Chapter 14 - Infections, Infectious Diseases, and Epidemiology Flashcards
Symbiosis
- to live together
- symbiotic relationships w countless microbes
types of symbiosis
1 mutualism
2 commensalism
3 parasitism
Mutualism
benefits both organisms
es) bacteria in human colon
Commensalism
organism 1: benefits,
organism 2: neither benefits nor is harmed
ex) staphylococcus
Parasitism
organism 1 benefits,
organism 2 harmed
ex) TB in human lung
Normal Microbiota in hosts
+++no star+++
aka normal flora + indigenous microbiota
-organisms that colonize the body’s surface w/o normally causing disease
2 types of normal microbiota
+++no star+++
1 resident microbiota (always present)
2 transient microbiota (temp present)
resident bacteria of lower digestive tract
mostly strict anaerobes but has some facultative anaerobes present as well
highest diversity of resident microbiota
higher and lower digestive tract
uterus
no microbiota present; sterile.
Transient Microbiota
- remains in body for short period
- found in same regions as resident microbiota
- handwashing get rid of transient/pathogenic flora
- CANNOT PERSIST IN BODY
factors that makes transient microbiota unable to persist in body
- competition fr other microbes (normal flora is always reestablished)
- elimination by body’s defense cells
- chem or physical change in the body
Acquisition of normal microbiota
- dvlpt in womb is AXENIC
- microbiota begin to develop during birthing process
- MUCH OF ONE’S RESIDENT MICROBIOTA IS ESTABLISHED DURING THE FIRST FEW MONTHS OF LIFE
Axenic
free of microbes
when is one’s resident microbiota established?
during the first few months of life after birth.
Zoonoses
diseases naturally spread from animal host to humans
various routes of acquiring zoonoses
1 direct contact w animal or its waste (rabies)
2 eating animals (salmonellosis)
3 bloodsucking arthropods (yellow fever, west nile virus)
*humans are usually a dead-end host to zoonotic pathogens
Nonliving Reservoirs
- soil, water, + foods can be reservoirs of infection
- presence of microbes due to contamination by feces/urine
- FORMITES
formites
inanimate objects involved in the indirect contact transmission of pathogens
reservoirs of infectious diseases
- sites where pathogens are maintained as a source of infection
- most pathogens CANT survive for long outside of their host
3 types of reservoirs
1 animal reservoir
2 human carrier
3 nonliving reservoirs
contamination
presence of microbes in or on the body
infection
-invasion of the host by a pathogen
when organism evades body’s external defenses, multiplies, and becomes established in the body
portals of entry
sites thru which pathogens enter the body
-skin, mucous membranes, placenta, parenteral route
portals of entry:
Mucous Membrane
- mucous membr lines the body cavities that are open to the environment
- provides moist, warm environment hospitable to pathogens
- respiratory that is the most common site of entry
- gastrointestinal tract may be route of entry (must survive acidic pH)
most common site of portal entry
respiratory tract is the most common site of entry
-through nose/mouth
Disease
results if the invading pathogen alters normal body functions
-aka morbidity
Manifestations of Disease
1 symptoms
2 signs
3 syndromes
4 asymptomatic or subclinical
symptoms
subjective characteristics of disease felt only by the patient
(ex. aches)
signs
objective manifestations of disease observed or measured by others (ex. fever is above a certain temp)
syndromes
symptoms and signs that characterize a disease or abnormal conditions
ex. immunocompromised symptoms of AIDS
asymptomatic or subclinical
infections lack symptoms but may still have signs of infections
signs vs symptoms
signs are objective/measured and symptoms are subjective
Virulence Factors of Infectious Agents
- virulence (degree of pathogenicity
- virulence factors contribute to virulence
pathogenicity
ability of microbes to cause disease
Virulence Factors
1 adhesion factors (pili) 2 biofilms 3 extracellular enzymes 4 toxins 5 antiphagocytic factors (capsule)
toxin (virulence factor)
- chem that harms tissues or trigger host immune responses that cause damage
- Toxemia
Toxemia
refers to toxins in the bloodstream that are carried beyond the site of infection
2 types of bacterial toxins
endotoxin
exotoxin
Stages of Infectious Disease
-the disease process occurs after infection
5 stages
5 Stages of Infectious Disease
1 incubation period 2 prodromal period 3 illness 4 decline 5 convalescent
incubation period
- occurs right after initial infection
- no signs/symptoms
- similar to lag phase
prodromal period
- vague, general period
- similar to log phase, # increases and signs/symptoms begin
illness period
-most severe sign/symptoms
decline
-organism declines in number
convalescence
- body is exhausted, more prone to more infection
- no more signs/symptoms
portals of exits
- how pathogens leave the body
- secreted/excreted
transmission of infectious disease
-transmission is from a [reservoir] or [portal of exit] to another host’s [portal of entry]
3 groups of transmission of infectious disease
1 CONTACT (direct, indirect (formite), or droplet (aerosol) 2 VEHICLE (airborne, waterborne, foodborne (fecal-oral) 3 VECTOR (bio or mechanical)
2 measures of frequency of disease
1 Incidence
2 Prevalence
- tracks the occurrences of disease
- used in epidemiology
Incidence
- number of NEW cases of a disease in a given area during a given period of time
- (NEW cases in area/time)
-used in epidemiology to track the occurrences of disease
Prevalence
- number of TOTAL cases of a disease in a given area during a given period of time
- (TOTAL cases in area/time)
-used in epidemiology to track the occurrences of disease
Frequency of Disease
- 2 measures (incidence + prevalence)
- occurrence is also evaluated by frequency and geographic distribution
Endemic
a disease that is constantly present in low numbers in a population
Epidemic
a disease occurring in an unusually high number of individuals in a population at the same time
Pandemic
a worldwide endemic
-a disease occurring in an unusually high number of individuals in the world at the same time
Sporadic
- occurring at irregular intervals or only in a few places
- scattered or isolated
Nosocomial Infections
-acquired after the patient checks into the hospital
3 types of nosocomial infections
1 Exogenous
2 Endogenous
3 Iatrogenic
Exogenous
- type of nosocomial infection
- pathogen acquired from the health care environment
ex) patient in ICU is incubated and tubes + catheters have been contaminated w mersa.
Endogenous
- type of nosocomial infection
- pathogen arises from normal microbiota due to factors w/in the health care settings
ex) catheter causes UTI tract from patient’s own normal flora
Iatrogenic
- type of nosocomial infection
- results fr modern medical procedures
ex) result of an ear replacement surgery that was contaminated
Pathogen
any microbe that causes disease
Opportunistic Pathogen
normal microbiota that cause disease under certain circumstances
Conditions that provide opportunities for OPPORTUNISTIC ORGANISMS to become pathogenic (3)
1 intro of normal microbiota into unusual site in body
2 immune suppression
3 changes in normal microbiota
infectuous disease
invasion
disease
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plasma
buffy coat
WBC + platelet
