Chapter 14 Flashcards
(25 cards)
_____ 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
