Microbio Ch. 13

Microbiology ch. 13 "microbe-human interactions - infection, disease and epidemiology".

microbes that engage in mutual or commensal associations with humans (i.e. commensals) =

Normal Resident microbiota

microbe that has penetrated the host defenses, invaded sterile tissue, and multiplied =

infection

damage to host, any deviation from health =

disease

disease-causing microbe =

pathogen

uterus and its contents are normally _____ and remain so until just before birth

sterile

breaking of fetal membrane exposes the infant; all subsequent handling and feeding will continue to introduce what will be the normal flora =

initial colonization of the newborn

old age or youth, genetic or acquired defects in immunity, surgery, organic diseases, immunosuppressive drugs, physical and mental stress, or other infections are all examples of factors that =

increase host susceptibility to infection

characteristic route a microbe follows to enter the tissues and the body =

portal of entry

originate from a source outside the body =

exogenous agents

already exist on or in the body (normal microbiota) =

endogenous agents

portals of entry include =

skin, GI tract, respiratory tract, urogenital tract, transplacental

syphilis, toxoplasmosis, other diseases (hep B, AIDS, chlamydia), rubella, cytomegalovirus and herpes simplex virus are described as =

STORCH, pathogens that can infect during pregnancy

minimum number of microbes required for an infection to proceed =

infectious dose (ID)

Microbes with _____ IDs have _____ virulence

small, greater

lack of ID results in =

no infection

traits used to invade and establish themselves in the host

virulence factors

what do virulence factors determine?

degree of tissue damage that occurs, severity of disease caused

initial response of host defenses comes from _____, which engulf and destroy pathogens

phagocytes

antiphagocytic factors include =

leukocidins, slime layer or capsule, ability to survive phagocytosis

an enzyme that is secreted by a cell and functions outside that cell =

exoenzymes (extracellular enzymes)

capacity to produce toxins at the site of multiplication =

toxigenicity

toxin that is not secreted but is released after the cell is damaged =

endotoxin

toxin molecule secreted by a living bacterial cell into the infected tissue =

exotoxin

characteristics of exotoxins include =

strong specificity for target cell, hemolysins, active-binding toxins

effects of exotoxins include =

damage to target organs, dysfunction occurs

effects of endotoxins include =

general physiological effects like fever, malaise, aches, shock

exotoxins are toxic in _____ doses, whereas endotoxins are toxic in _____ doses

low, high

exotoxins are specific to _____, while endotoxins are _____

cell type, systemic

exotoxins stimulate _____ in the immune response

antitoxins

in contrast to endotoxin, exotoxins usually _____ stimulate fever

dont

endotoxins contain all gram-_____ bacteria

negative

how do a-b toxins work?

B component binds to the cell, A component inhibits protein synthesis

the time from initial contact with the infectious agent to the appearance of first symptoms, agent is multiplying but damage is insufficient to cause symptoms, can be several hours to several years =

incubation period

stage of infection characterized by vague feelings of discomfort, nonspecific complaints =

prodromal stage

stage of infection characterized by agent multiplying at high levels, becoming well established, more specific signs and symptoms =

period of invasion

stage of infection characterized by the person beginning to respond to the infection, symptoms decline =

convalescent period

type of infection in which microbes enter the body and remain confined to a specific tissue =

localized infection

type of infection in which infection spreads to several sites and tissue fluids enter bloodstream =

systemic infection

type of infection in which the infectious agent breaks loose from a local infection and is carried to other tissues =

focal infection

infection in which several microbes grow simultaneously at the infection site =

mixed infection, polymicrobial

initial infection is described as =

primary infection

another infection caused by a different microbe is described as =

secondary infection

infection that comes on rapidly with severe but short-lived effects =

acute infection

infection that progresses and persists over a long period of time =

chronic infection

period of invasion is the state of infection where the person most _____

symptomatic

earliest symptoms of a disease as a result of immune system activation =

fever, pain, soreness, swelling

signs of inflammation include =

edema, granulomas and abscesses, lymphadenitis

signs of infection in the blood =

leukocytosis, leukopenia, septicemia

increase in white blood cells =

leukocytosis

decrease in white blood cells =

leukopenia

microorganisms are multiplying in the blood and present in large numbers =

septicemia

although infected, the host does not show any signs of disease =

asymptomatic

portals of exit include =

respiratory, skin cells, fecal, urogenital tract, removal of blood

infection in which the pathogen is not active or causing disease =

latency

person with a latent infection who sheds the infectious agent =

chronic carrier

long term or permanent damage to tissues or organs =

sequelae

primary habitat of a pathogen in the natural world =

reservoir

reservoirs of pathogens include =

humans, animals, soil, water, plants

individual object from which an infection is actually acquired (door knob, roomate, baby etc) =

source

an individual who inconspicuously shelters a pathogen and spreads it to others, may or may not have experienced disease due to the microbe =

carrier

contaminated healthcare provider picks up pathogens and transfers them to other patients =

passive carrier

an inanimate object that transports a pathogen =

fomite

individual who spreads the infectious agent during the incubation period =

incubation carrier

individual who is recuperating without symptoms =

convalescent carrier

individual who shelters the infectious agent for a long period =

chronic carrier

individual who passes the infectious agent without showing symptoms =

asymptomatic carrier

when an infected host can transmit the infectious agent to another host and establish infection in that host =

communicable disease

infectious disease does not arise through transmission from host to host. occurs primarily when a compromised person is invaded by their own flora, or from contact with an organism in natural, non-living reservoir =

non-communicable disease

transmission by physical contact or fine aerosol droplets =

direct contact

transmission through agent passing from infected host to intermediate conveyor and then to another host =

indirect contact

transmission through inanimate material, food, water, biological products, fomites =

vehicle

transmission through droplet nuclei, aerosols =

airborne

total number of existing cases with respect to the entire population usually represented by a percentage of the population =

prevalence

measures the number of new cases over a certain time period, as compared with the general healthy population =

incidence

the total number of deaths in a population due to a certain disease =

mortality rate

the number of people afflicted with a certain disease =

morbidity rate

disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale =

endemic

when occasional cases are reported at irregular intervals =

sporadic

when prevalence of a disease is increasing beyond what is expected =

epidemic

epidemic across continents =

pandemic

which method is used to determine causative agent of a disease (a sequence of experimental steps for directly relating a specific microbe to a specific disease)?

Koch’s postulates

1) Finding a portal of entry
2) Attach firmly (to cell)/Adhesion
3) Invasion/Multiplication/Surviving host defense
4) Infection of target/Cause damage
5) disease
5) Exit host through portal of exit

steps in the development of an infection

Some pathogens produce a secretion system to insert specialized virulence proteins directly into the host cells, ex. Salmonella =

invasion factors

an example of an endotoxin is =

lipopolysaccharide

examples of exotoxins include =

hemolysins, a-b toxins

4 Stages of Clinical Infections =

incubation period, prodromal stage, period of invasion, convalescent period

Able to be passed easily from one person to another =

contagious

forms of direct contact for communicable diseases =

contact, droplets, vertical, biological vector