Chapter 14 Flashcards
pathology
the study of disease
etiology
the study of the cause of a disease
pathogenesis
the development of disease
infection
colonization of the body by pathogens
disease
an abnormal state in which the body is not functioning normally
transient microbiota
may be present for days, weeks or months
normal microbiota
permanently colonize the host
symbiosis
the relationship between normal microbiota and the host
- commensalism- one organism benefits and other is unaffected
- mutualism- both organisms benefit
- parasitism- one organism benefits at the expense of the other
- some normal micro iota are opportunistic pathogens
microbial antagonism
a competition between microbes
normal microbiota protect the host by:
- occupying niches that pathogens might occupy
- producing acids
- producing bacteriocins (toxins produced by bacteria against other types of bacteria
probiotics
are live microbes applied to or ingested into the body, intended to exert a beneficial effect
- yogurts that are advertised as promoting regularity
Kochs Postulates
-used to prove the cause of an infectious disease
- pathogen present in every case of disease
- pathogen isolated from the diseased host and grown in pure culture
- pathogen from pure culture must cause disease when inoculated into healthy animal
- pathogen must be isolated from the diseased animal shown to be same as original
symptom
a change in body function that is felt by a patient as a result of disease (pain)
sign
a change in a body that can be measured or observed as a result of disease (fever)
syndrome
a specific group of signs and symptoms that accompany a disease
communicable disease
a disease that is spread from one host to another (chicken pox, TB, measles, mumps)
contagious disease
a disease that is easily spread from one host to another (chicken pox and measles)
noncommunicable disease
a disease that is not transmitted from one host to another (Clostridium tetani)
incidence
fraction of a population that contracts a disease during a specific time, incidence only looks at the new cases during a period of time
prevalence
fraction of a population having a specific disease at a given time. This takes into account the old and new cases at a specific point in time
sporadic disease
disease that occurs occasionally in a population
endemic disease
disease constantly present in a population
epidemic disease
disease acquired by many hosts in a given area in a short time
pandemic disease
worldwide epidemic
herd immunity
immunity in most of a population, important concept, When enough people in a community are immune to a disease, the spread of the disease is stopped
acute disease
symptoms develop rapidly (influenza)
chronic disease
disease develops slowly (hepatitis B)
subacute disease
symptoms between acute and chronic (sub acute sclerosing panencephalitis)
latent disease
disease with a period of no symptoms when the pateint is inactive (chicken pox –> shingles)
local infection
pathogens are limited to a small area of the body
systemic infection
an infection throughout the body
focal infection
systemic infection that began as a local infection but spread to other parts of the body
bacteremiz
bacteria in the blood
septicemia
growth of bacteria in the blood
toxemia
toxins in the blood
viremia
viruses in the blood
primary infection
acute infection that causes the initial illness
secondary infection
opportunistic infection after a primary (predisposing) infection
subclinical disease
no noticeable signs or symptoms (inapparent infection)
Predisposing Factos
-make the body more susceptible to disease
- short urethra in females compared to males
- inherited trait such as the sickle- cell gene
- climate and weather
- fatigue
- age- very young and very old more susceptible to disease
- lifestyle- nutrition, exercise, work conditions
- chemotherapy
reservoirs of infection
- are continual sources of infection
- Human- AIDS, gonorrhea
- carries may have inapparent infections or latent diseases
- animal- rabies, lyme disease
- some zoonoses (animal diseases) may be transmitted to humans
- nonliving- botulism, tetanus
- spores in soil
direct transmission of disease
requires close association between infected and susceptible host, no intermediate object involved
indirect transmission of disease
spread by fomites (non-living object that transfers microbes between people) (tissues)
droplet transmission of disease
transmission via airborne droplets discharged into the air by coughing, sneezing and talking, moist droplets travel less than 1 meter
droplet nuclei- transmission of disease
- dried droplets of mucus and saliva that occur after a person coughs or sneezes
- smaller than 5 microns: this is small enough to carry at least one bacteria and many viruses
- small enough to remain airborne for a long time
- carried by air currents
- can be breathed deep into lungs
vehicle transmission of disease
transmission by an inanimate reservoir (food and water)
vectors; transmission of disease
-arthropods, especially fleas, ticks and mosquitoes
- mechanical- arthropod carries pathogen on feet, dog carries parasites
- biological- pathogen reproduces in vector
nosocomial (hospital- acquired infections)
- acquired as a result of hospital stay
- 5-15% of all hospital patients acquire nosocomial infections
how are nosocomial infections spread?
- are transmitted by direct contact between staff members and patients and between patients
- fomites such as catheters, syringes, and respiratory devices can transmit nosocomial infections
what precautions should be taken to prevent nosocomial infections?
- aseptic techniques can prevent nosocomial infections
- careful hand washing between patients
- hospital infection control staff members are responsible for overseeing the proper cleaning, storage and handling of equipment and supplies
EID’s
- diseases that are new, increasing in incidence, or showing a potential to increase in the near future
- contributing factors
- genetic recombination between organisms
- E.coli 0157, Avian influenza (H5N1)
- genetic recombination between organisms
- inappropriate use of antibiotics and pesticides encourage growth of resistant strains
- antibiotic resistan strains
- changes in weather patterns
- Hantavirus may be more common because dry weather has promoted the right conditions for the rat carriers and transmission
- modern transportation- short level time between continents (west nile virus)
- ecological disaster, war, and expanding human settlement (coccidioidomycosis)
- animal control measures- humans moving into natural areas where deer live (lyme disease)
- public health failure- maintaining life-long immunity by vaccination (diphtheria)
crossing the species barrier
understanding the possibility of genetic recombination in other hosts
epidemiology
- the study of where and when diseases occur
- show different aspects of curves (seasonal differences)
Various epidemic curve
- point-source epidemic- food poisoning at an event
- common-source epidemic- many people exposed to common source (polluted drinking eater)
- Propagated epidemic- spread from person to person
morbidity
incidence of a specific notifiable disease
mortality
deaths from notifiable diseases
morbidity rate
number of people affected in relation to the total population in a given time period
mortality rate
number of deaths from a disease in a relation to the population in a given time
