LO 2 Flashcards
Define: Normal Flora
Microorganisms growing in or on the body all the time without causing injury to the host
- They permanently reside on our bodies and do not produce disease under normal circumstances
Define: Pathogenic
Capable of causing disease
What is the composition of normal flora?
Fairly constant for a given site; but varies depending on the site ( ex. the flora in the mouth is different then normal flora of the intestine or skin)
Which area of the body has the greatest amount of normal flora?
The large intestine has the greatest normal flora population
Define: Escherichia coli (E.coli) and where is it located?
E. coli is a rod-shaped bacterium (Bacilli- gram negative) found in the feces
Normal intestinal flora plays an important role in what?
Food digestion and evacuation of feces
What type of bacteria(normal flora) is found in mucous membrane of the upper respiratory tract? And what is their role?
Streptococci of the viridans group. They occupy attachment sites on host cells and prevent pathogenic bacteria from invading the respiratory tissue
What type of normal flora bacteria is found on the skin?
Staphylococci. (Live on a cool, dry, salty surface) Main normal flora on the skin. It is gram positive & blue
What are the two factors that affect Normal Flora? How?
1) Excess moisture on the skin = increase in staphylococci on skin
2) Antibiotic use = alters normal flora as the sensitive bacteria are killed allowing more resistant strains to predominate
Define: Contamination
Microorganisms present on the body (on a site where they are not expected) but they are not growing or causing damage to the host
- ex. saliva on skin
Define: Colonization
Microorganisms present and growing in or on the body but without causing any damage to the host
Define: Disease
Microbes multiplying in the host and causing damage to the host (it is evident and measurable)
Define: Infection
Often used to mean the same as disease (Microbes multiplying in the host and causing damage to the host) but also used to indicate growth of microbes in the host before disease symptoms become evident.
- Has been invaded with a pathogenic organism but there are no signs of lasting host damage
HIV/ AIDS infection or disease?
A person may be infected with HIV but show no signs of injury for some time. Once the symptoms of AIDS becomes evident, the host is described as having the disease AIDS
The lining of the urinary bladder is normally sterile. Bacteria will occasionally grow on the bladder mucosa without causing any disease or harm to the host. The term covering this relationship is ________
Colonization
The bacteria causing tuberculosis multiply inside white blood cells of the body for several weeks without causing any injury to the host. The person is described as being ____ with tubercle bacilli. Several weeks later symptoms of tuberculosis become evident and the person is said to now have the ______
The bacteria causing tuberculosis multiply inside white blood cells of the body for several weeks without causing any injury to the host. The person is described as being infected with tubercle bacilli. Several weeks later symptoms of tuberculosis become evident and the person is said to now have the disease
Throat cultures of most individuals with no evidence of sore throats will show viridans _____. These streptococci are ______.
Throat cultures of most individuals with no evidence of sore throats will show viridans streptococci. These streptococci are normal flora.
Staphylococcus aureus growing in a surgical incision causing swelling and inflammation would be described as ______
Staphylococcus aureus growing in a surgical incision causing swelling and inflammation would be described as infection.
Fecal bacteria on the hands of a person visiting the bathroom and failing to wash their hands after this visit would be called ______ as long as the bacteria were not growing and injuring the host
Fecal bacteria on the hands of a person visiting the bathroom and failing to wash their hands after this visit would be called contamination as long as the bacteria were not growing and injuring the host
Define: Pathogen
A disease-causing organism
Define: Virulence
The degree of pathogenicity
What are the factors of virulence? (4)
1) Enzymes that dissolve hyaluronic acid (tissue cement), collagen and fibrin clots, allowing bacteria to spread faster in the tissue
2) Substances that destroy RBC, releasing iron necessary for bacterial growth
3) Substances that destroy WBC, weakening the body defence
4) Capsules, or slimy coatings, which prevent attachment of phagocytic (eating) white blood cells
Define: Non-pathogen
An organism unable to cause disease
* Most common type of bacteria
Define: Low grade pathogen or opportunistic pathogens
They are non-pathogenic under most condition but may cause disease when the host’s defenses are lowered by predisposition conditions
- Only causing disease when the host defenses are lowered
- Only become bad when they have the opportunity to
Define: Exotoxins
- A bacterial product excreted from the cells and causing damage to specific host tissues
- Gram positive (blue)
- Exotoxins are carried away from the infection site by blood or along nerve cells
- Attack a specific target tissue
Define: Endotoxins
- A bacterial product that is part of the cell wall causing nonspecific damage to a variety of host tissues
- Gram negative (pink); located in the cell wall
- Released only when the bacterial cells are disrupted
- Can result in fever, aches, drop in blood pressure, circulatory collapse when accompanying bacterial infections
What is the difference between gram positive and gram negative?
Gram positive = blue
Gram negative = pink
Tetanus toxin
Exotoxins
Also called “lockjaw”
- Results in locked jaw
- Affects the central nervous system and interferes with transmission of impulses from the brain to muscles
Pyrogens
Endotoxins
- Cause fever, and life-threatening kidney damage
- Associated with hamburger disease,
What are the 3 elements required for transmission of infection?
1) Reservoir (source of infectious microbes)
2) Means of Transmission for the microbes
3) Susceptible host
What is the Chain Infection?
For an infection to occur, the elements of transmission must all occur. If the process is stopped, infection can be prevented
- We want to stop the chain at the transmission stage
What are the 3 types of reservoirs?
Human, animal, nonliving
Define: Human reservoirs
Principal reservoir of human infectious disease is the human body itself
- people with the disease & carriers
Define: Carriers
A person carrying potentially pathogenic microbes without any signs of disease or infection
Define: Chronic Carrier
A person who is a carrier for more than 6 months
What is a classic example of a carrier?
Typhoid Carrier
- Had typhoid and recovered but some of the typhoid bacteria remain in the body (often the gallbladder)
- Typhoid is transmitted by the ingestion of food contaminated with feces
Which diseases are transmitted by carriers?
Streptococcal sore throat, AIDS, Hepatitis B, and diphtheria
Define: Convalescent carrier
Once the person has recovered from the disease but may still be carrying infectious organisms
- A person carrying an infectious microbe for up to 6 months after the acute stage of the disease
Define: Zoonoses
Diseases that are primarily found in animals but may be transmitted to humans
Ex. Salmonella (eating improperly cooked poultry), rabies, and the plague
Define: Nonliving Reservoirs
Soil and water
- Botulism and Tetanus
- The spores responsible for both diseases are found in soil but simple contact with soil will not result in disease
Define: Botulism
A type of food poisoning and the spores must first grow in a food and produce toxin before the disease results
Define: Tetanus
Only results when spores are introduced into human tissue under conditions where there is little or no oxygen present
Bacteria grows in most moist environments
That’s why flowers are not allowed in some areas of the hospital
Diseases can be transmitted from the reservoir to the host by 3 principal routes, what are they?
Contact, Vehicle, and Vector
Define: Direct contact transmission
Direct physical contact between the reservoir and the host
- Person-to-person contact
- no intermediate object
- Transmitted by touching, kissing, and sexual intercourse
- Cold, flu, streptococcal sore throat and gonorrhea are transmitted this way
Define: Indirect contact transmission
Transferred from the reservoir to a nonliving object other then food(fomite) then to the host
- Transmitted through bedding, towels, utensils, toys, syringes and thermometers
- Hepatitis B and AIDS are transmitted this way
Define: Droplet transmission
Transmission in which the infectious microbes are contained in mucus droplets discharged from the respiratory tract of the reservoir
- travel one metre or less
- Colds, flu and whooping cough are spread this way
Define: Vehicle transmission
Transmission of infectious microbes by an agent such as food, water, air, blood or medication
- Typhoid and Cholera
- AIDS (by blood), Tuberculosis (by air)
How does air borne vehicle transmission travel?
Air borne transmission involves mucus droplets that travel further than one metre from the reservoir
- droplet nuclei stay in the air
- Tuberculosis
Define: Droplet nuclei
Tiny particles that remain suspended in the air often from dried respiratory secretions
Define: Vector transmission
Insects that carry infectious organisms from one host to another
- Malaria
Define: Host susceptibility. What is it influenced by?
Determines whether an encounter with an infectious microbe will result in disease
- Influenced by age, health, and immune status of the individual and the infectious dose
How can one become less susceptible to infection?
By receiving their vaccines and once they have had the particular infection, their body creates antibodies against that specific pathogen
What are the 4 portals of entry for Infectious Microorganisms?
1) Skin
2) Mucous Membranes
3) Placenta
4) Parenteral route
How can microorganisms enter by the skin?
- Through hair follicles or sweat glands
- Through excessively moist skin
- If the skin is broken or stitched up
How can microorganisms enter by the mucous membranes?
Through the portals of entry of the Respiratory(flu), Gastrointestinal(Hepatitis A) and Genital tracts(AIDS)
How can microorganisms enter by the placenta?
Only a very limited number of microorganisms that can cross the placenta barrier in the blood are rubella virus, Hepatitis B virus, and AIDS
How can microorganisms enter by the parenteral route?
It means the route that bypasses the GI tract (using an IV)
- Can also be entered by punctures, bites, cuts, surgical wounds and trauma injuries
What is the difference between a sign and a symptom?
Sign - Characteristic of a disease that can be observed by examining the patient (fever, redness, swelling)
Symptom - Characteristic of the disease that can be observed or felt only by the patient (pain, nausea, malaise)
How does your body indicate to you and infection?
Fever, lymph node swelling, and inflammation
Explain the sign of fever
Also called pyrexia
- Increase of 1 degree celcius above the normal body temperature (Normal= 36.1-37.8)
How is heat generated when you have a fever?
- Constriction of the blood vessels - Blood vessels dilate allowing blood to circulate close to the skin surface to lose heat (sweating)
- Increased metabolic rate (facilitates phagocytosis and tissue healing)
- Shivering
Pyrexia
Fever
Define: Lymphatic system
A series of vessels that drain fluid from tissues and return it to the blood stream. As the fluid moves along the lymphatic vessels, it passes through lymph nodes
Lymph node swelling may occur in infections as a result of:
- microbes from tissue fluid being trapped in a lymph node (multiplying and causing infection)
- Multiplication of lymphocytes responsible for immunity
Whats the difference between 1 swollen node? And multiple swollen nodes?
1 swollen node - indicates an infected node
Multiple - indicates the immune system responding to the microorganisms
What are the 3 sets of lymph nodes that can be felt?
Cervical nodes - in the neck
Axillary nodes - under the arms
Inguinal nodes - in the groin
What initiates the inflammatory response?
Histamine
What are the four cardinal signs and symptoms of inflammation?
Heat, Redness, Swelling and Pain
Histamine results in which two things?
1) Vasodilation - increasing blood flow to the injury site causing heat and redness
2) Increased permeability of the blood vessels - causing fluid to leak from the vessels into the surrounding tissues creating swelling and pain
How can histamine help the host clear the tissue of infecting microorganisms?
1) An increased number of phagocytic WBC are attracted to an area to engulf and destroy bacteria. They also present antigens to lymphocytes to activate antibody production
2) Antibodies are brought to the injury site. They coat the bacteria in preparation for phagocytosis or neutralize toxins
3) Clotting elements surround and isolate the microbes
Define: Purulent exudate
Results from the inflammatory response:
Pus (WBC). It represents phagocytic WBC that have been killed in action
* Purulent - containing WBC
Define: Leukocytosis
Results from the inflammatory response:
An increase in the number of WBC and the body’s response to the increased need for these cells
Define: Acute disease
A disease in which symptoms develop rapidly and the disease runs its course quickly
- measles, cold
Define: Chronic disease
A disease in which symptoms develop slowly and the disease is slow to disappear
- Tuberculosis
Define: Latent disease
A disease characterized by periods of inactivity either before symptoms appear or between attacks
- Herpes
Define: Localized infection
An infection confined to one area of the body. A streptococcal sore throat is a localized infection as long as the bacteria do not spread to other areas
Define: Focal infection
An infection confined to a specific area but pathogens from it, or their toxins, can migrate to other areas
- Abscessed tooth
Define: Systemic Infection
An infection in which the pathogen is spread to multiple organs or tissues of the body, often traveling via blood or lymph; also called disseminated infection
Define: Septicemia
The presence and multiplication of pathogens in blood
Define: Bacteremia
The presence but NOT multiplication of bacteria in the blood; they are merely in transit
- can turn into septicemia
Define: Viremia
The presence but NOT multiplication of viruses in blood, again just in transit.
- ex. Chicken pox - the virus enters the respiratory tract, transported to the skin and localized starting the rash
Define: Toxemia
The presence of toxins in the blood
Define: Exogenous infection
The microorganisms causing infection come from outside the host (another person, animal, environment)
Define: Endogenous infection
Microorganisms causing infection come from within the host’s body (normal flora organisms)
- Urinary infection - where the host’s own fecal bacteria find their way into the urinary system = infection
Define: Primary infection
Infection in a previously healthy individual
Define: Secondary infection
Immediately follows the primary infection; caused by a different microorganism. Fairly common
- Ex. pneumonia after having a viral influenza
Define: Nosocomial Infection
Infections acquired during a stay in a hospital or other health care facility
- acquired by 5-10% of patients
What are the three main factors contributing to nosocomial infections?
1) Hospital microorganisms (antibiotic resistant strains)
2) Compromised patients (already weak immune system)
3) Transmission (go from room to room)
What are the most common nosocomial infections? In order of occurence
1) Urinary tract infection (caused by E. coli when a patient had a bladder catheterization)
2) Surgical wound infections (cause by staphylococcus aureus introduced when the patient has an open wound- because 60% of staff are staph carriers)
3) Pneumonia (affects patients on a respiratory device)
What are antibiotic resistant bacteria?
Bacteria that were previously treatable with antibiotics but have now become resistant to that drug. Now they have to be treated with a different antibiotic that can be more harmful and costly
What are the two factors that have contributed to the development of drug-resistant bacteria?
1) Overprescription of antibiotics- when bacteria are continually faced with antibiotics, they become genetically tougher and resistant strains develop
2) When people quit taking their antibiotics when their symptoms fade but before all the bacteria are killed
How are drug resistant bacteria developed?
When the bacteria is treated with an antibiotic, most microbes are killed. But if there is one microbe that has a mutation and is resistant to the drug, then when the population grows back, they all grow back as drug resistant
What are the two types of drug resistant bacteria that are a major concern?
Methicillin-Resistant Staphylococcus aureus (MRSA) &
Vancomycin-Resistant Enterococcus (VRE)
What is Staphylococcus aureus? What is Methicillin-Resistant Staphylococcus aureus (MRSA)?
Staphylococcus aureus - causes infections - cellulitis, skin abscesses, and post-operative incision infections
- MRSA is resistant to Methicillin, spreads in hospitals
- Transmission by direct contact
How can we prevent MRSA from being spread? (4)
- Identify cases
- Isolate cases
- Identify carriers among patients and staff
- Eradicate MRSA from carriers (treatment with bactroban)
What is Vancomycin-Resistant Enterococcus (VRE)?
Enterococcus - Bacteria found as normal flora in the bowel
- Does NOT pose a threat to healthy individuals
- resistant to almost all drugs
- may be untreatable or fatal
- Transmission by direct contact or indirect contact through equipment
- Can survive up to 7 days on surfaces
- Testing involves culturing a rectal swab or stool specimen
Define: Epidemiology
Study of the incidence, sources and spread of disease
Define: Parenteral
Administrating something to the body by a route other than through the mouth… injections, punctures, etc.
