MIC 205: Microbiology - Viruses, Antimicrobial Agents, Epidemiology, and Nonspecific Host Defenses

Comprehensive vocabulary flashcards covering virology, mechanisms of antimicrobial action, disease etiology and epidemiology, and innate nonspecific host defenses.

Virion

The extracellular physical state of a virus that possesses a protective protein coat (capsid) surrounding the nucleic acid genome, and occasionally an outer lipid envelope and specialized enzymes.

Capsid

A proteinaceous outer shell that encases and protects the viral nucleic acid genome and frequently provides attachment molecules to facilitate binding to susceptible host cells.

Capsomere

A protein subunit that self-assembles to construct the viral capsid, which may be composed of single or multiple distinct protein types.

Bacteriophage Structure

The structural morphology typical of complex bacterial viruses, featuring an icosahedral nucleic acid-containing head connected to a tail sheath, base plate, and tail fibers designed to penetrate bacterial cell walls.

Viral Envelope

A host-derived membrane structure composed of a phospholipid bilayer and embedded viral glycoprotein spikes that surrounds the capsids of certain animal viruses during viral release.

Obligate Intracellular Parasite

An organism or infectious agent (such as a virus) that lacks independent metabolic machinery, cytosol, and organelles, and is entirely dependent on host cell pathways for replication.

Burst Time

The precise period of time required to complete the entire viral lytic cycle, measured from the moment of initial attachment to the ultimate lysis and release of progeny virions.

Burst Size

The total quantitative yield of newly synthesized virions released from a given population of lysed host bacterial cells upon completion of the lytic cycle.

Lysogenic Replication

A temperate bacteriophage replication mechanism characterized by an extended period of dormancy during which viral DNA integrates into the bacterial host chromosome as a prophage.

Latency

A dormant state elicited by certain animal viruses where viral particles remain inactive within host cells for prolonged periods without producing symptoms, sometimes integrating permanently as proviruses.

Reverse Transcriptase

A unique, error-prone retroviral RNA-dependent DNA polymerase that synthesizes double-stranded complementary DNA using a single-stranded viral RNA template.

Hemagglutinin (H)

A major envelope glycoprotein of the influenza virus responsible for host cell recognition and binding to sialic acid surface receptors to trigger viral entry via endocytosis.

Neuraminidase (N)

An influenza viral envelope enzyme that enzymatically hydrolyzes sialic acid from host cell membranes and hemagglutinin, permitting release and dissemination of newly formed virions.

Antigenic Drift

Minor, gradual modifications in viral surface antigens (such as influenza hemagglutinin and neuraminidase) resulting from accumulated point mutations over time.

Antigenic Shift

A major, abrupt alteration in viral surface antigens caused by genomic reassortment when two distinct viral strains coinfect the same host cell, often leading to pandemics.

Neoplasia

A pathological state of uncontrolled, unregulated cell division in a multicellular animal that leads to the accumulation of abnormal cellular tissue masses termed tumors.

Viroid

A plant pathogen composed strictly of a tiny, circular piece of infectious single-stranded RNA that lacks a protein capsid and does not encode functional proteins.

Prion

A proteinaceous infectious agent devoid of nucleic acids that causes fatal spongiform encephalopathies when the abnormal $\beta$-pleated sheet conformer (prion PrP) refolds normal $\alpha$-helical cellular PrP.

Selective Toxicity

The fundamental antimicrobial property where an administered therapeutic agent selectively targets and destroys microbial pathogens while causing negligible harm to host tissues.

Salvarsan

An arsenic-based chemical compound discovered by Paul Ehrlich in 1910 to treat syphilis; considered the first modern chemotherapeutic agent.

Beta-lactam

A prominent class of antibacterial drugs containing a functional four-membered $\beta$-lactam ring that competitively inhibits transpeptidase enzymes responsible for cross-linking NAM subunits during peptidoglycan synthesis.

Beta-lactamase

A bacterial resistance enzyme (also called penicillinase) that breaks the internal bond of the $\beta$-lactam ring, converting antibiotics like penicillin into inactive derivatives.

Aminoglycosides

A class of broad-spectrum antibiotics (such as streptomycin) that bind specifically to the bacterial $30\text{S}$ ribosomal subunit, altering its tertiary conformation and causing mRNA to be misread.

Amphotericin B

A fungicidal polyene drug that selectively targets and binds ergosterol in fungal cytoplasmic membranes, assembling trans-bilayer pores that destroy membrane permeability and lead to cytoplasmic leakage.

Minimum Inhibitory Concentration (MIC)

The lowest quantitative concentration of an antimicrobial drug that visibly inhibits the growth of a target microorganism following in vitro incubation.

Minimum Bactericidal Concentration (MBC)

The lowest concentration of an antibacterial agent necessary to kill at least $99.9\%$ of the initial bacterial inoculum rather than merely suppress its replication.

Antimicrobial Synergism

The therapeutic strategy of administering two or more antimicrobial drugs concurrently to produce an effect greater than the sum of their individual activities and suppress resistant mutants.

Commensalism

A symbiotic relationship in which one participating organism derives biological benefits while the second organism remains uninjured and unbenefited.

Amensalism

A symbiotic ecological interaction in which one organism is harmed or inhibited while the other organism neither gains a metabolic benefit nor experiences harm.

Resident Microbiota

Microorganisms that normally colonize body surfaces throughout an individual's lifetime without inducing pathology under standard physiological conditions.

Transient Microbiota

Microorganisms that reside transiently on or within host tissues for hours to months before being eliminated by competition, host defenses, or physical-chemical changes.

Opportunistic Pathogen

A mutualistic or commensal microorganism of the normal flora that gains the capacity to cause clinical infection when host immunity drops, normal flora balance shifts, or it enters an abnormal anatomical niche.

Fomite

An inanimate object, surface, or substance (such as a needle, toothbrush, or doorknob) that inadvertently transfers pathogenic microorganisms from one host to another.

Biological Vector

An arthropod or biting animal that not only transfers pathogenic agents between hosts but also serves as an obligatory site for a developmental or replicative stage of the pathogen's life cycle.

Mechanical Vector

A vector organism (such as a housefly or cockroach) that passively conveys infectious agents on feet or exterior body surfaces without supporting internal pathogen reproduction.

Parenteral Route

A non-anatomical pathway of pathogen transmission wherein physical trauma (such as punctures, injections, bites, or deep cuts) deposits microbes directly into underlying tissues or the bloodstream.

Zoonosis

An infectious disease naturally transmitted from an animal vertebrate host to human populations, frequently terminating without subsequent secondary transmission between humans.

Koch's Postulates

A formal series of four experimental criteria formulated by Robert Koch to confirm the specific causal link connecting an isolated pathogenic microorganism to a definite disease.

Symptoms

Subjective signs of pathology that are felt and reported exclusively by the afflicted patient (such as pain, headache, or nausea) that cannot be directly measured by an observer.

Signs

Objective and clinically observable indications of disease (such as erythema, fever, swelling, or vital sign abnormalities) that can be measured or observed by healthcare clinicians.

Syndrome

A characteristic constellation of concurrent signs and symptoms that systematically defines a specific medical condition, clinical disorder, or disease entity.

Extracellular Enzymes (Coagulase and Kinase)

Virulence factors secreted by bacteria that manipulate host vascular structures, wherein coagulase clots plasma proteins to hide bacteria from defenses, and kinase later dissolves the clot to release them into tissues.

Siderophore

A high-affinity iron-chelating molecule synthesized and secreted by pathogenic bacteria (like E. coli) to scavenge essential ferric iron ($\text{Fe}^{3+}$) from host fluids and proteins.

Toxemia

A systemic clinical state resulting from the presence and circulation of microbial toxins within the host bloodstream, distributing pathology distantly from the initial point of colonization.

Healthcare-Associated Infection (HAI)

An infection acquired by a patient within a clinical hospital or healthcare setting while receiving diagnostic or therapeutic care; historically designated as a nosocomial infection.

Incidence

An epidemiological calculation expressing the total count of brand new clinical disease cases arising within a specified population group during a designated timeframe.

Prevalence

An epidemiological measure quantifying the total cumulative number of active disease cases present in an identified geographic population at a given slice of time.

Endemic Disease

An infectious pathology or transmissible agent that displays a relatively stable, predictable, and continuous background occurrence within an identifiable geographical territory.

Epidemic

A sudden statistical surge in the number of recorded disease cases substantially above normal expectations within a specific region or defined population cohort.

Pandemic

A widespread epidemiological outbreak wherein an epidemic expands across expansive geographic regions, typically spanning multiple continents or global territories.

Index Case

The earliest documented or presenting patient exhibiting an infectious condition in an epidemiological investigation whose tracing guides public health authorities to the outbreak source.

Epidermis

The superficial layer of the cutaneous membrane made of multiple compact strata of keratinized epithelial cells that constantly desquamate to remove adhered pathogenic microorganisms.

Dendritic Cells

Specialized phagocytes (such as Langerhans cells in the skin) distributed throughout epidermal and mucosal surfaces that ingest invaders and alert adaptive lymphocytes.

Lysozyme

A protective bactericidal enzyme naturally secreted in sweat, lacrimal fluid, and saliva that digests peptidoglycan cell walls by breaking covalent bonds between NAG and NAM.

Sebum

An oily lipid substance secreted by cutaneous sebaceous glands that coats keratin surfaces, preserves skin pliability against tearing, and generates an acidic inhibitory barrier.

Microbial Antagonism

The protective barrier activity exerted by normal resident microbiota against prospective pathogens via competition for vital resources, nutrient consumption, and toxic pH reduction.

Defensins

Small, positively charged antimicrobial peptides secreted onto mucosal and dermal surfaces that damage pathogen integrity by punching holes in cytoplasmic membranes.

Hematopoiesis

The process of blood cell differentiation and proliferation occurring within pluripotent red bone marrow stem cells, generating erythrocytes, platelets, and leukocytes.

Diapedesis

The active extravasation process whereby circulating inflammatory leukocytes squeeze between endothelial junctions of permeable capillaries to enter infected extravascular tissue beds.

Phagocytosis

A cellular immune defense mechanism wherein specialized phagocytes capture, engulf, and degrade foreign particles or microbes via a five-step progression: chemotaxis, adherence, ingestion, digestion, and elimination.

Opsonization

The biological process of marking or coating foreign pathogenic targets with immune proteins (such as antibodies or complement fragments) to facilitate adherence and engulfment by phagocytic cells.

Pyrogens

Exogenous or endogenous chemical factors (including bacterial toxins, antigen-antibody complexes, or Interleukin-1) that trigger the host hypothalamus to adjust the body's baseline temperature past $37\,^\circ\text{C}$.

Interferon System

A nonspecific antiviral cytokine defense where virus-infected cells secrete interferons to signal adjacent uninfected cells, stimulating them to transcribe and translate inactive antiviral proteins (AVPs) that halt viral spread upon activation.

Membrane Attack Complex (MAC)

A circular cytotoxic protein pore assembled in target pathogen membranes via activation of the terminal complement cascade, inducing rapid cytolytic destruction via osmotic influx.