Define the following terms: infection, disease, infectious disease, pathogenic, virulence (virulent, (normavirulent), etiology, normal microbiota (normal flora), microbial antagonism, symbiosis (commensalism, mutualism, parasitism), and opportunists.
Infection - the growth of microorganisms in the body. Disease - an abnormal state in which part or all of the body is not properly adjusted or is incapable of performing normal functions; any change from a state of health. Infectious disease - a disease in which pathogens invade a susceptible host and carry out at least part of their life cycle in the host. Pathogenic - a disease-causing organisms. Virulence - the degree of pathogenicity of a microorganism. Etiology - the study of the cause of a disease. Normal microbiota - the microorganisms that colonize a host without causing disease; also called normal flora. Microbial antagonism - a property of microorganisms which enables one microorganism to kill, injure, or inhibit the growth of a different microorganism. Symbiosis - the living together of two different organisms or populations: commensalism - a symbiotic relationship in which two organisms live in association and one is benefited while the other is neither benefited nor harmed. mutualism - a type of symbiosis in which both organisms or populations are benefited. parasitism - a symbiotic relationship in which one organism (the parasite) exploits another (the host) without providing any benefit in return. Opportunists - an organism that exists harmlessly as part of the normal human body environment and does not become a health threat until the body's immune system fails.
Cite Koch's postulates.
I. the same pathogen must be present in every case of the disease.
II. the pathogen must be isolated from the diseased host in pure culture.
III. the pathogen must cause the same disease in a susceptible test animal.
IV. the pathogen must be re-isolated from test animal and documented as same organism.
Define the following terms: symptoms, signs syndrome, communicable disease, contagious disease, and noncommunicable disease
Symptoms - a change in body function that is felt by a patient as a result of a disease. Signs - a change due to a disease that a person can observe and measure. Syndrome - a specific that can be spread from one host to another. Contagious disease - a disease that is easily spread from one person to another. Noncommunicable disease - a disease that is not transmitted from one person to another.
Disease Occurrence: incidence (morbidity) vs. prevalence
Incidence - the fraction of the population that contracts a disease during a particular period of time. (morbidity) - the incidence of a specific disease and the condition of being diseased. Prevalence - the fraction of a population having a specific disease at a given time.
Epidemic - unusually large number of cases in short period of time.
Endemic - a disease present constantly in a community in relatively stable numbers.
Pandemic - an epidemic of world-wide occurrence.
Sporadic - a disease that occurs as occasional cases.
Define the following terms: acute disease, chronic disease, subacute disease, latent disease, herd immunity, local infection, systemic (generalized) infection, focal infection, bacteremia, septicemia, toxemia, viremia, primary infection and secondary infection, and inapparent or subclinical infection
Acute disease - a disease in which symptoms develop rapidly but last for only a short time. Chronic disease - a disease that is long-lasting or recurrent. Subacute disease - a disease with symptoms that are intermediate between acute and chronic. Latent disease - a disease characterized by a period of no symptoms when the pathogen is inactive. Herd immunity - the presence of immunity in most of a population. Local infection - an infection in which pathogens are limited to a small area of the body. Systemic (generalized) infection - an infection throughout the body. Focal infection - a systemic infection that began as an infection in one place. Bacteremia - a condition in which there are bacteria in the blood. Septicemia - the proliferation of pathogens in the blood, accompanied by fever; sometimes causes organ damage. Toxemia - the presence of toxins in the blood. Viremia - the presence of viruses in the blood. Primary infection - an acute infection that causes the initial illness. Secondary infection - an infection caused by opportunistic microbe after a primary infection has weakened the host's defense. Inapparent / Subclinical infection - an infection that does not cause a noticeable illness.
Predisposing factors for infectious disease: compromised host
age, genetic background, gender, pre-existing illness, nutrition, fatigue, lifestyle or occupation, chemotherapy, stress, and habits
Stages of Diseases:
1. Contact - contact with pathogen at successful portal of entry in sufficient numbers
2. Incubation - time between contact and onset of symptoms
3. Acute - period of illness and specific signs and symptoms
4. Decline - decline of signs and symptoms - crisis or lysis
5. Convalescence - period of recovery
Incubation and convalescence are particularly important in disease transmission because these periods often result in symptom-free carriers.
Reservoirs of infection: source of organism of infection (where?)
1. human - carriers either symptomatic or asymptomatic (AIDS, syphilis, Herpes, typhoid fever, hepatitis)
2. animals - domestic or wild zoonosis (anthrax, Rocky Mt. Spotted Fever, Lyme disease, rabies)
3. non-living - soil and water (ringworm, botulism, tetanus, Legionellosis)
Methods of Disease Transmission: (How?)
indirect contact - fomite transmission
droplet - short distance (influenza, whooping cough)
airborne - longer distances > 1 meter
tuberculosis, staphylococci, histoplasmosis
mechanical - passive transport
biological - active process - bites
infections acquired as a result of a hospital stay. 5-15% risk, approximately 2 million people in the US develop a nosocomial infection per year with nearly 90,000 deaths.
Three contributing factors:
a. microorganisms in the hospital environment
b. compromised hosts
c. chain of transmission
Define: emerging infectious diseases, epidemiology, and notifiable disease
Emerging infectious diseases (EID) - a new or changing disease that is increasing or has the potential to increase in incidence in the near future. Epidemiology - the science that studies when and where diseases occur and how they are transmitted. Notifiable infectious disease - a disease that physicians must report to the U.S. Public Health Service; also called reportable disease.
Cite the portals of entry for microbial infection
- Skin - (Mechanical) epithelial barrier keratin (Chemical) fatty acids in sebum, low pH low moisture, high salt, lysozyme, interferons.
- Respiratory Tract - (Mechanical) epithelial barrier mucus membrane cilia, hairs in nares coughing, sneezing (Chemical) lysozyme, salt in tears interferons
- Gastrointestinal Tract - (Mechanical) epithelial barrier mucus membranes peristalsis (Chemical) low pH, bile salts gastric juices, lysozyme interferons
- Genitourinary Tract - epithelial barrier mucus membranes urine flow, length of urethra and ureters cervical barrier, vaginal secretions (Chemical) low pH interferons
Transferrins are chemical iron-binding proteins found in the blood that inhibit bacterial growth by reducing the amount of available iron.
Contrast invasiveness and toxicity
Invasivness is the ability of microbe to colonize a tissuse while toxicity is the production of harmful substances such as endo toxin and exotoxins.
Explain how capsules, cell wall components, fimbriae, and enzymes contribute to the invasiveness of pathogens
The capsules of many pathogens, such as Streptococcus pneumoniae, resist the host defenses by impairing phagocytosis
cell wall components:can contribute to the bacteria's virulence. An example is the M protein on the fibrils of Streptococcus pyogenes, which helps it resist phagocytosis and improve adherence.
Extracellular Enzymes that some bacteria produce can digest material between cells, and help the bacteria spread into surrounding tissues.
Compare the effects of selected bacterial enzymes which act as virulence factors.
Contrast the nature and effects of exotoxins and endotoxins.
Exotoxins - poisons produced by microorganisms and released in the environment.
2. most produced by Gram + bacteria with a prophage or on a plasmid
3. usually heat sensitive
4. highly toxic, specific in action A-B toxins - diphtheria, botulism. Membrane - disrupting toxins. Hemolysins, leucocidins. Superantigens - Staph. Enteroxin
5. strongly antigenic immunize with toxoid
6. treat sever cases with antitoxins
Examples: Exotoxins can also be classified by action, Neurotoxin - botulism, Enterotoxins - E. Coli and Staph., Cytotoxins - diphtheria
Endotoxins - poisons that are an integral part of the cell wall - released in significant amounts only upon lysis of the cell.
1. lipid A of the LPS
2. cell wall component of Gram - cells
3. heat resistant
4. non-specific generalized action fever, weakness aches, shock, intravascular clotting
5. weak antigen - antibodies are nonprotective no toxoid
6. no antitoxin - drug "Zovan" counteracts clotting and inflammation
Examples: meningococcal meningitis, typhoid fever
Define innate immunity
All the bodys defenses that protect the body against any kind of pathogens
Describe the mechanical, chemical and cellular factors that act as nonspecific host defenses at the skin, respiratory tract and GU tract.
Mechanical factors: Epithelial barrier, keratin
Chemical: Fatty acids in sebum, low pH, low moisture, high salt, lysozyme ,interferons
Mechanical Factors:Epithelial barrier, mucus membrane, cilia, hairs in nares, coughing, sneezing
Chemical:Lysozyme,salt in tears, interferons
Mechanical factors: Epithelial barrier,mucus membrane,peristalsis
Chemical Factors: low pH, bilesalts, gastric juices, lysozyme, interferons
Mechanical: Epithelial barrier,mucus membranes, urine flow, length of urethra and ureters,cervical barrier, vaginal secretions
Chemical Factors: Low pH, Interferons
Describe the stages of phagocytosis
1.chemotaxis:phagocytic cells are attracted to infection sites
2. phagocytosis:adherence binds the cell membrane of the phagocytic cell to the microbe.
Classify the five types of leukocytes and describe their function as it relates to immunity.
Describe the signs of inflammation and the events that lead to inflammation as well as the benefits and potential harm to the host.
Inflammation is the second line of defense.
Inflammation begins with an injury. It can also be triggered by excessive heat or harsh chemicals.
There are three stages of inflammation-vasodilation, phagocyte movement, and tissue repair.
First, damaged tissue releases chemical signals causing vasodilation, or blood vessel widening. Next, the chemical signals attract phagocytes, which actively engulf and kill microbes through phagocytosis. Finally, tissue repair occurs.
Discuss the role of fever in nonspecific resistance.
Fever is an abnormally high body temperature produced in response to bacterial or viral infection. This could cause brain damage.
Shivering:muscles trying to contract to raise body temp.
Sweating(Crisis): indicates the body temperature is falling
Chill: indicates a rising body temp
Discuss the composition, synthesis, and action of interferons.
Interferons are antiviral proteins produced in response to viral infection.Interfere with the replication of viruses and other pathogens.
There are three types of interferon - alpha, beta, and gamma. Alpha and beta interferons are produced by cells infected with viruses to produce antiviral proteins (AVPs) that prevent viral replication.
Interferons are host cell specific but not virus specific
Gamma interferons activates neutrophils and macrophages to kill bacteria.
Discuss the composition, activation, and functions of the complement system.
Complement system consists of a group of serum proteins that activate one another to destroy invading micoorganisms.
There are three pathways for complement activation. The complement proteins are activated in a cascade.
1.Classical pathway:Immune reaction of an anitibody and antigen, it requires specific antibodies, such as antibodies that bind a bacterium. Antibody production occurs in adaptive immunity .
2.Alternative pathway:Direct interaction with cerain proteins in the cell.
3: Lectin pathway: