Chapter 14 Flashcards
_____ and ____ membranes are physical barriers to infection
Skin and Mucous
-May supply foundation for microbial ecosystem
Humans are usually _____ in utero
Sterile
-soon after birth microbial populations begin to establish
Normal microbiota
- Resident flora
- transient flora
Isolated colonies in specific body regions. List regions
Nose,Throat, Large intestine, Mouth, Skin, Vagina, Urethra
Factors that influence distribution
- nutrient availability
- salinity
- oxygen availability
- host defenses
- mechanical factors
The dominant type of organism my change with _____ and ______
age and situation
Normal flora play a role in defenses
- Protection from colonization by pathogens
- microbial antagonism
Microbial antagonism
- competitive exclusion
- bacteriocins
Symbiotic relationships form between microbes and host
- Relationships may change depending on state of hose and attributes of microbes
- Mutualism
- Commonsalism
- Parasitism
Mutualism
++
Intestinal bacteria
Probiotics
Commonsalism
+ neutral
Flora on skin and conjunctiva
Parasitism
+-
Pathogens
Pathogenicity
State of host resistance usually determines extent of infection
- primary infection
- secondary infection (typically opportunistic)
- Sub-clinical (inapparent) infection
Distribution of Pathogens
Local infection
Systemic (generalized) infection
Systemic infection
Septicemia can result from
- Bacteremia
- Toxemia
- Viremia
Many people are carriers of pathogens. Why are they less affected or not at all?
.
Predisposing factors
gender genetic background climate and weather inadequate nutrition age habits and lifestyle chemotherapy emotional disturbances
Characteristics of infectious disease
communicable
-contagious
-often reflects ID50
non-communicable disease
Robert Koch demonstrated that specific microbes caused specific diseases
Experimented with grazing animals infected with anthrax
Koch’s postulates
- Same pathogen must be present in each case of disease
- Pathogen is isolated from diseased hose and grown in pure culture
- Pure culture must cause disease when inoculated into healthy animal
- Pathogen must be re-isolated from inoculated animal
Exceptions to Koch’s postulates
- Some bacteria have unique culture requirements
- some diseases are caused by multiple pathogens (polymicrobial diseases [Mixed infections])
- Ethical considerations
States of an Infectious disease
Incubation Prodromal period Illness Decline Convalescance
In order to cause disease pathogen must follow a series of steps
Gain entrance to host Adherence Colonization Avoid hose defenses Cause host damage
Adherence
critical step
binding of adhesins to host receptors is highly specific
Virulence factors
capsules
incomplete phagocytosis
fimbrae
components of cell wall
