chap 4 Flashcards
Pathogen:
disease causing microorganism
Pathology:
scientific study of disease (pathos = suffering; logos = science)
Etiology:
causative agent of a disease
Pathogenesis,
the manner in which a disease develops
Infection:
invasion or colonization of the body by pathogenic microorganisms
Disease:
it occurs when an infection results in any change from a state of health. It is an abnormal state in which part or all of the body is not properly adjusted or
incapable of performing its normal functions
Host:
is an organism that shelters and supports the growth of pathogens
normal microbiota or normal flora
are microbes that are on or in a host, but do not cause disease
transient microbiota
composed of microbes that are present for various periods and then disappear.
Microbial antagonism
normal microbiota can prevent pathogens from causing an infection;
Normal microbiota protect the host against colonization by potentially pathogenic microbes by
competing for nutrients, producing substances harmful to the invading microbes, and affecting conditions such as pH and available oxygen
Symbiosis:
relationship between the normal microbiota and the host
Symbiotic Relationship Types
- Commensalisms: One organism benefits, the other is unaffected (harmless)
- Mutualism: Both organisms benefit (helpful)
- Parasitism: One organism benefits and the other is harmed (harmful)
Opportunists (Opportunistic Pathogens)are
members of the normal microflora that do not usually cause disease but can be pathogenic under certain circumstances:
- Host immunosuppression
- Elimination of microbial antagonism
Opportunism:
Organism doesn’t cause disease unless appropriate conditions exist (potentially harmful)
Infectious disease :
is a disease caused by a microorganism and therefore potentially infinitely transferable to new individuals.
Disease
A change away from a normal state of health to an abnormal state in which health is diminished.
Sign
an objective change in body function (e.g., health) that may be observed and measured by an individual in addition to the patient.
Contrast with symptom.
Symptom
A symptom is a changes in body function felt by the patient.
Symptoms are not measurable by a physician.
Contrast with sign.
Sequelae
Residual effects of the disease process. Essentially the unrepaired wear and tear caused by a disease.
Syndrome
A specific group of symptoms or signs that always accompanies a specific disease
Diagnosis
Identification of the disease
Communicable disease:
An infectious disease that readily spreads from person to person either directly or indirectly-Exp: genital herpes, tuberculosis, …
Is readily easily caught, especially from an infected person.
Contagious disease:
Can easily spread from one person to another; however some communicable diseases can be contagious diseases like chickenpox for exp.
Sporadic disease:
particular disease that occurs only occasionally like typhoid fever in USA
Endemic disease:
disease constantly present in a population like common cold.
Epidemic disease:
if many people in a given area acquire a certain disease in a relatively short period of time. Like influenza
Pandemic disease:
an epidemic disease that occurs worldwide
Acute Infection:
develops quickly and lasts shortly, for ex: Influenza, food poisoning
Chronic Infection:
develops slowly and lasts for a long period of time , for ex: tuberculosis & hepatitis
Subacute Infection:
is the gray zone between acute and chronic
Latent Infection:
is sign-less or symptom-less for a long period of time, a while before signs and symptoms appear i.ecausative agent remains inactive for a period of time and then becomes active to produce symptoms for ex: AIDS
Subclinical (Inapparent) infection:
that doesn’t cause any clear illness like Poliovirus or Hepatitis A for example that can be carried by people who never develop the illness.
Local infection:
affects a small area of the body, for ex: Abscesses
Systemic (generalized) infection:
Microrganisms or their products are spread to the body by lymph or by blood, for ex: measles
Focal infection:
it begins as local and then it spreads beyond the local area like Tetanus (local infection that causes symptoms in other parts of the body)
Sepsis
is a toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection.
Septicemia, also called blood poisoning,
is the growth of pathogens in the blood. Septicemia is a common example of sepsis.
bacteremia.
The presence of bacteria in the blood without multiplication
Toxemia
refers to the presence of toxins in the blood (as occurs in tetanus)
Viremia
refers to the presence of viruses in blood.
A primary infection
is an acute infection that causes the initial illness (of a not currently infected person).
A secondary infection:
- an infection that quickly follows a primary infection
- A second infection that occurs during or after treatment of a primary infection.
- Is caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses.
- It may result from the treatments (superinfection)or from alterations in the immune system.
DiseaseA-Predisposing Factors:
They affect the occurrence of the disease by making the body more susceptible to a disease and may alter the course of the disease
Examples include:
-Gender:for ex females have higher incidence of urinary tract infections than males
-Climate and weather:seem to have effect on the incidence of infectious diseases. Ex: In temperate regions the incidence of respiratory diseases increase during the winter
-Nutrition, level of fatigue, age, environment, socioeconomic status, …
5 stages of disease development can be identified:
- Incubation period: is the time interval between the initial infection and the first appearance of any signs or symptoms, it varies between several hours to several weeks
2.Prodromal period: that follows the incubation period, it’s characterized by the appearance of the first mild signs and symptoms - Illness: in this stage the disease is most acute and all disease signs and symptoms are present. Ex: The person shows sign and symptoms of disease like fever, muscle pain,etc.. In general, the patient’s immune response and other defense mechanisms overcome the pathogen, if not the patient dies during this period
- Period of decline: the signs and the symptoms subside, Ex: the fever decreases the feeling of malaise also decreases.
- Period of convalescence: the body returns to its pre-diseased state
NB:During incubation period, people can serve as reservoirs of disease and can easily spread infections to other people
A-Reservoirs of Infection
Continual source of infection
Can either be a living organism or an inanimate object such as soil and water that provides a pathogen with adequate conditions for survival, multiplication and transmission
Human, animal, or nonliving
Human:
The disease can be transmitted to others directly or indirectly
Some people can harbor pathogens and transmit them to others without exhibiting any signs of illness. These people, called carriers are important living reservoirs.
Animal
- Both wild and domestic are living reservoirs of MO that can cause human diseases.
- Diseases that occur primarily in wild and domestic animals and can be transmitted to humans are called zoonosesfor ex: Rabies (found in bats, skunks, foxes, dogs, and coyotes), and Lyme disease (found in field mice)
- The transmission of the disease can occur via different routes by direct contact with infected animals or with domestic pet waste, by contamination of food and water, by consuming infected animal products, or by insect vectors
c-NonlivingThe 2 major nonliving reservoirs are soil and water
eg. *Clostridium botulinum, the bacterium that causes botulism; Clostridium tetani the bacteria that causes tetanus in soil
- Water that has been contaminated by the feces of humans and other animals is a reservoir for several pathogens, notably those responsible for gastrointestinal diseases. These include Vibrio cholerae which causes cholera and Salmonella typhi which causes typhoid fever.
- Other nonliving reservoirs include foods that are improperly prepared or stored. They may be sources of diseases such as trichinellosis and salmonellosis.
B-Transmission of Disease
Three Main Routes:
Contact, vehicle and vectors
1-Contact Transmission
Direct :a.k.aperson-to-person transmission,
- Is the direct transmission of an agent by physical contact between its source and a susceptible host; no intermediate object is involved
- The most common forms of direct contact transmission are touching, kissing, and sexual intercourse
- It can also occur from animal to human.
contact transmission 2 : Indirect:
•The agent of disease is transmitted from its reservoir to a susceptible host by a nonliving object: fomites.
•Ex: drinking cups, eating utensils, toys, money, thermometers, tissues, towels, bedding, etc..
Droplet:
•Microbes are spread in droplets that travel only short distances.
•These droplets are discharged into the air by coughing, sneezing, laughing, etc.. Exp: Influenza, pneumonia, etc..
2-Vehicle Transmission:
Transmission of disease by a medium such as water, soil, food, & air
Other media include blood and other body fluids, drugs, and intravenous fluids.
Waterborne transmission:
Pathogens are usually spread by water contaminated with untreated or poorly treated sewage
Ex: cholera, waterborne shigellosis, and leptospirosis.
Foodborne transmission:
Pathogens are generally transmitted in foods that are incompletely cooked, poorly refrigerated or prepared under unsanitary conditions
Foodborne pathogens cause disease like food poisoning Foodborne pathogens cause diseases such as food poisoning and tapeworm infestation.
Airborne transmission:
Refers to the spread of infection in dust that travel more than 1 meter from the reservoir to the host. Dust particles can harbor different pathogens like Streptococci and Staphylococci
For example, microbes are spread by droplets, which may be discharged in a fine spray from the mouth and nose during coughing and sneezing
Staphylococciand Streptococcican survive on dust and be transmitted by the airborne route.
3-Vectors:
Arthropods are the most important group of disease vectors
Mechanical transmission
•Is the passive transport of pathogens on the insect’s body parts, pathogens can be transferred to food
Biological transmission
- Is an active process and is more complex. The insect bites an infected person or animal and ingests some of the infected blood.
- The pathogens reproduce in the vector and the increase in the number of pathogens increases the possibility that they will be transmitted to another host
A nosocomial infection
is acquired as result of a stay in a hospital, nursing home, or other health-care facility.
About 5-15% of all hospitalized patients acquire nosocomial infections
nosocomial infection results from the interaction of several factors:
- Microorganisms in the Hospital:
•Certain normal microbiota are often responsible for nosocomial infections when they are introduced into the body through such medical procedures as surgery and catheterization.
•Opportunistic, drug-resistant gram-negative bacteria are the most frequent causes of nosocomial infections.
2-The Compromised Host (The weakened status)
•Patients with burns, surgical wounds, and suppressed immune systems are the most susceptible to nosocomial infections.
3-The chain of transmission:
a. Nosocomial infections are transmitted by direct contact between staff members and patient and between patients.
b. Fomites such as catheters, syringes, and respiratory devices can transmit nosocomial infections. And sometimes through the ventilation system.
The control of Nosocomial infections
- Aseptic techniques can prevent nosocomial infections, handling contaminated materials carefully, insisting on frequent hand washing, educating and training staff members about basic control measures.
- Hospital infection control staff are responsible for the overseeing of proper cleaning, storage, and handling of equipment and supplies
* Accredited hospitals should have an infectious control committee. The role of this committee is to identify problem sources such as antibiotic resistant strains and improper sterilization
