MICROBIOLOGY UNIT 4 EXAM
Distinguish between mechanical and biological vectors. Give examples.
*biological vector* - an animal vector in whose body the pathogenic organism develops and multiplies before being transmitted to the next host. - Biological vectors harbor pathogens within their bodies and deliver pathogens to new hosts in an active manner, usually a bite. (ex. arthropods - ticks, mosquitoes, fleas) *mechanical vector* - an animal vector not essential to the life cycle of the parasite. - A mechanical vector picks up an infectious agent on the outside of its body and transmits it in a passive manner, meaning the mechanical vector is not infected by the pathogenic organism. (ex. foot of an arthropod carries pathogen)
List the principle cells in Cell-mediated immunity and give the main function of each.
- Does NOT involve antibodies. = Immune response involving activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. 1. Activating antigen-specific cytotoxic T-lymphocytes (CTLs) that are able to destroy body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens; 2. Activating macrophages and NK cells, enabling them to destroy intracellular pathogens; and 3. Stimulating cells to secrete a variety of cytokines that influence the function of other cells involved in adaptive immune responses and innate immune responses.
Explain the term immunity. Compare active immunity with passive immunity.
- Immunity: the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells. - active immunity: results from the production of antibodies by the immune system in response to the presence of an antigen. - passive immunity: the short-term immunity which results from the introduction of antibodies from another person or animal.
Distinguish between normal flora and transient flora.
- Normal (resident) flora: microorganisms including bacteria, protozoa, and fungi that are found on or in specific areas of the body ~commonly~ (in some instances, resident flora may cause issues in some cases like overcolonization). - Transient flora: episodic microorganisms including bacteria, protozoa, and fungi which are "foreign" to the typical flora -- some transient microbes cause issues (pathogens).
Distinguish between localized and systemic infections.
- Systemic means affecting the entire body, rather than a single organ or body part. (ex. an infection that is in the bloodstream is called a *systemic infection*). An infection that affects only one body part or organ is called a *localized infection*. -- many infections start locally and become systemic
Explain the process of antibody formation. Include the primary response and secondary response.
- The presence of an antigen (foreign protein) in the body triggers the formation of antibodies, which (are formed by B lymphocytes) work against these foreign proteins to neutralize/combat the foreign substance. - When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone. Primary immune response: occurs the first time that a pathogen is encountered - detectable concentrations of antibodies in 5-10 days Secondary immune response: occurs after the first time that a pathogen is encountered (2nd, 3rd, 4th, etc.) - Results from memory cells - Detectable concentrations of antibodies in 1-2 days
Explain phenomenon called "microbial antagonism".
- Usage of established microorganismic cultures to inhibit/prevent the intrusion of other species which seek to invade the environment.
Explain how infectious agents enter the following: a) skin, b) gastrointestinal tract, c) respiratory tract, d) Urogenital tract, e) placental entry
- skin - a cut or wound - gastrointestinal tract - improper/incomplete chewing of foods might allow pathogens to make it past the stomach's acidity - respiratory tract - air quality; airborne pathogens of various kinds (ex. air droplets from sneezing -- aerosol) can travel through the air - urogenital tract - contaminated catheter; improper perineal care - placental entry - Infectious agents can reach the placenta either via maternal blood or by ascending the genital tract
Explain what 'etiology' means.
- the study of causation: the cause, set of causes, or manner of causation of a disease or condition.
Explain what a vaccine is. Relate the secondary response to booster shots and rejection reaction.
- vaccine: a substance which stimulates the production of antibodies and provides active, acquired immunity to a particular disease by using a preparation made from the causative agent of the disease, its products, or a synthetic substitute which acts as an antigen without inducing disease During subsequent exposures to the same pathogen, the immune system is able to respond rapidly and activity reaches higher levels. The secondary immune responses can usually prevent disease, because the pathogen is detected, attacked and destroyed before symptoms appear. - Memory of the infection is reinforced and long lived antibodies remain in circulation. Rejection reactions are adverse and seldomly occur; many adverse effects may occur due to coincidence and not by the vaccine. = However, individuals who have serious immunodeficiencies are clearly at increased risk for specific adverse reactions to live viral vaccines, such as MMR and varicella vaccines.
Compare the size of viruses to red blood cells.
- viruses range in size from about 20 to 400 nanometres in diameter (1 nanometre = 10-9 meters) whereas - red blood cells (from humans, particularly) have a disk diameter of approximately 6.2-10 µm and a thickness at the thickest point of 2-2.5 µm and a minimum thickness in the centre of 0.8-1 µm, being much smaller than most other human cells.
Describe multiplication cycles in animal viruses.
1. Attachment: Viruses attach to cell membrane 2. Penetration by endocytosis or fusion 3. Uncoating by viral or host enzymes 4. Biosynthesis: Production of nucleic acid and proteins 5. Maturation: Nucleic acid and capsid proteins assemble Release by budding (enveloped viruses) or rupture
Describe the various ways in which antibiotics exert their action.
1. Inhibition of Cell Wall Synthesis (most common mechanism) [ex. Beta-Lactams ---> Inhibition of peptidoglycan synthesis (bactericidal)] 2. Inhibition of Protein Synthesis (Translation) - Ribosomal (second largest class) [ex. Tetracyclines ---> Block tRNA binding to 30S ribosome-mRNA complex (b-static)] 3. Alteration of Cell Membranes [ex. Bacitracin (topical) ---> Disrupt cytoplasmic membranes] 4. Inhibition of Nucleic Acid Synthesis (with DNA or RNA effects) [ex. DNA ---> Metronidazole ---> Metabolic cytotoxic byproducts disrupt DNA] 5. Antimetabolite Activity [ex. Sulfonamides such as SULFANILAMIDE ---> Compete with p-aminobenzoic acid (PABA) preventing synthesis of folic acid]
Describe, in general, the disk diffusion method for determination or susceptibility to chemotherapeutic drugs.
1. Using a sterile cotton tip applicator, aseptically transfer a broth culture of a given organism; create a bacterial lawn. 2. Streak the Mueller-Hinton agar from all directions and allow the plate to dry for ~5 minutes. 3. Apply antibiotic discs (or chemotherapeutics) with the disk dispenser. 4. Flame the forceps and gently press each disc to ensure it is secure within the agar. 5. Incubate for 24 hours at 35°C. Observe for after incubation, looking at the zones of inhibition. This gauges the susceptibility of the microorganism to the antibiotic/chemotherapeutic agent.
Know what Acquired Immune Deficiency Syndrome is.
Acquired immunodeficiency syndrome (AIDS) is a chronic, life-threatening condition caused by the human immunodeficiency virus (HIV). - Attacks the body's immune system, specifically the CD4 cells, often called T cells. Over time, HIV can destroy so many of these cells that the body can't fight off infections and disease.
Explain what is meant by being a "carrier" of infectious disease.
An asymptomatic carrier (healthy carrier or just carrier) is a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms. Although unaffected by the pathogen, carriers can transmit it to others or develop symptoms in later stages of the disease. -- these carriers have furthered the spread of infectious diseases, similar to the 80-20 rule in epidemiology which states 20% of the population conducts the disease transmission in a population
Explain what anaphylactic shock is.
Anaphylaxis is a severe, whole-body allergic reaction to a chemical that has become an allergen. An allergen is a substance that can cause an allergic reaction. -- Sensitivity of one's immune system to a particular stimuli.
Know the general structure of an antibody, and how they function.
Antibodies are immune system-related proteins called immunoglobulins. Each antibody consists of four polypeptides- two heavy chains and two light chains joined to form a "Y" shaped molecule. The amino acid sequence in the tips of the "Y" varies greatly among different antibodies. This variable region, composed of 110-130 amino acids, give the antibody its specificity for binding antigen. The variable region includes the ends of the light and heavy chains.
Relate antibody action with allergies.
Antibodies are present whenever antigens provoke an immune reaction in the test serum. Allergic reactions are triggered when allergens cross-link preformed IgE bound to the high-affinity receptor FcεRI on mast cells. Mast cells line the body surfaces and serve to alert the immune system to local infection. Once activated, they induce inflammatory reactions by secreting chemical mediators stored in preformed granules, and by synthesizing leukotrienes and cytokines after activation occurs. In allergy, they provoke very unpleasant reactions to innocuous antigens that are not associated with invading pathogens that need to be expelled.
What is it meant by a "good antigen?"
Antigens that elicit strong immune responses are said to be strongly immunogenic. ~ For example, bacteria which are capsulated are not ideal as polysaccharides are not highly antigenic. Antigenicity is the specific measure of the antibody response toa specific target antigen. The potency of the antigen is defined by the composition and structures of the antigen that are exposed to the antibody, specifically the complementary determining regions that define the paratope of the antibody.
Know what autoimmunity is and give examples.
Autoimmunity is the system of immune responses of an organism AGAINST its own healthy cells and tissues. -- results from an autoimmune disorder Examples include: irritable bowel syndrome (IBS), Lupus, alopecia areata, Celiac disease, and ankylosing spondylitis.
Explain what LD50 and ID50 stand for.
BOTH ARE MEASURES OF VIRULENCE. - LD50 refers to "Lethal Dose, 50%" -- the amount of a given "substance" (per body weight, typically) which causes elimination of 50% of the test population. ID50 refers to "Infectious Dose, 50%" -- the amount or number of microbes necessary to infect a hose in 50% of the test population.
Distinguish between communicable and non-communicable diseases.
Communicable, or infectious diseases, are caused by microorganisms such as bacteria, viruses, parasites and fungi that can be spread, directly or indirectly, from one person to another. --- caused by agent! (ex. HIV/AIDS, MRSA, tuberculosis, etc.) A non-communicable disease (NCD) is a disease that is not transmissible directly from one person to another. (ex. autism, osteoporosis, Celiac disease, etc.)
Define and describe: Disease, Pathogen, Infection, Virulence, and Resistance.
Disease: a disorder of structure or function, especially one that produces symptoms or affects a specific location. Pathogen: a bacterium, virus, or other microorganism that can cause disease. Infection: the process of infecting or the state of being infected. Virulence: a pathogen's or microbe's ability to infect or damage a host (specifically the degree of pathology caused) Resistance: in the instance of antibiotic resistance, the term refers to the ability of bacteria and other microorganisms to resist the effects of an antibiotic to which they were once sensitive
Distinguish between endemic, epidemic, and pandemic diseases.
Endemic: a disease that exists permanently in a particular region or population. Malaria is a constant worry in parts of Africa. Epidemic: An outbreak of disease that attacks many peoples at about the same time and may spread through one or several communities. Pandemic: When an epidemic spreads throughout the world.
Explain what an immunodeficient disease is.
Immunodeficiency is a state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") due to extrinsic factors that affect the patient's immune system.
What is the extent (epidemiology) of host involvement or rather, what do we use to gauge epidemiology (study of incidence, distribution, and possible control of diseases and other factors relating to health)?
Incidence: fraction of population that contracts a disease during a specific time Prevalence: fraction of a population having specific diseases (which are prevalent) at a given time
Explain what is meant by first, second, and third lines of defense.
Innate (Nonspecific Immunity) Defenses: - 1st line (passive): skin, mucous membranes, secretions of skin and mucous membranes, and antagonism of residing normal microbiota - 2nd line (active): phagocytic leukocytes, antimicrobial proteins, fever, and inflammatory response Acquired (Specific/Adapted Immunity) Defenses: - 3rd line (active): lymphocytes and antibodies
Describe and define the following terms: Sterilization, Disinfection, Chemotherapy, and Antisepsis.
Sterilization: refers to any process which eliminates, removes, kills, or deactivates all forms of life including biological agents Disinfection: antimicrobial agent applied to surfaces/objects to destroy microorganisms -- less effective than sterilization & doesn't kill all bacteria and spores Antisepsis: usage of antiseptic to eliminate/reduce microorganisms that cause infection and disease (some are only bacteriostatic, which means that growth is merely prevented/inhibited) Chemotherapy: In microbiology, this refers to the clinical application of antimicrobial agents to treat infectious disease.
Describe the 5 parts of the multiplication cycle in bacteriophages.
The lytic cycle is one of the two cycles of viral reproduction, the other being the lysogenic cycle. These cycles should not be seen as separate; they should rather be seen as two parts of viral reproduction. The lytic cycle is typically considered the main method of viral replication since it results in the destruction of the infected cell and the release of new viruses. *Lytic Cycle:* 1. Attachment: phage attaches to host cell 2. Penetration: phage penetrates host cell and injects its DNA 3. Biosynthesis: production of phage DNA and proteins (viral DNA uses host ribosomes "host RNA polymerase" which elicits response where bacterial DNA gets destroyed -- dissolving cellular proteins) 4. Maturation: viral components are assembled into virions 5. Release: host cell lyses and new virions are released. ~ From there, new bacterial cells are searched for within the medium and injected with the phage DNA -- a continuous process. *Lysogenic (incorporation) Cycle:* 1. Adsorption 2. Entry 3. Integration: formation of provirus or prophage by inserting viral DNA into host genome 4. Spontaneous induction: release of viral DNA from host genome 5. Replication 6. Assembly 7. Lysis & Release
Describe the structure of the covering and the central core of viruses (virion).
There is the covering (viral envelope) and central core. - In the covering, there is a capsid (made of capsomere proteins) and a glycoprotein envelope. - In the central core there is nucleic acid (DNA or RNA) and matrix proteins enzymes.
Explain why viral diseases are more difficult to treat than bacterial diseases.
Viruses are hard to treat because they are a hundred times smaller than human cells. Furthermore, they use these very cells to stay protected from antibiotic medication, which travels through the bloodstream. Additionally, the viral envelope, which is the external coating on the virus, is almost exactly like the membranes of the host cell. This makes it even harder to identify and differentiate between the two.
Explain the process of inflammation.
When a bacterial infection is established in the body, the purpose of the immune system is to control or eradicate it. The initial reaction of the immune system to an infection varies, depending on the site which has been invaded and on the nature of the invader. Vasodilation: leads to greater blood flow to the area of inflammation, resulting in redness and heat. Vascular permeability: endothelial cells become "leaky" from either direct endothelial cell injury or via chemical mediators. Exudation: fluid, proteins, red blood cells, and white blood cells escape from the intravascular space as a result of increased osmotic pressure extravascularly and increased hydrostatic pressure intravascularly Vascular stasis: slowing of the blood in the bloodstream with vasodilation and fluid exudation to allow chemical mediators and inflammatory cells to collect and respond to the stimulus.
Explain what zoonoses are and give examples.
Zoonoses (also known as zoonotic diseases) are infectious diseases caused by bacteria, viruses and parasites that spread between animals (usually vertebrates) and humans. - Examples include: rabies, MRSA, enterocltica, salmonella, Campylobacter, etc.
Know what is meant by antimicrobial drugs, and some examples.
antimicrobial drug: a drug which is used to treat a microbial infection -- a broad term INCLUDING antibiotics, antifungals, antiprotozoals, and antivirals. ~ examples ~ antibacterial: azithromycin (Zithromax) antifungal: miconazole antiviral: oseltamivir (Tamiflu) antiparasitic: mebendazole (Emverm)
Compare commensalism, mutualism, and parasitism.
commensalism: an association between two organisms in which one benefits and the other derives neither benefit nor harm. mutualism: symbiosis that is beneficial to both organisms involved -- mutually beneficial for both parties. parasitism: relationship between two organisms in which one benefits at the expense of the other (with or without killing the host organism).
Describe how agents of disease can be transmitted by theses routes: a) contact transmission, b) common vehicle transmission, c) airborne transmission, d) vectors.
common vehicle transmission - transmission by an inanimate reservoir (food, water, wind). *biggest concern as of today* vectors - arthropods (fleas, ticks, mosquitoes) inserted ~usually hypodermically~ - pathogens usually reproduce in vector mechanical - arthropod carries pathogen on feet
Explain what is meant by cytopathic effects.
cytopathic - pertaining to producing damage in living cells = cytopathic effect refers to structural changes in host cells resulting from viral invasion The infecting virus causes lysis of the host cell or when the cell dies without lysis due to an inability to reproduce.
Compare a disinfectant with an antiseptic, along with other chemical means of control discussed in class.
disinfectant - antimicrobial agent applied to surface of object to destroy living microorganisms, not always killing all microorganisms (especially resistant spores) - less effective than sterilization (100%) antiseptic - antimicrobial agents applied to living tissue/skin to reduce infection, sepsis, etc. - An antiseptic is applied to the body, while disinfectants are applied to nonliving surfaces, such as countertops and handrails. -- both contain agents called biocides, but antiseptics usually contain lower concentrations of biocides than disinfectants
Distinguish between inactivated and attenuated vaccines.
inactivated vaccine: a vaccine consisting of virus particles, bacteria, or other pathogens that have been grown in culture and then killed. attenuated vaccine: a vaccine created by reducing the virulence of a pathogen, but still keeping it viable (or "live").
Compare the lytic cycle with the lysogenic cycle.
lysogenic cycle - prophage DNA incorporated in host DNA lytic cycle - phage causes lysis and death of host cell
Describe these nonspecific host defense mechanisms: Mechanical, Chemical, Phagocytosis.
mechanical: This body defense mechanism include certain structures and functions of the body. Example: skin, hairs, mucous membranes, coughing, sneezing, tear glands, urinating chemical: this body defense mechanism has some barriers that help protect from pathogens. Examples: sebaceous glands, fluids in stomach, interferons, lysozyme (in tears/saliva) phagocytosis (condition of an engulfing cell): Phagocytosis is a nonspecific defense mechanism in which various phagocytes engulf and destroy the microorganisms of disease. Phagocytes. Among the important phagocytes are the circulating white blood cells called neutrophils and monocytes.
Discuss why viruses are not considered to be living.
~ not a cell ~ - living things must maintain homeostasis - living things grow independently - living things respond to stimuli - contain DNA OR RNA (not both) - instead of a phospholipid bilayer, the outside is composed of a protein coat (or an envelope)
