunis&c pathogens - don’t cause disease in their normal habitat in a healthy
person but may do so in a different environment
Koch’s postulates
1. The same pathogen must be present in every case of the disease
2. The pathogen must be isolated from the diseased host and grown in pure culture
3. The pathogen from pure culture must cause the disease when inoculated into a
healthy animal
4. The pathogen must be isolated from the inoculated animal and must be shown to be
the original organism
• Excep&ons - some pathogens can cause several disease condi&ons / some pathogens
cause disease only in humans / some pathogens cannot be cultured / disease
symptoms can be liked to several pathogens
Diseases
• Symptoms - subjec&ve and only felt by person not seen
• Signs - objec&ve changes that can be seen and measured
• Communicable disease - disease in which an infected person transmits and infec&ous
agent to another person who in turn becomes infected
• Contagious diseases - very communicable and capable is spreading easily and rapidly
• Non-communicable disease - not spread
• Incidence - number of people in a Popula&on who develop a disease during a
par&cular &me period
• Prevalence - number of people in a popula&on who develop a disease at a spceificed
&me, regardless of when it first appeared
• Sporadic diseases - only occurs occasionally
• Endemic - constantly present disease in a popula&on
• Epidemic - many people in a Given area acquire a certain disease in a rela&vely short
period
