Module 6 chapter 15 Flashcards
What are the signs of a disease?
- Are objective and measurable
- Can be directly observed by a clinician
- Ex. having a high fever (body temp a lot higher than 37) is a sign of a disease because it can measured
What are vital signs?
- used to measure the body’s basic functions
- Include body temp (37), heart rate (60-100 beats per min), breathing rate (12-18 breaths per min), blood pressure (between 90/60 and 120/80 mm Hg)
- Changes in vital signs may be indicative of disease
What are other observable conditions other than vital signs that are a sign of disease?
- Presence of antibodies in a patient’s serum (liquid portion of blood that lacks clotting factors) can be observed and measures through blood test so it is a sign
- Antibodies not always a sign of disease as they can remain in the body after an infection has been resolved; also may develop in response to a pathogen that is in the body but not currently causing disease
What are symptoms of a disease
- They are subjective
- Are felt or experienced by the patient, but cannot be clinically confirmed or objectively measured
- Important when diagnosing disease, but are subject to memory bias and are difficult to measure precisely
- Some clinicians attempt to quantify symptoms by asking patients to assign a numerical value to their symptoms
- ex: Wong-Baker Faces pain-rating scale (0-10)
- ex: Skin conductance fluctuations: reflect sweating due to skin sympathetic nerve activity resulting from the stressor of pain
What are some examples of symptoms
- Nausea
- Loss of appetite
- Pain
What is a syndrome?
A specific group of signs and symptoms characteristic of a particular disease
What does it mean if a disease is asymptomatic or subclinical
- They do not present any noticeable signs or symptoms
What is an infectious disease?
- Any disease caused by the direct effect of a pathogen
What does it mean for a disease to be communicable?
- They are able to be spread from person to person through either direct or indirect mechanisms
What does it mean for an infectious communicable disease to be contagious
- It is easily spread from person to person
- Degree to which a disease is contagious usually depends on how the pathogen is transmitted
What is a iatrogenic disease (communicable)
- Diseases that are contracted as the result of a medical procedure
- Ex:
- After procedures involving wound treatments
- Catheterization
- Surgery, if the wound or surgical site becomes contaminated
What is a nosocomial disease (communicable)?
- Diseases acquired in hospital settings
- Sick patients bring in pathogens
- Hospital patients have weakened immune systems, making them more susceptible to infections
- Prevalence of antibiotics in hospital settings can select for drug-resistant bacteria that can cause very serious infections that are difficult to treat
What is a zoonotic disease (or zoonosis) (communicable)?
- Infectious diseases that are transmitted from animals to humans
- WHO says its when a pathogen is transferred from a vertebrate animal to a human, but sometimes used more broadly to include diseases spread from all animals (including invertebrates)
- Ex. rabies
What is a noncommunicable disease?
- Infections disease that is not spread from one person to another
- ex. tetanus
What is a noninfectious disease?
- Not caused by a pathogen
- Noncommunicable infectious disease
What are the 5 periods of disease
- Incubation
- Prodromal
- Illness
- Decline
- Convalescence
Incubation period
- Occurs in an acute disease after the initial entry of the pathogen into the host
- Pathogen beings multiplying in host
- Insufficient numbers of pathogen particles present to cause signs and symptoms of disease
- Can vary from a day or two (acute) or months or year (in chronic)
- Patient unaware that a disease is beginning to develop
What factors are involved in determining the lentgth of the incubation period
- Strength of pathogen
- Strength of the host immune defenses
- Site of infection
- Type of infection
- Size infectious dose received
Prodromal period
- After incubate period
- Pathogen continues to multiply and host beings to experience general signs and symptoms of illness, which typically result from activation of the immune system
- Ex: fever, pain, soreness, swelling, or inflammation
- Signs and symptoms too general to indicate a particular disease
Period of illness
- Happens after prodromal period
- Signs and symptoms of disease are most obvious and severe
Period of decline
- After period of illness
- Number of pathogen particles begins to decrease
- Signs and symptoms of illness being to decline
- Patients may become susceptible to developing secondary infections because their immune systems have been weakened by the primary infection
Period of convalescence
- Final period
- Patient generally returns to normal functions
- Some diseases may inflict permanent damage that the body cannot fully repair
Period of convalescence
- Final period
- Patient generally returns to normal functions
- Some diseases may inflict permanent damage that the body cannot fully repair
Summarize the classical version of Koch’s postulates and compare and contrast them with molecular Koch’s postulates
Describe virulence in terms of infectious dose and lethal dose
Use examples to explain primary pathogens versus opportunistic pathogens
Summarize the stages of pathogenicity
Use examples to describe the roles of portals of entry and exit in the transmission of disease
What do each of Koch’s postulates represent?
A criterion that must be met before a disease can be positively linked with a pathogen
- On order to determine this, tests are performed on laboratory animals and cultures from healthy and diseased animals are compared
What are Koch’s postulates?
- The suspected pathogen must be found in every case of disease and not be found in healthy individuals
- The suspected pathogen can be isolated and grown in pure culture
- A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1.
- The pathogen must be re-isolated from the new host and must be identical from postulate 2.
What was found wrong with Koch’s postulate 1
- Pathogens are not only found in diseased individuals
What was wrong with Koch’s postulate 2?
- All healthy test subjects are not equally susceptible to disease
- Individuals are unique in terms of microbiota and the state of their immune system at any given time
- Not all pathogens are microorganisms that can be grown in pure culture and animals cannot always serve as reliable models for human disease
- Can’t ethically test diseases in humans (postulate 3)
What is the premise for molecular Koch’s postulates?
- Not the ability to isolate a particular pathogen, but rather to identify a gene that may cause the organism to be pathogenic
- Not only explain infections caused by intracellular pathogens but also the existence of pathogenic strains of organisms that are usually nonpathogenic
What are the molecular Koch’s Postulates
- The phenotypes (sign or symptom of disease) should be associated only with pathogenic strains of a species
- Inactivation of the suspected gene(s) associated with pathogenicity should result in a measurable loss of pathogenicity
- Reversion of the inactive gene should restore the disease phenotype
What are some limitations of the molecular Koch’s postulates
- Genetic manipulation of some pathogens is not possible using current methods of molecular genetics
- Some diseases do not have suitable animals models, which limits the utility of both the original and molecular postulates
What is pathogenicity
The ability of a microbial agent to cause disease
What is virulence?
The degree to which an organism is pathogenic
- On a continuum
- On one end of the spectrum organisms are avirulent (not harmful) and on other end organisms are highly virulent
- Can be quantified using controlled experiments with laboratory animals
What are two important indicators of virulence?
- The median infectious dose (ID50)
- The median lethal dose (LD50)
- Both are typically determined experimentally using animals models
What is the median infectious dose?
The number of pathogen cells or virions required to cause active infection in 50% of inoculated animals
What is the median lethal dose
The number of pathogenic cells, virions, or amount of toxin required to kill 50% of infected animals
How do you calculate the ID50 and LD50?
- Each group of animals is inoculated with one of a range of known numbers of pathogen cells or virions
- The percentage of animals that have been infected or killed is plotted against the concentration of pathogen inoculated
What are two ways that pathogens can be classified?
As either primary pathogens or opportunistic pathogens
What is a primary pathogen?
Can cause disease in a host regardless of the host’s resident microbiota or immune system