CHAPTER 14 Flashcards
What does symbiosis mean?
to live together
What are the types of symbiosis?
mutualism, commensalism, amensalism, parasitism
What happens in mutualism?
both organisms benefit ex. bacteria in human colon
What happens in commensalism?
organism 1 benefits, organism 2 neither benefits or harmed; ex, mites in human hair follicles
What happens in amensalism?
organism 1 harmed, organism 2 neither benefits or harmed, ex. fungus secreting an antibiotic
What happens in parasitism?
organism 1 benefits, organism 2 harmed, ex. TB in human lung
What are the 2 types of microbiota?
resident microbiota and transient microbiota
What are resident microbiota?
part of normal microbiota, mostly commensal
What are transient microbiota?
remain in body for short time, cannot persist in body, same regions as resident microbiota
How does a human acquire normal micorbiota?
first acquired during birthing process and then in the first few months of life; microbiome begins to develop during birthing process
How do normal microbiota become opportunistic pathogens?
conditions provide opportunities for pathogens-
intro of normal microbiota into unusual site of body;
immune suppression (AIDs);
changes in normal microbiota (C. albicans);
stressful conditions
What are reservoirs of infection?
sites where pathogens are maintained as a source of infection
What are the 3 types of reservoirs?
animal reservoirs, human carriers, nonliving reservoirs
What are zoonoses?
diseases that naturally spread from animal host to humans; can be direct contact with animal or waste, eating animal, or bloodsucking arthropods
How are human carriers reservoirs?
asymptomatic infected people can infect others, healthy carriers may have defensive systems that protect them
Examples of nonliving resevoirs?
soil, water, food; contamination often due to feces or urine
What is contamination?
the mere presence of microbes in or on the body
What is infection?
When organism evades body’s external defenses, multiplies, and becomes established in the body
What are the 3 major pathways for portal of entry?
skin, mucous membranes, placenta
How does skin work as barrier/ portal of entry?
outer layer of dead skin cells serves as barrier, some pathogens can enter through cuts or burrowing into outer layers of skin and digesting
How do mucous membranes work as portal of entry?
provides most, warm environment hospitable to pathogens, respiratory tract most common site of entry
How does placenta work as portal of entry?
usually forms effective barrier, but pathogens may cross placenta and infect fetus
What is role of adhesion in infection?
process by which microorganisms attach themselves to cells, use adhesion factors (specialized structures and attachment molecules)
What is disease result of?
invading pathogen altering normal body functions
What are symptoms?
subjective characteristics of disease felt only by patient
What are signs?
objective manifestations of disease observed or measured by others
What is a syndrome?
symptoms and signs that characterize a disease or abnormal condition
What are asymptomatic or subclinical infections?
lack symptoms but may still have signs of infection
What is etiology?
study of the cause of disease
What is germ theory of disease?
infections by pathogenic microorganisms cause disease (Koch)
What did Robert Koch develop?
a set of postulates one must satisfy to prove that a particular pathogen causes a particular disease
What are exceptions to Koch’s postulates?
some cultures cant be cultured in lab; diseases can be caused by combo of pathogens; ethical considerations that prevent using postulates method on human host
What are the difficulties in satisfying Koch’s postulates?
diseases can be caused by more than one pathogen, some pathogens are ignored as cause, epidemiological studies used when postulates can’t be satisfied
What is pathogenicity?
ability of microorganism to cause disease
What is virulence?
degree of pathogenicity
What are the virulence factors?
adhesion factors, biofilms, extracellular enzymes, toxins, antiphagocytic factors
What are extracellular enzymes?
secreted by pathogen, dissolve structural chemicals in the body; help pathogen maintain infection, invade, and avoid body defenses
What are the microbial extracellular enzymes that aid in virulence?
coagulases, kinases, hyaluronidase, collagenase, IgA proteases, mucinase, keratinase
What do coagulases do?
coagulate fibrinogen ex. S. aureus
What do kinases do?
digest fibrin clots ex. streptokinase
What does hyaluronidase do?
digest hyaluronidase polysaccharides that holds cells together ex. staphylococci
What does collagenase do?
breaks down collagen ex. clostridium
What do IgA proteases do?
destory IgA antibodies ex. neisseria
What does mucinase do?
digests protective coating on mucous membranes ex. amoebic dysentery
What does keratinase do?
digests keratin in skin and hair ex. fungal infections like ringworm
What are toxins?
chemicals that harm tissues or trigger host immune responses that cause damage
What is toxemia?
refers to the presence of toxins in the bloodstream
What are the 2 types of toxins?
endotoxins and exotoxins
Know exotoxins vs endotoxins chart on powerpoint*
slides 43 and 44
What are antiphagocytic factors?
factors that prevent phagocytosis by the host’s phagocytic cells, allows pathogen to remain in host for longer time
What is bacterial capsule?
composed of chemicals not recognized as foreign, difficult for phagocytes to engulf, ex streptococcus pneumoniae
What are antiphagocytic chemicals?
prevent fusion of lysosome and phagocytic vesicles
What do leukocidins do?
directly destroy phagocytic wbc’s
What are the 5 stages of infectious disease?
incubation period, prodromal period, illness, decline, convalescence
What is incubation period?
no signs or symptoms, time between infection and occurrence of first symptom
What is prodromal period?
vague, general symptoms
What is illness stage?
most severe signs and symptoms
What is decline stage?
declining signs and symptoms
What is convalescence stage?
no signs or symptoms
What are the portals of exit?
many portals of exit are same as portals of entry, often leave host in materials the body secretes or excretes
What are the modes of transmission?
contact, vehicle, vector
What is direct contact transmission?
usually involves body contact between hosts
What is indirect contact transmission?
pathogens spread from host to host by fomites
What is droplet transmission?
spread of pathogens in droplets of mucus by exhaling, coughing, and sneezing
What is airborne transmission?
when pathogens travel more than 1 m via an aerosol
What is waterborne transmission?
important in spread of GI diseases, fecal-oral infection
What is foodborne transmission?
spread of pathogens in and on food
What is bodily fluid transmission?
blood, urine, saliva can carry pathogens
What are biological vectors?
transmit pathogens and serve as host for some stage of pathogen’s life cycle, biting arthropods
What are mechanical vectors?
passively transmit pathogens present on their body to new hosts
How is frequency of disease measured?
incidence and prevalence
What is descriptive epidemiology?
careful tabulation of data concerning a disease, try to identify index (first) case of disease; John snow started earliest descriptive epidemiology
What is analytical epidemiology?
seeks to determine the probable cause, mode of transmission, and methods of prevention
What is experimental epidemiology?
tests a hypothesis concerning the cause of disease, application of koch’s postulates
What are the types of nosocomial infections?
exogenous, iatrogenic, endogenous, superinfections
What are exogenous nosocomial infections?
pathogen acquired from health care environment
What are endogenous nosocomial infections?
pathogen arises from normal microbiota within patient
What are iatrogenic nosocomial infection?
results from modern medicine procedures
What are superinfections?
use of antimicrobial drugs inhibits some resident microbiota, allowing other microbes to thrive
What is most affective way to reduce nosocomial infections?
handwashing
