Microbiology Exam 3 Review: Epidemiology, Antimicrobial Therapy, and Immunology

Comprehensive vocabulary flashcards covering epidemiology, microbial control, antimicrobial mechanisms, resistance, innate immunity, and adaptive immunity for Microbiology Exam 3.

Prevalence

The proportion of all existing cases in a population at a specified time divided by the total population size; it is influenced by incidence, disease duration, or both.

Incidence

The number of new cases of a disease that develop in a population during a defined period.

Sporadic Disease

A pattern of disease occurrence characterized by infrequent and irregular cases (e.g., an isolated tetanus case in a county).

Endemic Disease

A disease that is constantly present at an expected baseline level within a particular geographic area or population (e.g., a common cold persistently present in a region).

Epidemic

A sudden increase in the number of disease cases clearly above baseline expectation across a larger geographic region (e.g., an unexpected regional rise in measles).

Pandemic

An epidemic that has spread over multiple countries or continents (e.g., worldwide spread of a novel influenza strain).

Hospital-Acquired Infections (HAIs)

Infections acquired while receiving healthcare in a medical facility, such as catheter-associated UTIs, central-line bloodstream infections, surgical-site infections, and ventilator-associated pneumonia.

Communicable Disease

An infectious disease caused by a pathogen that is capable of being transmitted from one host to another (e.g., influenza).

Fomite

A contaminated inanimate object (such as a doorknob or shared medical equipment) that facilitates indirect transmission of an infectious agent.

Mechanical Vector

An animal or insect that transports a pathogen externally on its body without the pathogen multiplying or developing inside the vector (e.g., a housefly transferring pathogens to food).

Biological Vector

A vector in which a pathogen undergoes replication, biological development, or a specific life cycle stage before transmission to a new host (e.g., a mosquito transmitting malaria).

Sterilization

A physical or chemical process that completely destroys or eliminates all forms of microbial life, including bacterial endospores (e.g., steam autoclaving).

Antisepsis

The application of antimicrobial chemical agents to living tissue to reduce or inhibit microbial load, which does not reliably eliminate bacterial endospores or sterilize skin.

Prophylaxis

A medical intervention or preventive antimicrobial treatment administered prior to infection or disease onset to prevent disease development.

Kirby–Bauer Disk Diffusion Test

A standardized agar plate assay where antibiotic-impregnated disks are placed on a bacterial lawn, and diameters of the resulting zones of inhibition are measured in millimeters to categorize an isolate as susceptible, intermediate/susceptible-increased-exposure, or resistant.

Vancomycin

A cell-wall synthesis inhibitor targeted against Gram-positive bacteria, including MRSA; administered orally specifically to treat Clostridioides difficile in the gastrointestinal tract.

Azithromycin and Streptomycin

Antibacterial agents that bind bacterial ribosomal subunits to inhibit protein synthesis; used for respiratory infections, chlamydia, and atypical/zoonotic bacteria such as plague or tularemia.

Trimethoprim–Sulfamethoxazole (TMP–SMX)

A synergistic antibiotic combination that sequentially blocks bacterial enzymatic steps in folate synthesis; commonly used for UTIs, selected MRSA skin infections, and Pneumocystis pneumonia.

Ciprofloxacin / Levofloxacin

Fluoroquinolone antibiotics that inhibit bacterial DNA gyrase and topoisomerase IV, providing broad-spectrum coverage for pneumonia, complicated UTIs, and traveler's diarrhea.

Fluconazole

An antifungal agent that inhibits the fungal 14-$\alpha$-demethylase enzyme, impairing ergosterol biosynthesis in yeast such as Candida and Cryptococcus.

Artemisinin Derivatives

Antimalarial agents targeting Plasmodium species, activated by heme/iron to release toxic reactive radicals; used in combination therapies.

Ivermectin

An antiparasitic agent that activates glutamate-gated chloride channels in nematodes and ectoparasites, causing hyperpolarization and flaccid paralysis; treats strongyloidiasis, onchocerciasis, and scabies.

Zidovudine (AZT)

A nucleoside reverse-transcriptase inhibitor (NRTI) that causes premature DNA chain termination during HIV replication.

Remdesivir

An antiviral nucleotide analogue that inhibits the RNA-dependent RNA polymerase of SARS-CoV-2 to suppress viral replication in selected COVID-19 patients.

Five Mechanisms of Antibiotic Resistance

Bacterial strategies to resist antimicrobials: (1) enzymatic inactivation, (2) target alteration, (3) reduced permeability via porin loss, (4) active efflux pumps, and (5) metabolic pathway bypass or target overproduction.

Neutrophils

The most abundant polymorphonuclear leukocytes; serve as rapid first responders of the innate immune system to phagocytose and destroy invading bacteria and fungi.

Eosinophils

Innate granulocytes primarily involved in immune defense against parasitic helminths and in the modulation of allergic inflammation.

Basophils

Circulating innate granulocytes that release histamine, heparin, and other chemical mediators in response to IgE binding to promote allergic inflammation.

Macrophages

Tissue-resident mononuclear phagocytes derived from circulating monocytes that engulf microbes and debris, secrete signaling cytokines, and present antigens on MHC molecules.

Phagocytosis

A multistep innate defense mechanism consisting of: (1) chemotaxis, (2) adherence via PAMP/opsonin recognition, (3) ingestion forming a phagosome, (4) killing/digestion within a phagolysosome, and (5) exocytosis of debris.

Type I Interferons (IFN-α and IFN-β)

Host cytokines secreted by virus-infected cells and innate cells that trigger an antiviral state in neighboring uninfected cells and enhance immune surveillance.

Interferon-gamma (IFN-γ)

A host cytokine produced predominantly by NK cells and T lymphocytes that potently activates macrophages and enhances cell-mediated immunity.

Complement System

A cascade of liver-derived circulating serum proteins activated via classical, lectin, or alternative pathways to promote opsonization, leukocyte recruitment/inflammation, and pathogen lysis via the membrane attack complex.

B Lymphocytes

Adaptive immune cells that mature in bone marrow, recognize native antigen via membrane-bound immunoglobulins, and differentiate into plasma cells to secrete protective antibodies.

CD4+ Helper T Lymphocytes

T cells that recognize exogenous antigens presented on MHC class II molecules of antigen-presenting cells and secrete cytokines to coordinate macrophages, cytotoxic T cells, and B cell proliferation.

CD8+ Cytotoxic T Lymphocytes (CTLs)

T cells that recognize endogenous antigens presented on MHC class I molecules and directly kill virus-infected or abnormal cells using lytic enzymes (e.g., perforin and granzymes).

Agglutination

An antibody-mediated effector mechanism where multivalent antibodies cross-link cells or particulate antigens into visible clumps to facilitate their removal.

Opsonization

The coating of microbial pathogens by antibodies or complement fragments (such as C3b) to facilitate recognition and uptake by phagocytic cells.

Neutralization

An antibody function whereby antibodies bind directly to bacterial toxins or surface proteins of viruses, preventing binding and entry into host cells.

Immunoglobulin G (IgG)

The predominant immunoglobulin class in serum during secondary immune responses; mediates neutralization, opsonization, and complement activation, and crosses the placenta.

Immunoglobulin M (IgM)

The first immunoglobulin class produced in a primary humoral response; exists as a pentamer in secretions with high avidity for agglutination and classical complement fixation.

Immunoglobulin A (IgA)

A secretory dimer that protects mucosal surfaces by preventing pathogen adherence in saliva, tears, colostrum/breast milk, and respiratory and gastrointestinal tracts.

Immunoglobulin E (IgE)

An antibody class that binds tightly via its Fc region to receptors on mast cells and basophils, mediating allergic reactions and protection against parasitic worms.

Natural Active Immunity

Adaptive immune protection and long-lived immunological memory developed by an individual's own immune system in response to exposure to an infectious pathogen.

Artificial Active Immunity

Immune protection and immunological memory elicited in a host through the administration of a vaccine or toxoid.

Natural Passive Immunity

Immediate, temporary protection conferred to an infant via preformed maternal antibodies acquired transplacentally (IgG) or through colostrum and breast milk (IgA).

Artificial Passive Immunity

Short-term, immediate protection achieved by injecting a recipient with preformed pooled immune globulin or monoclonal antibodies produced outside the host.