Microbiology Final

What is the purpose of clonal selection and what is the process?

The purpose of clonal selection is to selectively proliferate a specific lymphocyte that can fight a unique invading pathogen. When a B or T cell encounters its matching antigen, it is activated to rapidly divide and create a large army of identical clones to fight the infection.

What is an antigen and what cells process and present antigens?

An antigen is any foreign substance (like a protein or polysaccharide) that triggers an immune response. Specialized immune cells—specifically dendritic cells, macrophages, and B cells—engulf, process, and present these antigens on their surface to activate other immune cells.

What is tolerance and what are two mechanisms that prevent us from reacting to

self?

Tolerance is the immune system's ability to recognize and avoid attacking the body's own healthy tissues. Two key mechanisms that prevent self-reactivity are central tolerance (deleting autoreactive cells during development) and peripheral tolerance (silencing or suppressing any self-reactive cells that escape into the body).

What are two key advantages of an acquired immune response compared to drugs?

An acquired immune response offers lifelong immunological memory, meaning it can rapidly destroy a returning pathogen before you get sick, whereas drugs only provide temporary treatment. Additionally, the immune response is highly specific and adaptively self-assembles inside the body, minimizing the systemic side effects often caused by pharmaceutical chemicals.

What are the two principle functions of B cell and T cells?

B cells function primarily to produce highly specific antibodies that neutralize pathogens and mark them for destruction. T cells function to either directly kill infected or cancerous cells (cytotoxic T cells) or coordinate the overall immune response by activating other cells (helper T cells).

Where are B cells and T cells “educated” so they do not kill self-cells and how are

they “educated”?

B cells are educated in the bone marrow, while T cells are educated in the thymus. They undergo a rigorous selection process where cells with receptors that bind too strongly to the body's own "self" proteins are forced to undergo apoptosis (programmed cell death) or are rendered inactive.

What two key cells perform processing and presentation of antigens?

Dendritic cells and macrophages are the two primary cells that specialized in engulfing foreign pathogens, breaking them down, and presenting the pieces to naive T cells to launch an immune response.

What molecules are used to present peptides on the surface of antigen presenting

cells?

Antigen-presenting cells use Major Histocompatibility Complex (MHC) molecules—specifically MHC Class I and MHC Class II—to display peptide fragments on their surface for T cells to scan.

What do B cells and T cells differentiate into?

Activated B cells differentiate into antibody-secreting plasma cells and long-lived memory B cells. Activated T cells differentiate into effector T cells (such as cytotoxic or helper T cells) to fight the immediate infection, as well as memory T cells for future protection.

What is the difference between the B cell versus T cell receptors and what they

recognize?

B cell receptors (BCRs) can bind directly to free, intact, three-dimensional antigens floating in bodily fluids. In contrast, T cell receptors (TCRs) cannot bind to free antigens; they can only recognize broken-down antigen fragments that are bound and presented by an MHC molecule on another cell.

What is the clonal selection theory and what selects the clone?

The clonal selection theory states that the body generates millions of unique lymphocytes before birth, each recognizing a different random shape. The specific invading antigen itself selects the matching clone by binding to its receptor, triggering that specific cell to multiply.

How do autoimmune diseases arise and what is a major risk factor?

Autoimmune diseases arise when the immune system's tolerance mechanisms fail, causing B and T cells to mistakenly identify the body's own tissues as foreign invaders and attack them. A major risk factor for these diseases is a combination of genetic predisposition (such as specific HLA gene variants) and environmental triggers like viral infections.

What are the three antigen presenting cells?

The three professional antigen-presenting cells are dendritic cells, macrophages, and B cells.

What are the two mechanisms whereby cytotoxic T cells kill their target?

Cytotoxic T cells kill target cells either by releasing perforin and granzymes to punch holes in the membrane and trigger apoptosis, or by binding via the Fas/FasL pathway to signal the target cell to self-destruct.

What is the role of the T helper cell in B cell activation?

Helper T cells activate B cells by binding to the antigen presented by the B cell and releasing chemical signals called cytokines. This critical interaction provides the necessary "second signal" that tells the B cell to multiply and transform into antibody-producing factories.

What cytokine do regulatory B and T cells secrete?

Regulatory B and T cells primarily secrete the anti-inflammatory cytokine interleukin-10 (IL-10) and Transforming Growth Factor-beta (TGF-$\beta$) to suppress excess inflammation and maintain immune balance.

What does the T cell receptor bind to on viral or cancer cells?

On a viral or cancer cell, a cytotoxic T cell receptor binds directly to a foreign or mutated peptide fragment nested inside an MHC Class I molecule.

How do natural killer cells function?

Natural Killer cells destroy abnormal cells by scanning for the absence or downregulation of MHC Class I molecules, which viruses and tumors often hide to escape regular T cells. Once an abnormal cell is spotted, NK cells release cytotoxic granules to destroy it immediately without needing prior activation.

What types of covid-19 vaccines exist and which ones confer best protection?

COVID-19 vaccines include mRNA, viral vector, protein subunit, and inactivated virus platforms. Clinical data consistently shows that mRNA vaccines (like those from Pfizer-BioNTech and Moderna) generally confer the highest and most robust protection against severe disease and hospitalization.

What are advantages to the mRNA vaccines?

mRNA vaccines can be designed and manufactured incredibly fast because they only require a genetic sequence rather than growing live viruses. Furthermore, they trigger both a strong antibody response and a robust T-cell response without introducing any live or weakened virus into the patient.

What were complications from measles and polio vaccines?

Early formulations of the polio vaccine (specifically the 1955 Cutter incident) accidentally contained live virus that caused paralysis, while the older oral polio vaccine could occasionally mutate back into a virulent form. The measles vaccine can rarely cause a transient drop in blood platelets (thrombocytopenia) or mild, self-limiting febrile seizures in a tiny fraction of children.

What is herd immunity and why is it important to achieve during a pandemic?

Herd immunity occurs when a large enough portion of a population becomes immune to a disease, making person-to-person spread unlikely. Achieving this during a pandemic is vital because it breaks the chain of transmission and indirectly shields vulnerable individuals who cannot be safely vaccinated, such as newborns or the severely immunocompromised.

What disease did the boy in the bubble have?

David Vetter suffered from Severe Combined Immunodeficiency (SCID), a rare genetic disorder that left him born without a functioning immune system.

Did the bubble boy ever leave his bubble and play outside? How?

David lived almost his entire life inside sterile plastic environments to protect him from deadly germs. However, he did briefly step outside a few times using a specialized, flexible NASA-designed spacesuit that was connected to his sterile bubble via a protective tube.

How did they treat the bubble boy to cure his disease?

Doctors attempted to cure David by performing a bone marrow transplant using tissue from his sister, hoping it would seed his body with healthy, blood-cell-producing stem cells.

Was he cured of his disease? What did he die of?

Tragically, the treatment did not cure him. David died at age 12 from Burkitt's lymphoma, a cancer triggered by an undetected, dormant Epstein-Barr virus that had been hiding inside his sister's donated bone marrow.

What are the four hypersensitivity states, systems ande mechanisms involved and

examples of each?

The four types of hypersensitivity are Type I (Immediate, IgE-mediated mast cell degranulation; e.g., anaphylaxis), Type II (Cytotoxic, IgG/IgM binding to cell surface antigens; e.g., mismatched blood transfusion), Type III (Immune Complex, IgG/IgM forming circulating complexes that deposit in tissues; e.g., systemic lupus erythematosus), and Type IV (Delayed, T-cell mediated tissue damage; e.g., poison ivy contact dermatitis).

What is the difference between allergy, atopy, allergen and anaphylaxis?

An allergen is the harmless environmental substance that triggers a reaction, while atopy is the genetic predisposition to produce IgE antibodies against these allergens. An allergy is the actual clinical immune reaction resulting from that exposure, and anaphylaxis is the most severe, life-threatening systemic form of this reaction.

Are specific allergies inherited or is a predisposition to producing IgE inherited?

Specific allergies to unique substances are not directly inherited; rather, what is inherited is a general genetic predisposition to produce high levels of IgE antibodies (atopy). Environmental exposures determine which specific substances a person will ultimately become allergic to.

What is the hygiene hypothesis and why is it important?

The hygiene hypothesis suggests that a lack of early childhood exposure to infectious agents, microorganisms, and parasites suppresses the natural development of the immune system. It is important because it explains the dramatic rise in allergies and autoimmune diseases in modern, overly sanitized societies where the immune system defaults to an overreactive, allergic Th2 pathway.

Why is a Cesarean section a risk factor for food allergies?

A Cesarean section prevents a newborn from passing through the birth canal, meaning they miss out on critical exposure to the mother’s vaginal and fecal microbiota. This alters normal gut colonization, delaying immune system maturation and increasing the risk of food allergies.

What are the steps involved between sensitization to eliciting IgE from a mast cell?

During sensitization, an antigen is processed by an APC and presented to T cells, which prompt B cells to produce allergen-specific IgE antibodies that bind to the surface of mast cells. Upon a second exposure (elicitation), the allergen binds directly to and cross-links these surface-bound IgE molecules, triggering the mast cell to rapidly dump its inflammatory chemicals.

What are two key mediators of allergic symptoms and what do they do physiologically?

Histamine causes smooth muscle contraction in the lungs and rapid dilation and leakage of blood vessels, leading to swelling and redness. Leukotrienes act as potent bronchoconstrictors and mucus-stimulators, causing prolonged tightening of the airways during asthmatic responses.

What is the difference between hay fever and asthma?

Hay fever (allergic rhinitis) is an upper respiratory allergic reaction limited to inflammation of the nasal passages and eyes. Asthma is a lower respiratory disease where inflammation causes chronic swelling, mucus production, and bronchospasm (narrowing) of the lungs' airways.

What is eczema and what is a risk factor for children developing it?

Eczema (atopic dermatitis) is a chronic, inflammatory skin condition characterized by intensely itchy, dry red patches and a compromised skin barrier. A major risk factor for children developing it is a family history of atopic diseases (the "atopic triad" of eczema, asthma, and hay fever) or mutations in the filaggrin gene which weakens the skin barrier.

What is the range of symptoms that can occur with food allergy

Symptoms range from mild localized reactions like hives, lip swelling, and abdominal cramps to severe systemic effects like vomiting, throat swelling, wheezing, drop in blood pressure, and full-scale anaphylactic shock.

What causes drug allergies, what symptoms can occur and how is it treated?

Drug allergies occur when a medication acts as an antigen or binds to body proteins to trigger an unintended adaptive immune response. Symptoms range from mild skin rashes and hives to severe organ inflammation or life-threatening anaphylaxis; treatment requires immediately stopping the drug, administering antihistamines or epinephrine, and using systemic steroids for severe cases.

What is the difference between the RAST test and the Leucocyte histamine release test?

The RAST (Radioallergosorbent Test) is a blood test that measures the total concentration of static, allergen-specific IgE antibodies in a patient's serum. The Leucocyte Histamine Release Test is a functional assay that exposes the patient's live white blood cells to an allergen in a lab to physically measure how much histamine those cells actively secrete.

Why is skin testing performed and what is detected

Skin testing is performed by scratching or injecting tiny amounts of allergens into the skin to quickly assess a patient's sensitivity profile. The test detects the rapid swelling and redness ("wheal and flare" reaction) caused by localized mast cell degranulation, indicating the presence of allergen-specific IgE.

How do desensitization “shots” work?

Allergy shots work by injecting gradually increasing doses of an allergen over several years to retrain the immune system. This process shifts the body's response away from allergic IgE production and toward the production of "blocking" IgG4 antibodies, while also boosting regulatory T cells that suppress the allergic reaction.

What is Benadryl and how does it work

Benadryl (diphenhydramine) is a first-generation antihistamine that acts as an inverse agonist at H1 histamine receptors. By locking onto these receptors, it prevents free histamine from binding to tissue cells, effectively blocking allergic symptoms like itching, swelling, and runny nose.

What is an EpiPen and what is it used for?

An EpiPen is an auto-injector loaded with epinephrine (adrenaline) used for the emergency treatment of severe anaphylactic shock. It works rapidly to constrict blood vessels to raise dangerously low blood pressure, while simultaneously relaxing the smooth muscles of the lungs to reopen closed airways.

What are four ways to block the events in allergy?

Allergic events can be blocked by avoiding the allergen entirely, taking antihistamines to block H1 receptors, using mast cell stabilizers (like cromolyn sodium) to prevent the release of chemical mediators, or administering monoclonal antibodies (like Omalizumab) to bind up free IgE before it can attach to mast cells.

What is the classic example of type II hypersensitivity reaction that can kill a newborn

baby or a person receiving a transfusion

The classic example is Hemolytic Disease of the Newborn (Rh incompatibility), where a mother's IgG antibodies cross the placenta and destroy her fetus's red blood cells, or an Acute Hemolytic Transfusion Reaction from receiving mismatched ABO blood.

What are the steps involved in immune complex disease and what is the role of the

neutrophil?

First, antibodies bind to soluble antigens to create large immune complexes that deposit into blood vessel walls or tissues. Neutrophils are then chemically drawn to these deposits where they bind via their Fc receptors, release destructive lysosomal enzymes and reactive oxygen species, and cause local tissue damage and inflammation.

What is the difference between serum sickness and the arthus reaction?

Serum sickness is a systemic Type III reaction that occurs days to weeks after receiving foreign proteins, causing widespread immune complexes to deposit throughout the body (joints, kidneys, skin). The Arthus reaction is a localized, acute Type III reaction confined to a specific tissue area (like a vaccine injection site) in an individual who already has high levels of circulating antibodies against that specific antigen.

Why is type four hypersensitivity referred to as delayed hypersensitivity?

Type IV hypersensitivity is called "delayed" because it takes 48 to 72 hours for symptoms to peak. Unlike antibody-mediated reactions that happen within minutes, it requires time for antigen-presenting cells to migrate to lymph nodes, activate naive T cells, and allow those T cells to proliferate and travel back to the site of exposure to cause inflammation.

What is the mechanism behind the tuberculin test for TB?

The Mantoux skin test involves injecting a tiny amount of purified protein derivative (PPD) from the TB bacterium just under the skin. If a person has been exposed to TB before, memory T cells will migrate to the injection site over 48–72 hours, release inflammatory cytokines, and form a firm, raised bump (induration).

What is contact dermatitis, what is a hapten, what two major cell types are involved?

Contact dermatitis is a Type IV localized skin inflammation caused by direct physical contact with an environmental irritant or allergen. It involves haptens (tiny molecules that are too small to be antigenic on their own but trigger an immune response when bound to skin proteins), and is driven primarily by dendritic cells (APCs) and T lymphocytes (effector cells).

What mechanisms are involved in generating lupus, multiple sclerosis and type I

diabetes?

Lupus is driven by a systemic failure of B and T cell tolerance, leading to autoantibodies targeting the body's own nuclear DNA, forming destructive tissue complexes. Multiple Sclerosis occurs when autoreactive T cells cross the blood-brain barrier and target the protective myelin sheath of central nervous system neurons, while Type 1 Diabetes is caused by the targeted destruction of insulin-producing pancreatic beta cells by cytotoxic T cells.

What is the difference between types I and II diabetes and their causation?

Type 1 diabetes is an autoimmune disease caused by the destruction of pancreatic beta cells, resulting in an absolute lack of insulin production. Type 2 diabetes is a metabolic disorder primarily driven by lifestyle and genetics where cells become resistant to insulin, though the pancreas can still produce it.

What is molecular mimicry and why is it used to explain the origins of autoimmunity?

Molecular mimicry occurs when a foreign pathogen shares an almost identical amino acid sequence or structural shape with a normal human tissue protein. It explains autoimmunity because an immune response successfully mounted against the invading germ can accidentally cross-react and launch a permanent attack on the body's matching healthy organs.

What role does the gut microbiome play in autoimmune disease?

The gut microbiome regulates immune system development by maintaining the structural integrity of the intestinal wall and promoting the production of regulatory T cells (Tregs) via short-chain fatty acids. When the gut bacteria balance is disrupted (dysbiosis) or the gut barrier becomes leaky, foreign microbial antigens can leak into circulation, driving widespread chronic inflammation and triggering autoimmune reactions.

What organism is now believed to cause crippling autoimmune rheumatoid arthritis and

what evidence is provided?

Recent breakthrough research points to a newly isolated gut bacterium called Subdoligranulum didolesgii (and previously Prevotella copri) as a primary trigger for rheumatoid arthritis. The evidence shows that antibodies isolated from patients at risk for the disease directly bind to this organism, and when given orally to healthy mice, the bacterium causes them to develop autoimmune joint swelling and inflammation matching human arthritis.

What mechanism is involved in multiple sclerosis, what is the north south gradient

observation regarding incidence and how is it explained?

Multiple sclerosis involves the autoimmune destruction of myelin in the central nervous system, and epidemiological data shows a distinct "North-South gradient" where the incidence of MS increases significantly the further you live from the equator. This is explained by sunlight exposure; populations at higher latitudes get less UV radiation and produce less Vitamin D, a critical hormone that normally suppresses inflammatory T cells and promotes regulatory T cell function.

Why is Dr. Hartmann constantly bringing up the topic of vitamin D? Is he

obsessive/compulsive, biased, detached from reality or a member or some cult?

Dr. Hartmann is highlighting a massive body of legitimate, peer-reviewed clinical immunology literature showing that Vitamin D functions as a powerful immunomodulator, not just a bone nutrient. Far from being an eccentric obsession, emphasizing Vitamin D is a highly rational, evidence-based approach to correcting a widespread modern deficiency that directly compromises immune tolerance and elevates autoimmune disease risk.

What are the three major categories of microbial identification techniques?

The three major categories of microbial identification techniques are phenotypic (observing structural and biochemical traits), immunologic (using antibodies to detect antigens, or vice versa), and genotypic (analyzing the microbe's DNA or RNA).

What is the difference between phenotypic, immunologic and genotypic methods for identification of microscopic beasties?

• Phenotypic methods identify microbes by their physical appearance, growth characteristics, and enzymatic behavior (e.g., Gram staining or sugar fermentation).

• Immunologic methods rely on the highly specific binding between a pathogen's antigens and laboratory antibodies to confirm identity.

• Genotypic methods bypass culturing entirely by directly analyzing the microbe's specific genetic sequences, offering high speed and precision.

What is phage typing and what bacterial species is it used for?

Phage typing is a method that identifies specific bacterial strains by testing their susceptibility to infection by a known collection of bacteriophages (viruses that infect bacteria). It is most famously used for tracking and identifying epidemic strains of Staphylococcus aureus and Salmonella species.

What is the basic principle of serological testing?

The basic principle of serological testing is that an antibody will bind with extreme specificity to its matching antigen. By using a known laboratory antibody, clinicians can detect an unknown antigen in a patient's sample (or use a known antigen to detect specific antibodies in the patient's serum).

What cell is used in an agglutination test for the titer of influenza virus?

A red blood cell (erythrocyte) is used in influenza agglutination and hemagglutination inhibition tests. The influenza virus naturally binds to receptors on red blood cells, causing them to clump together into a visible lattice network.

How does the lateral flow test work- what reagents are moving?

In a lateral flow test, a liquid sample moves across a nitrocellulose strip via capillary action, carrying gold- or latex-labeled mobile antibodies along with it. If the target antigen is present, it binds to these moving antibodies and gets trapped by a line of stationary capture antibodies fixed further down the strip, producing a visible colored line.

How is a titer of a serum usually expressed?

A serum titer is usually expressed as the reciprocal of the highest dilution of the serum that still produces a visible, detectable reaction (e.g., if a 1:640 dilution is the last one to show clumping, the titer is reported as 640).

What is the principle behind a western blot and what steps are involved?

The Western blot identifies a specific protein within a complex mixture based on its molecular weight and antibody binding. The steps involve separating the proteins by size using gel electrophoresis, transferring (blotting) those separated proteins onto a sturdy membrane, and incubating the membrane with specific labeled antibodies to visualize the target protein band.

Why is a conjugated secondary antibody used in many serological tests?

A conjugated secondary antibody is used because it binds to the universal constant region of the primary antibody, allowing one standard laboratory bottle of secondary antibodies to work across many different tests. Furthermore, it amplifies the signal because multiple secondary antibodies can bind to a single primary antibody, making the test much more sensitive.

What is the difference between direct and indirect immunofluorescence testing?

Direct immunofluorescence applies a single, fluorescently labeled antibody directly to an unknown specimen to look for a matching target antigen. Indirect immunofluorescence applies an unlabeled primary antibody to the sample first, followed by a separate, fluorescently labeled secondary antibody that binds to the primary one, multiplying the glowing signal.

Why is a secondary antibody conjugated to an enzyme in ELISA testing?

The secondary antibody is conjugated to an enzyme so that when a colorless substrate is added later, the enzyme converts it into a highly visible, colored product. The intensity of this color change corresponds directly to how much target antigen or antibody was present in the original sample.

What is difference between the direct and indirect ELISA?

• Direct ELISA coats the testing well with the patient's sample to look directly for a specific antigen using a single, enzyme-linked primary antibody.

• Indirect ELISA coats the well with a known antigen to look for specific antibodies in the patient's serum, utilizing a secondary enzyme-linked antibody for final detection.

What is the difference between sensitivity and specificity?

• Sensitivity is the ability of a test to correctly identify those with the disease (minimizing false negatives).

• Specificity is the ability of a test to correctly identify those without the disease (minimizing false positives).

What is the polymerase chain reaction, how is it performed and what is the result?

PCR is a molecular technique used to rapidly mass-produce millions of copies of a specific DNA segment. It is performed by cycling a sample through three temperature phases—denaturation (separating strands), annealing (binding primers), and extension (copying with DNA polymerase)—resulting in a massive amplification of the target gene that can be easily detected.

What is the principle behind the Peptide-Nucleic acid Fish test and what is the function of both the peptide and the nucleic acid?

Peptide Nucleic Acid Fluorescent In Situ Hybridization (PNA-FISH) uses glowing probes to identify specific microbial genetic sequences directly inside a intact cell. The peptide backbone replaces the standard sugar-phosphate spine to give the probe neutral charge and extreme chemical stability, while the nucleic acid bases provide the precise genetic sequence matching required to bind to the target microbial RNA.

What is the principle behind the gene chip or microarray and what is detected by the chip?

A gene chip contains a grid pattern of thousands of unique, single-stranded DNA probes anchored to a glass slide. When fluorescently labeled cDNA from a sample is washed over the chip, it hybridizes to its matching probe, allowing a scanner to detect exactly which microbial genes are actively being expressed based on which spots glow.

During the separation of large segments of DNA why is a pulse field electrophoresis unit used?

Pulse-field electrophoresis is used because standard gel electrophoresis cannot separate exceptionally massive fragments of DNA, which simply stall out together in the gel matrix. By continuously alternating the direction of the electrical field ("pulsing" it), giant DNA segments are forced to twist and reorient themselves, allowing them to successfully separate by size.

What is the principle behind the use of mass spectrophotometry for identifying microorganisms in patient’s blood?

Mass spectrometry identifies bloodborne microbes by blasting a cultured colony fragment with a laser to ionize its structural proteins, then measuring how long it takes those proteins to travel through a vacuum tube (Time-of-Flight). Because every species possesses a totally unique protein mass profile, a computer can match this "molecular fingerprint" against a database to identify the organism in minutes.

What are the components of the upper and lower respiratory tract?

The upper respiratory tract includes the mouth, nose, nasal cavity, sinuses, pharynx, epiglottis, and larynx, while the lower respiratory tract consists of the trachea, bronchi, bronchioles, and alveoli.

What immune cell predominates in the alveoli, what class of antibody?

Alveolar macrophages are the predominant immune cells in the alveoli, working alongside Secretory IgA antibodies to neutralize pathogens.

What bacterium is a normal inhabitant of the lung yet causes pneumonia in elderly?

Streptococcus pneumoniae is a normal inhabitant of the upper respiratory tract that frequently causes severe bacterial pneumonia in elderly populations when structural immune defenses decline.

Why do we not have a vaccine for rhinitis?

We do not have a vaccine for rhinitis (the common cold) because it is caused by hundreds of distinct serotypes across multiple viral families—primarily Rhinoviruses—making a single universal vaccine virtually impossible.

What causes the symptoms of rhinitis?

Cold symptoms are not caused by direct viral destruction of tissues, but rather by the body's own localized inflammatory response, which releases histamine and bradykinin to trigger vascular leakage, mucus secretion, and tissue swelling.

What are two bacterial causes of acute otitis media?

Two major bacterial causes of acute otitis media are Streptococcus pneumoniae and Haemophilus influenzae.

What are four possible consequences of untreated Strep pyogenes infection?

Untreated Streptococcus pyogenes (Group A Strep) infections can lead to severe consequences including scarlet fever, rheumatic fever (causing heart damage), acute glomerulonephritis (kidney damage), and localized peritonsillar abscesses.

What are the mechanisms behind scarlet fever, rheumatic heart disease, and obsessive compulsive disorder (in children)?

Scarlet fever is caused by a bacterial erythrogenic toxin that damages capillaries to produce a red rash; rheumatic heart disease arises via molecular mimicry when anti-Strep antibodies mistakenly attack cardiac myosin; and childhood obsessive-compulsive disorder (PANDAS) occurs when those same cross-reactive antibodies target the basal ganglia in the brain.

What is used in the vaccine to prevent diptheria and what is the organism that causes it?

The diphtheria vaccine uses a purified, inactivated diphtheria toxoid to stimulate neutralizing antibodies against the disease-causing toxin produced by the bacterium Corynebacterium diphtheriae.

What are the functions of hemagglutinin and neuraminidase?

Hemagglutinin (H) binds to sialic acid receptors on host cells to allow the influenza virus to enter, while Neuraminidase (N) cuts those same receptors to allow newly replicated viral particles to break free and spread.

What is the difference between antigenic shift and antigenic drift and what are the mechanisms behind these phenomena?

Antigenic drift involves minor, gradual mutations within the viral genome during routine replication, whereas antigenic shift is a major, sudden change that occurs when two different influenza strains infect the same cell and swap entire gene segments via genetic reassortment.

What is FluMist and why is it not given to the elderly?

FluMist is a live-attenuated, temperature-sensitive influenza vaccine delivered as a nasal spray that is not given to the elderly because their naturally aging immune systems may not mount an effective response, or they may be at a higher risk for adverse effects from a live virus.

What are two reasons that tuberculosis is re-emerging as a disease?

Tuberculosis is re-emerging globally due to the widespread rise of multi-drug resistant bacterial strains (MDR-TB) and the high susceptibility of immunocompromised individuals, particularly those living with HIV.

What is a granuloma seen within tuberculosis and why does it occur?

A granuloma (or tubercle) is a tightly packed wall of macrophages, T cells, and fibroblasts that forms around Mycobacterium tuberculosis to physically isolate the bacteria and prevent them from spreading when the immune system cannot completely destroy them.

What is the genus and species nomenclature for tuberculosis?

The precise genus and species nomenclature for the primary causative organism of tuberculosis is Mycobacterium tuberculosis.

Why is tuberculosis considered a disease of poverty?

Tuberculosis is considered a disease of poverty because overcrowded housing, poor ventilation, malnutrition, and limited access to healthcare create the ideal environmental conditions for this airborne pathogen to spread and thrive.

What are five different means for diagnosing tuberculosis infection?

Tuberculosis can be diagnosed using a Mantoux tuberculin skin test (TST), an Interferon-Gamma Release Assay (IGRA) blood test, a chest X-ray, microscopic acid-fast staining of sputum, and rapid GeneXRT PCR DNA testing.

What mechanisms are involved in generating a positive tuberculin test?

A positive tuberculin skin test is a Type IV delayed-sensitised hypersensitivity reaction where memory T cells migrate to the PPD injection site, release inflammatory cytokines, and cause local tissue hardening (induration) over 48 to 72 hours.

What are two major consequences resulting from patient noncompliance in treating tuberculosis?

Patient noncompliance with the lengthy tuberculosis treatment regimen directly causes the selection and proliferation of highly dangerous multi-drug resistant bacterial strains (MDR/XDR-TB) and leads to clinical relapse or death for the individual.

How can a microscope quickly diagnose pneumonia caused by streptococcus pneumoniae?

A microscope can quickly diagnose pneumococcal pneumonia by showing distinct pairs of Gram-positive, lancet-shaped cocci (Streptococcus pneumoniae) surrounded by a clear, unstained halo indicative of a protective capsule.

What are four conditions that increase the probability of contracting pneumonia?

Four conditions that significantly increase the probability of contracting pneumonia are advanced age (over 65), chronic smoking (which paralyzes respiratory cilia), viral respiratory infections like the flu, and being on a mechanical ventilator in a hospital.

What is the major reason that children and old adults should receive the pneumococcal vaccine?

Young children and older adults should receive the pneumococcal vaccine because their immune systems are statistically the least equipped to produce antibodies against the bacterium's slippery polysaccharide capsule, leaving them highly vulnerable to invasive, fatal bloodstream infections.

What organism is an opportunistic pathogen found in aqueous environments that infects the lung?

Legionella pneumophila is an opportunistic pathogen found in natural and engineered aquatic environments (like cooling towers and plumbing systems) that causes severe Legionnaires' disease when contaminated water droplets are inhaled into the lungs.

What is a simple but effective means to prevent aspiration pneumonia in a hospital setting?

A simple but highly effective way to prevent aspiration pneumonia in hospitalized, bedridden patients is to elevate the head of the bed to a 30-to-45-degree angle to mechanically prevent stomach contents from traveling up the esophagus and spilling into the lungs.

What is the percentage of hospitalized patients that develop pneumonia from aspiration and what is the mortality rate?

Roughly 5% to 15% of all cases of community- and hospital-acquired pneumonias are caused by aspiration, and these infections carry a high mortality rate ranging from 20% to over 30% depending on the patient's underlying frailty.

What disease does the hantavirus cause and why is it considered an emerging disease?

Hantavirus causes Hantavirus Pulmonary Syndrome (HPS), a severe and frequently fatal respiratory disease that is considered an emerging infection because climate-driven spikes in rodent carrier populations are forcing increased contact between humans and aerosolized rodent waste.