Definitive Study Notes on Medical Virology, Bacteriology, Antimicrobials, and Oral Pathology

Vocabulary flashcards covering core concepts, viral structures, viral diseases, vaccines, hepatitis types, HIV/AIDS, antimicrobials, tuberculosis, and syphilis based on the lecture material.

Viruses

Acellular, ultramicroscopic ($10\text{–}100\,\text{nm}$) obligate intracellular parasites containing either DNA or RNA, which lack organelles and metabolic machinery and replicate solely inside host cells.

Virion

A complete, fully assembled, infectious extracellular virus particle composed of nucleic acid and an outer protein shell.

Capsid

The protective protein coat surrounding the nucleic acid core of a virus, composed of individual protein units called capsomeres.

Nucleocapsid

The complex unit formed by the viral nucleic acid genome combined with its surrounding protein capsid.

Capsomeres

The protein subunits that aggregate together to form the capsid of a virus particle.

Peplomers

Glycoprotein spike structures projecting from the lipoprotein envelope of enveloped viruses that function in attachment to host cell receptors.

Viroids

Infectious plant pathogens consisting of small ($<300\text{–}400$ nucleotides), naked, covalently closed circles of single-stranded RNA that replicate using host enzymes without a capsid or human disease associations.

Prions

Proteinaceous infectious particles lacking nucleic acids (DNA or RNA) that infect neural tissues and cause transmissible spongiform encephalopathies like Creutzfeldt-Jakob Disease (CJD).

Bacteriophages

Complex structural viruses (head and tail) that specifically infect bacterial cells by injecting their genetic material.

Lytic Cycle

A viral replication cycle in which a virulent phage infects a host, replicates rapidly, assembles new virions, and lyses the host cell, leading to host death.

Lysogenic Cycle

A viral life cycle in which temperate phage DNA integrates into the bacterial genome as a dormant prophage and replicates passively along with host cell division.

Prophage

Viral genetic material that has been integrated into the host bacterial chromosome during the lysogenic cycle.

Lysogenic Conversion

The alteration of bacterial cell phenotypic properties induced by an integrated prophage, which enables organisms such as Corynebacterium diphtheriae, Streptococcus pyogenes, and Clostridium botulinum to produce exotoxins.

Viral Tropism

The host tissue or cell specificity exhibited by a virus, determined by precise interactions between viral surface structures and host cell surface receptors.

Attenuated Vaccine

A vaccine formulation containing live microorganisms or viruses weakened under adverse conditions, losing virulence while retaining immunogenicity to induce strong, long-lasting immunity.

Killed Vaccine

A vaccine prepared by deactivating whole pathogens with heat or chemicals (such as Formalin), which cannot replicate but generate immune memory; safe for immunocompromised patients.

Genetically Engineered Vaccine

A recombinant or subunit vaccine produced via biotechnology containing only specific non-infectious antigens or proteins of a pathogen.

Hemagglutinin (H)

An influenza surface glycoprotein spike that binds to host cell receptors to facilitate viral entry and host attachment.

Neuraminidase (N)

An influenza surface enzyme spike that cleaves host cell receptors to allow newly assembled viral particles to escape from infected host cells.

Antigenic Drift

The gradual accumulation of small viral gene mutations over time causing minor alterations in surface proteins (H and N) and leading to seasonal epidemics.

Antigenic Shift

A sudden, major genetic change occurring when two different influenza strains co-infect a single host cell and undergo genome segment reassortment, giving rise to novel pandemic subtypes.

Herpetic Whitlow

A herpes simplex virus (HSV-1 or HSV-2) infection of the fingers, traditionally acquired by dental personnel through occupational exposure to virus-contaminated saliva or oral lesions.

Varicella-Zoster Virus (VZV)

Human Herpesvirus 3 (HHV-3), which causes varicella (chickenpox) as a primary infection and herpes zoster (shingles) upon reactivation from sensory ganglia.

Epstein-Barr Virus (EBV)

Human Herpesvirus 4 (HHV-4), a lymphotropic virus spread via saliva that infects B cells and causes infectious mononucleosis, Burkitt lymphoma, nasopharyngeal carcinoma, and oral hairy leukoplakia.

Cytomegalovirus (CMV)

Human Herpesvirus 5 (HHV-5), which causes mononucleosis-like illness, congenital birth defects (deafness, intellectual disability) in neonates, and retinitis in AIDS patients.

Human Papillomavirus (HPV)

An epitheliotropic DNA virus causing warts and epithelial tumors, with high-risk types 16 and 18 responsible for cervical and oropharyngeal cancers.

Hepatitis A Virus (HAV)

A non-enveloped single-stranded RNA picornavirus transmitted by the fecal-oral route, causing acute, self-limiting liver infection without a chronic carrier state.

Hepatitis B Virus (HBV)

An enveloped double-stranded DNA hepadnavirus transmitted via blood and body fluids, presenting an occupational hazard for dental personnel and leading to chronic infection, cirrhosis, and liver cancer.

Hepatitis C Virus (HCV)

An enveloped single-stranded RNA flavivirus transmitted through parenteral blood contact, with roughly 80% of infected individuals developing chronic hepatitis.

Hepatitis D Virus (HDV)

A defective single-stranded RNA deltavirus that requires active Hepatitis B virus (borrowing HBsAg) to survive and replicate, worsening HBV liver disease severity.

Human Immunodeficiency Virus (HIV)

An enveloped single-stranded RNA retrovirus containing reverse transcriptase that infects CD4+ T lymphocytes, progressively impairing adaptive immunity.

Acquired Immunodeficiency Syndrome (AIDS)

The advanced, late stage of HIV infection characterized by a CD4+ T-cell count below $200\,\text{cells/}\mu\text{L}$ or the onset of AIDS-defining opportunistic infections and malignancies.

Post-Exposure Prophylaxis (PEP)

A combination antiretroviral therapy (ART) protocol initiated ideally within 2 hours of occupational needle-stick exposure to minimize the risk of HIV seroconversion.

Antimicrobial

A broad umbrella term for any chemical substance that kills (microbicidal) or inhibits the growth (microbistatic) of microorganisms.

Antibiotic

A substance produced naturally by a microorganism (or synthesized chemically) that inhibits or kills other microorganisms.

Bacteriostatic

The property of an antimicrobial agent that inhibits bacterial growth and cell division without directly killing the organism.

Bactericidal

The property of an antimicrobial agent that directly kills bacteria.

Glucosyltransferase

An enzyme produced by Streptococcus mutans that breaks down sucrose and converts glucose into extracellular dextran, allowing bacteria to adhere to tooth enamel.

Sulfonamides

Synthetic bacteriostatic drugs that inhibit bacterial folic acid synthesis required for DNA/RNA production, exerting selective toxicity since human cells acquire folic acid from dietary sources.

Chlorhexidine (CHX)

A broad-spectrum antiseptic agent recognized as one of the most effective chemotherapeutic oral rinses for controlling dental biofilm.

Periostat

A systemic low-dose doxycycline hyclate ($20\,\text{mg}$) tablet that manages periodontal disease by suppressing host tissue-destroying collagenase enzymes rather than acting antibacterially.

Arestin

A locally delivered antibiotic system consisting of minocycline HCl ($1\,\text{mg}$) microspheres placed into infected periodontal pockets following scaling and root planing.

Mycobacterium tuberculosis

An acid-fast, obligate aerobic rod-shaped bacterium transmitted via airborne droplet nuclei from coughing or sneezing that causes pulmonary tuberculosis.

Tuberculin Skin Test (Mantoux)

A diagnostic intradermal test measuring delayed hypersensitivity response to tuberculin purified protein derivative, indicating exposure to M. tuberculosis or prior BCG vaccination rather than active disease.

Interferon-Gamma Release Assays (IGRAs)

Diagnostic blood tests for tuberculosis that measure immune reactivity to M. tuberculosis without generating false-positive results from prior BCG vaccination.

Treponema pallidum

A thin, motile, microaerophilic spirochete bacterium that acts as the causative agent of syphilis.

Chancre

A painless, indurated, highly contagious ulcer with a firm base that develops at the site of inoculation during primary syphilis.

Mucous Patches

Highly infectious, gray-white mucosal plaques on a red base that present on oral mucosa, soft palate, and tongue during secondary syphilis.

Gumma

A soft, tumor-like granulomatous lesion with central necrosis characteristic of tertiary syphilis, capable of causing palatal perforation.

Hutchinson's Incisors

A dental manifestation of congenital syphilis presenting as notched, screwdriver- or bell-shaped permanent central incisors.

Mulberry Molars

A congenital syphilis dental abnormality where permanent first molars exhibit malformed, berry-like crowns with poorly developed cusps.