Chap 14 Flashcards
Pathology
the study of disease
Etiology:
the cause of a disease
Pathogenesis:
the development of disease
Infection
invasion or colonization of the body by pathogens
Disease
an abnormal state in which the body is not performing normal functions
Human microbiome begins to be established
In utero
How is the human microbiome established?
More microorganisms acquired from food, people, and pets
The human microbiome remains throughout
life; very specific to you
Human Microbiome Project
analyzes relationships between microbial communities on the body and human health
Normal microbiota
permanently colonize the host and do not cause disease under normal conditions
Transient microbiota
may be present for days, weeks, or months
Opportunistic
If it has the ability to colonize somewhere else it probably will
Distribution and composition of normal microbiota are determined by many factors
Nutrients
Physical and chemical factors
Host defenses
Mechanical factors
H. pylori causes
Stomach ulcers
Vaginal birth microbes
prevalently Lactobacillus and Bacteroides
Cesarean birth microbiome
microbiome resembles the human skin
Staphylococcus aureus
Microbial antagonism (competitive exclusion)
is a competition between microbes
Normal microbiota protect the host by:
Competing for nutrients
Producing substances harmful to invading microbes
Affecting pH and available oxygen
Symbiosis
relationship between normal microbiota and the host
Commensalism
one organism benefits, and the other is unaffected
Mutualism
both organisms benefit
Parasitism
One organism benefits at the expense of the other
opportunistic pathogens can be pathogenic when
it grows too much, or it grows somewhere where its not supposed to
first of koch’s postulates
The same pathogen must be present in every case of the disease.
2nd of Koch’s postulates
The pathogen must be isolated from the diseased host and grown in pure culture.
3rd of Koch’s postulates
The pathogen from the pure culture must cause the disease when it’s inoculated into a healthy, susceptible laboratory animal.
4th of Koch’s postulates
The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.
Koch’s postulates are used to
prove the cause of an infectious disease
Exceptions to Koch’s postulates
- Some pathogens can cause several disease conditions
- Some pathogens cause disease only in humans
- Some microbes have never been cultured
Symptoms:
changes in body function that are felt by a patient as a result of disease
Signs:
changes in a body that can be measured or observed as a result of disease
Syndrome:
a specific group of signs and symptoms that accompany a disease
Communicable disease
a disease that is spread from one host to another
Contagious diseases
diseases that are easily and rapidly spread from one host to another
Noncommunicable disease
a disease that is not spread from one host to another
The study of where and when diseases occur, and how they are transmitted
epidemiology
Incidence
number of people who develop a disease during a particular time period
Prevalence
number of people who develop a disease at a specified time, regardless of when it first appeared
Prevalence takes into account
both old and new cases
Epidemiology is important because
We learn how to treat and prevent various diseases
Expected prevalence
prevalence that is expected based on patterns established by past observations.
sporadic diseases
only a few cases occur in that region
Endemic disease
disease normally and continuously occurs there at a fairly stable rate.
Epidemic disease
disease occurs at a significantly higher rate than what would normally be expected.
Pandemic disease
There is an epidemic on more than one continent at the same time
disease that occurs only occasionally
sporadic disease
disease constantly present in a population
Endemic disease
disease acquired by many people in a given area in a short time
Epidemic disease
Worldwide epidemic
Pandemic disease
Acute disease
symptoms develop rapidly but the disease lasts only a short time
Chronic disease
symptoms develop slowly
Subacute disease
intermediate between acute and chronic
Latent disease
causative agent is inactive for a time but then activates and produces symptoms
Herd immunity
immunity in most of a population
Local infection
pathogens are limited to a small area of the body
Systemic (generalized) infection
an infection throughout the body
Focal infection
systemic infection that began as a local infection
Sepsis
toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection
Bacteremia
bacteria in the blood
Septicemia
also known as blood poisoning; 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 factors
Make the body more susceptible to disease
Examples of predisposing factors
Gender
Inherited traits, such as the sickle cell gene
Climate and weather
Lack of vaccination
Fatigue
Age
Lifestyle
Nutrition
Chemotherapy
Incubation period
interval between initial infection and first signs and symptoms
Prodromal period
short period after incubation; early, mild symptoms
Period of illness
disease is most severe
Period of decline
signs and symptoms subside
Period of convalescence
body returns to its prediseased state
Reservoirs of infection
Continual sources of infection
Nonliving reservoirs examples
soil and water
Example of human reservoirs
Carriers may have inapparent infections or latent diseases
Examples of animal reservoirs
Zoonoses are diseases transmitted from animals to humans
carriers
may have inapparent infections or latent diseases
Zoonoses
diseases transmitted from animals to humans
Direct contact transmission
requires close association between the infected and a susceptible host
Congenital transmission
transmission from mother to fetus or newborn at birth
Indirect contact transmission
spreads to a host by a nonliving object called a fomite
Formite
inanimate object that can spread disease to a new host when contaminated with infectious agents.
Droplet transmission
transmission via airborne droplets less than 1 meter
Vehicle transmission
Transmission by an inanimate reservoir
Vehicle transmission can be
Airborne
Waterborne
Foodborne
Examples of vectors
Arthropods, especially fleas, ticks, and mosquitoes
Vectors transmit disease by two methods
- Mechanical transmission
- Biological transmission
Mechanical transmission
arthropod carries pathogen on its feet
Biological transmission
pathogen reproduces in the vector; transmitted via bites or feces
Infectious diseases are transmitted from either
- Host’s portal of exit
- Reservoir to new host
Three major categories of transmission
- Contact transmission
- Vehicle transmission
- Vector transmission
Types of Contact transmission
1.direct contact, 2.indirect contact or 3.droplets
Examples of contact transmission
touching, kissing, sexual intercourse
transfer from mother to fetus
or from one site to another on one person, such as between the nose and eye
Droplet transmission can happen during
- exhaling, speaking, coughing, sneezing
Indirect contact
involves spreading of pathogens by inanimate objects called fomites
Spread of pathogens via an aerosol; dust or droplets traveling further than 1 meter
Airborne
Waterborne transmission is a major mode of transmission for
many GI diseases like cholera
How does cholera usually get transmitted?
Fecal material enters the water supply
Foodborne transmission
also a typical cause of GI diseases
pathogens enter food that wasn’t properly prepared, or is contaminated with fecal material
nosocomial infections
Acquired while receiving treatment in a health care facility
Prevalence of HAIs
Affect 1 in 25 hospital patients
2 million per year infected; over 70,000 deaths
UTI
40% of HAIs
commonly acquired during removal or insertion of urinary catheters
usually involve normal flora of patient or employee
Surgical wound infection
second most common type of HAI
usually caused by normal skin flora
Lower respiratory infections
third most common HAI , usually associated with respiratory devices
Cutaneous infections commonly occur in
newborns or burn patients
fourth most common HAI
cutaneous infections
Bacteremia
5th most common HAI,
usually due to intravenous catheterizations or injections
All other HAI percentage
11%
Why are patients susceptible to nosocomial infections?
-weakened defenses
-resistant microbes
-invasive procedure
-movement of staff and visitors
HAIs result from:
Microorganisms in the hospital environment
Weakened status of the host
Chain of transmission in a hospital
Compromised host
an individual whose resistance to infection is impaired by disease, therapy, or burns
types of universal precautions
- Standard precautions
- Transmission-based precautions
Standard precautions
basic, minimum practices
Transmission-based precautions
supplemental to standard precautions; designed for known or suspected infections
Examples of transmission-based precautions
Contact precautions
Droplet precautions
Airborne precautions
How do you control of Healthcare-Associated Infections
Reduce number of pathogens
Infection control committees
How do you reduce the number of pathogens?
1.Handwashing
2. Disinfecting tubs used to bathe patients
3. Cleaning instruments scrupulously
4. Using disposable bandages and intubation
Emerging infectious diseases
Diseases that are new, increasing in incidence, or showing a potential to increase in the near future
Most emerging infectious diseases are
Most are zoonotic, of viral origin, and likely to be vector-borne
Contributing factors of EIDs
-Genetic recombination
-Evolution of new strains
-Widespread use of antibiotics and pesticides
(Antibiotic-resistant strains)
Changes in weather patterns
(Hantavirus)
Evolution of new strains example
E. coli O157:H7 and avian influenza (H5N1)
new strains example
serovars like Vibrio cholerae O139
How can changing weather patterns increase EIDs
- increase the distribution and survival of reservoirs and vectors,
How do genetic recombinations lead to EIDs?
New strains, such as E. coli O157:H7 and avian influenza (H5N1), may result from genetic recombination between organisms.
How does modern transportation contribute to EIDs?
Known diseases, such as Zika virus disease, chikungunya, dengue, and West Nile encephalitis, may spread to new geographic areas by modern transportation. This was less likely 100 years ago, when travel took so long that infected travelers either died or recovered during passage.
How can insect vectors contribute to EIDs?
Aedes aegypti, A. albopictus
insect vectors brought by human travelers
How do natural disasters contribute to EIDs?
Previously unrecognized infections may appear in individuals living or working in regions undergoing ecological changes brought about by natural disaster, construction, wars, and expanding human settlement.
the incidence of coccidioidomycosis increased tenfold following the Northridge earthquake of 1994
natural disaster in california led to emerging infectious disease
How does animal control contribute to EIDs?
The increase in Lyme disease in recent years could be due to rising deer populations resulting from the killing of deer predators.
How do failures in public health measures contribute to EIDs?
the failure of adults to get a diphtheria booster vaccination led to a diphtheria epidemic in the newly independent republics of the former Soviet Union in the 1990s.
Bioterrorism
use of pathogens or toxins to produce death and disease in humans, animals, or plants as an act of violence and intimidation,
How does bioterrorism contribute to EIDs?
he pathogens or toxins can be disseminated through aerosolization, food, human carriers, water, or infected insects leading to EIDs
Functions of epidemiologists
Determine etiology of a disease
Identify other important factors concerning the spread of disease
Develop methods for controlling a disease
Assemble data and graphs to outline incidence of disease
Mapped the occurrence of cholera in London
1848-1849
John snow
Showed that handwashing decreased the incidence of peurperal sepsis 1846-1848
Ignaz Semmelweis
1858 showed that improved sanitation decreased the incidence of epidemic typhus
Florence Nightingale
Descriptive epidemiology
collection and analysis of data
-Snow
Analytical epidemiology
analyzes a particular disease to determine its probable cause
-nightingale
Experimental epidemiology
involves a hypothesis and controlled experiments
- Semmelweis
Clinical trial
Test and control group
Function of CDC
Collects and analyzes epidemiological information in the United States
CDC publishes this
Morbidity and Mortality Weekly Report (MMWR)
Morbidity
incidence of a specific notifiable disease
Mortality
deaths from notifiable diseases
Notifiable infectious diseases
diseases in which physicians are required to report occurrence
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 relation to the population in a given time
MRSA is cultured on
Blood cultures grown on mannitol-salt agar; coagulase-positive; gram-positive cocci
92% of healthcare strains
Strain USA100
Strain USA300
89% of community-acquired strains
