Definitions Microbial pathogenesis--process of causing disease Colonization-presence of microbes at site of body Does not imply tissue damage or disease symptoms Does imply invasion of site and multiplication BIOL 533 Lecture one
Lecture One BIOL 533 2 Definitions • Microbial pathogenesis—process of causing disease • Colonization—presence of microbes at site of body – Does not imply tissue damage or disease symptoms – Does imply invasion of site and multiplication
Characteristics of Parasitism Encounter: agent meets host Entry: agent enters host Spread: agent spreads Multiplication: agent multiplies Damage: agent, host response or both cause damage Outcome: agent or host wins or coexist BIOL 533 Lecture One
Lecture One BIOL 533 3 Characteristics of Parasitism • Encounter: agent meets host • Entry: agent enters host • Spread: agent spreads • Multiplication: agent multiplies • Damage: agent, host response, or both cause damage • Outcome: agent or host wins, or coexist
Encounter In utero Do not normally come in contact with organisms Protection of fetal membranes Do not normally come in contact with organisms from mother Normally only present sporadically Exceptions: sexual diseases virus causes rubella BIOL 533 Lecture One
Lecture One BIOL 533 4 Encounter • In utero – Do not normally come in contact with organisms • Protection of fetal membranes • Do not normally come in contact with organisms from mother – Normally only present sporadically – Exceptions: sexual diseases, virus causes, rubella
Encounter At moment of birth Come in contact with organisms present in vaginal canal and on skin Previously, antibodies passed from mother to fetus Defenses are good for a period of time, then they wane BIOL 533 Lecture one
Lecture One BIOL 533 5 Encounter • At moment of birth – Come in contact with organisms present in vaginal canal and on skin • Previously, antibodies passed from mother to fetus • Defenses are good for a period of time, then they wane
Encounter Challenge between man and microbe wages many times during lifetime Most disappear rapidly Some become part of normal flora Only a few cause disease BIOL 533 Lecture one
Lecture One BIOL 533 6 Encounter • Challenge between man and microbe wages many times during lifetime – Most disappear rapidly – Some become part of normal flora – Only a few cause disease
Later Encounters EXogenous: encountered in environment Endogenous: encountered in or on body Organisms present on skin can cause disease when they go into deeper tissues BIOL 533 Lecture One
Lecture One BIOL 533 7 Later Encounters • Exogenous: encountered in environment • Endogenous: encountered in or on body – Organisms present on skin can cause disease when they go into deeper tissues
Later Encounters Example Staphylococcus aureus enters cut and forms boil In this case encounter took place long before disease (at time skin was colonized) Encounter is not always sharply demarcated BIOL 533 Lecture one
Lecture One BIOL 533 8 Later Encounters • Example: – Staphylococcus aureus enters cut and forms boil – In this case, encounter took place long before disease (at time skin was colonized) • Encounter is not always sharply demarcated
Normal flora What constitutes normal flora? Some people possess StreptocoCCus pyogenes in their throat for long periods, but rarely contract disease Opportunistic pathogen existence(carrier state) 95% of people never have this bacterium, and when they do, they get sick BIOL 533 Lecture One
Lecture One BIOL 533 9 Normal Flora • What constitutes normal flora? – Some people possess Streptococcus pyogenes in their throat for long periods, but rarely contract disease • Opportunistic pathogen existence (carrier state) – 95% of people never have this bacterium, and when they do, they get sick
Normal flora defined Constitutes normal fora if definition is any organism present that is not causing disease Not normal fora if used to mean organisms present in majority of population BIOL 533 10 Lecture One
Lecture One BIOL 533 10 Normal Flora Defined • Constitutes normal flora if definition is “any organism present that is not causing disease” • Not normal flora if used to mean organisms present in majority of population
Host-Parasite Interaction Exposure to virulent agents does not always lead to disease Typhus and Black Plague epidemics only half of population became sick, even hough most likely exposed BIOL 533 11 Lecture one
Lecture One BIOL 533 11 Host-Parasite Interaction • Exposure to virulent agents does not always lead to disease – Typhus and Black Plague epidemics: only half of population became sick, even though most likely exposed