Unit 2 - Topic 2: Infectious Diseases & Epidemiology

What distinguishes infectious diseases from non-infectious diseases?

Infectious diseases are caused by pathogens and can be transmitted between individuals, while non-infectious diseases are not caused by pathogens and cannot be spread.

What are the causes of non-infectious diseases?

Non-infectious diseases are caused by genetic, environmental, and lifestyle factors.

Provide an example of an infectious disease and a non-infectious disease.

An example of an infectious disease is influenza, while an example of a non-infectious disease is cancer.

Why can a person experience influenza more than once in a single flu season?

Different strains of the influenza virus circulate each year, and the virus can mutate, creating new variants that the immune system may not recognize.

What structural feature of a tapeworm helps it survive in its host?

The tough, protective layer called the tegument shields the tapeworm from the host's digestive enzymes and acids.

How do invasion factors increase the virulence of a pathogen?

Invasion factors enable a pathogen to multiply within a host, overcome host defenses, and cause disease.

How do immune cells recognize self from non-self?

Immune cells have receptors for self-antigens and non-self-antigens, allowing them to determine the type of threat posed by other cells.

What are the three lines of defense in vertebrates?

1. Innate immune response: skin and mucous membranes (non-specific) 2. Inflammatory response and complement system (non-specific) 3. Adaptive immune response (specific).

What is the first line of defense in the innate immune response?

The first line of defense includes physical and chemical barriers like skin, mucus, tears, and stomach acid that block pathogens from entering.

What is the second line of defense in the innate immune response?

The second line of defense involves internal immune responses such as inflammation, phagocytosis by white blood cells, and fever.

What role does the complement system play in the immune response?

The complement system consists of proteins in the blood that help destroy pathogens by marking them for attack or puncturing holes in their membranes.

What would you expect from B-lymphocytes when injected with two different antigens?

Each B-lymphocyte produces only one specific antibody that matches a single antigen, so individual plasma cells would produce antibodies for only one of the two antigens.

Justify the prediction about B-lymphocytes producing antibodies.

The immune system is designed such that each B-lymphocyte is specific to one antigen, ensuring that it produces antibodies only for that particular antigen.

What do B-cells generate during development?

Unique receptors by randomly rearranging gene segments.

What happens when B-cells encounter their specific antigen?

They become activated and differentiate into antibody-producing plasma cells.

Describe the role of prostaglandins in the inflammatory response.

They promote vasodilation, which increases blood flow to the affected area.

What are the roles of neutrophils and macrophages in the inflammatory response?

They engulf pathogens and release chemicals that contribute to inflammation.

What type of immune cell is involved in allergic reactions?

Mast cell.

What do structures X and Y represent in the diagram of the immune cell?

Structure X represents antibodies bound to receptors on the mast cell surface; Structure Y represents vesicles containing chemicals released during allergic responses.

What occurs in the region around an embedded piece of wood that causes an inflammatory response?

Blood vessels dilate, allowing immune cells to enter the tissue, leading to redness, swelling, heat, and pain.

What triggers the red patches and blisters on Paul after encountering poison ivy?

His immune system recognized the poison as harmful, triggering a delayed hypersensitivity reaction.

Why was Paul instructed to wash thoroughly after exposure to poison ivy?

To remove any remaining oils that can cause further irritation and prevent spreading to other areas or people.

What is the purpose of wearing long pants and sleeves after a poison ivy reaction?

To prevent skin contact with poison ivy or other irritants and reduce the chance of another allergic reaction.

What is immunity?

The body's ability to resist infection and fight off harmful pathogens.

Which branch of immunity responds differently to specific antigens and can form memory?

The adaptive immune system.

What are the key differences between humoral and cell-mediated immunity?

Humoral immunity involves B-cells producing antibodies targeting pathogens in body fluids; cell-mediated immunity involves T-cells attacking infected or abnormal cells.

What is the role of Memory B-cells in providing lifelong immunity?

They remember past infections and enable a quicker and stronger response upon re-exposure to the same pathogen.

What is the significance of the yellow fever vaccine?

It provides lifelong immunity against a potentially fatal viral disease.

What type of immunity does the adaptive immune system provide?

Long-term protection after exposure to a pathogen.

What is the function of T-lymphocytes in the adaptive immune response?

They attack infected cells directly.

What is the role of antibodies in the humoral immune response?

They target and neutralize pathogens in body fluids.

How do neutrophils contribute to the inflammatory response?

They are among the first immune cells to arrive at the site of infection and help engulf pathogens.

What is the primary function of natural killer cells?

They destroy infected or cancerous cells.

What causes redness and swelling during an inflammatory response?

Increased blood flow and the accumulation of immune cells in the affected area.

What is the outcome of a delayed hypersensitivity reaction?

Inflammation and symptoms such as redness, itching, and blistering.

Why is it important to cut nails short after exposure to poison ivy?

To prevent scratching and spreading the oil further.

What is the role of macrophages in the immune response?

They engulf and digest pathogens and dead cells, and also help activate other immune cells.

What is the role of memory B-cells in the immune response?

They remember and quickly produce specific antibodies if the virus is encountered again.

How do memory T-cells function during future infections?

They recognize infected cells and help destroy them faster, preventing illness.

What conclusion can be drawn from the graph showing antibody levels after two exposures to the same pathogen?

After the first exposure, antibody levels rise slowly and then decline; after the second exposure, the response is faster and stronger with a higher peak in antibody concentration.

What are the two types of immune responses measured in vaccine trials for EVD?

Humoral response and cell-mediated response.

How does humoral immunity differ from cell-mediated immunity?

Humoral immunity involves B-cells producing antibodies in body fluids, while cell-mediated immunity involves T-cells attacking and destroying infected cells directly.

What is the cell-mediated response to an infectious disease?

It involves T-cells recognizing foreign antigens on infected cells, activating cytotoxic T-cells that bind to and destroy those infected cells.

What prediction can be made about B-lymphocytes when injected with two different antigens?

Each B-lymphocyte will produce antibodies specific to only one antigen, either antigen A or antigen B, due to clonal selection.

What type of immunity is acquired when a person receives an injection of specific antibodies after a rabies bite?

Passive immunity, as the person receives already made antibodies.

Why is passive immunity considered temporary?

Because no memory cells are formed, providing immediate protection but not long-lasting.

Is childhood immunization an active or passive form of protection?

Active immunity, as the child's immune system is stimulated to produce memory cells and antibodies in response to the vaccine.

What is the purpose of booster injections in immunization schedules?

Booster injections remind the immune system by re-exposing it to the antigen, increasing the number of memory cells and antibody levels for stronger immunity.

What type of immunity does a baby acquire from a measles, mumps, and rubella vaccination at 12 months?

Active immunity, as the vaccine stimulates the baby's immune system to produce antibodies and memory cells.

What type of immunity is present when antibodies are passed from a mother to her baby during breastfeeding?

Passive natural immunity, as the baby receives ready-made antibodies through breast milk.

What is the role of antibodies passed from mother to infant before birth?

They help protect the baby from infections, but the immunity is temporary.

What happens to T-cell counts in an untreated HIV patient over time?

The number of T-cells steadily declines due to HIV targeting and destroying these cells, leading to a weakened immune system.

At what point does the T-cell count fall below critical levels in HIV patients?

During the AIDS phase, when the immune system is severely weakened.

When are maternal IgG antibodies no longer detectable in an infant?

About 6 months after birth.

When does a newborn infant have the greatest chance of infection by bacteria?

The greatest chance of infection occurs when maternal antibodies decline and the infant's immune system is still developing.

How does immunity acquisition change from prior to birth to 12 months after birth?

Prior to birth, the infant relies on maternal antibodies; after birth, the infant begins producing its own antibodies while still receiving some from breast milk.

What is a physical method of defense in plants?

The waxy cuticle, which covers leaves and stems, preventing pathogen entry and reducing water loss.

Name two chemical barriers that plants use to protect against pathogens.

Resins that trap pathogens and seal wounds, and enzymes that break down fungal cell walls.

What are two ways humans prevent pathogens from entering the internal environment?

The skin and stomach acids.

What is the effect of HIV on T-cell counts during primary infection?

There is a sharp decrease in T-cells.

What is the significance of T-cells in the immune response?

T-cells are essential for coordinating the immune response.

What happens to T-cells after the initial decline in an untreated HIV patient?

T-cells partially recover, but the virus remains active and slowly increases.

What is the role of IgG antibodies in infants?

IgG antibodies are active against viruses and some bacteria and can cross the placenta.

What is the role of IgA antibodies in infants?

IgA antibodies are present in saliva and tears and help protect mucosal surfaces.

What is the role of IgM antibodies?

IgM antibodies are active against some bacteria but do not cross the placenta.

What is a chemical defense strategy used by plants?

Plants produce toxins that deter herbivores and pathogens.

How do leaf hairs contribute to a plant's defense?

Leaf hairs can deter insects and reduce water loss.

What happens to the levels of maternal antibodies after birth?

Maternal antibodies decline after birth as the infant begins to produce its own antibodies.

What is the role of thorns in plant defense?

Thorns act as a physical barrier to deter herbivores.

What is the importance of the waxy cuticle in plants?

It acts as a shield against pathogens and helps maintain water balance.

How do enzymes in plants protect against pathogens?

They break down the cell walls of fungi, preventing infection.

What is the relationship between maternal antibodies and infant immunity?

Maternal antibodies provide temporary immunity until the infant's immune system develops.

What is the significance of the decline in maternal IgG levels?

It indicates the transition to the infant's own immune response development.

What is the most effective antibiotic based on the zones of inhibition in the experiment?

ATB3, as it has the largest zone of inhibition, indicating it was most successful at preventing E. coli growth.

What does a larger zone of inhibition indicate about an antibiotic's effectiveness?

It indicates that the antibiotic is more successful at killing or stopping bacterial multiplication.

What method is used to test the effectiveness of antibiotics on bacteria?

The disc method, which involves impregnating a filter paper disc with a substance and placing it on an agar plate inoculated with bacteria.

What indicates that bacterial growth is inhibited in the disc method?

A clear zone around the disc where there has been little to no growth after 48 hours.

What is the average zone of inhibition for penicillin action on Bacillus subtilis?

4 mm, calculated from the trials.

How does the standard error of the zone of inhibition for E. coli compare to that of Staphylococcus aureus?

E. coli has a lower standard error (2.1 mm) than S. aureus (2.6 mm), indicating a more precise mean estimation.

What does a zone of inhibition greater than 13 mm indicate about bacterial susceptibility?

The bacteria is considered sensitive to the antimicrobial substance.

What does a zone of inhibition of 0 mm indicate about bacterial susceptibility?

The bacteria is considered resistant to the antimicrobial substance.

Which bacterial species showed the highest resistance to penicillin?

Staphylococcus aureus, with a resistance rating of +++.

What alternative substance could be developed into an antibiotic for golden staph?

An alternative substance could be Doxycycline, as it shows effectiveness against S. aureus.

What is the significance of the clear zone around an antimicrobial disk?

It signifies that the antimicrobial substance is effective in inhibiting bacterial growth.

How many new substances isolated from Australian fungal species are being tested for antimicrobial properties?

Six new substances.

What does the term 'intermediate response' refer to in the context of bacterial susceptibility?

A zone of inhibition between greater than 0 mm and less than or equal to 13 mm.

What is the purpose of measuring the zone of inhibition in antimicrobial testing?

To determine the effectiveness of different antimicrobial substances against bacterial growth.

What does a resistance rating of +++ indicate?

It indicates the highest level of resistance to the tested substance.

What was the zone of inhibition for Escherichia coli in Trial 1 for penicillin?

19 mm.

What is the average zone of inhibition for penicillin on Escherichia coli across three trials?

21 mm.

What is the relationship between the size of the zone of inhibition and the effectiveness of an antimicrobial substance?

Larger zones indicate greater effectiveness in inhibiting bacterial growth.

What is the significance of the statistical analysis in comparing E. coli and S. aureus results?

It helps determine which bacterial species is more susceptible to the antibiotic based on mean and standard error.

What does the presence of a zone of inhibition suggest about a new antimicrobial substance?

It suggests that the substance may have potential as an antibiotic.

What is the role of microbiologists in the context of antibiotic resistance?

They experiment with new substances that may have antimicrobial properties to combat resistant bacteria.

What is the main focus of the experiment described in the student's notes?

Investigating the effectiveness of different antimicrobial substances in reducing or preventing bacterial growth.

What is the significance of the average zone of inhibition in evaluating antibiotic effectiveness?

It provides a quantitative measure to compare the effectiveness of different antibiotics against specific bacteria.

What is the zone of inhibition for Chloramphenicol?

16 mm

What is the sensitivity classification for Penicillin?

Sensitive to

What does a zone of inhibition of 0 mm indicate for Sulphatriad?

Resistant to

What is the zone of inhibition for Tetracycline?

9 mm, classified as Intermediate.