Infection, Infectious Diseases, and Cancer Biology

Comprehensive vocabulary flashcards covering microbial infection, pathogenesis, modes of transmission, bacterial and viral biology, and the principles of neoplasia, carcinogenesis, and oncology management.

Resident Flora

The non-disease-producing microorganisms naturally inhabiting the human body as part of the normal human microbiome.

Opportunistic Microorganisms

Microorganisms within the normal microbiome that cause disease only when they overproliferate or are introduced into sterile tissues.

Primary Pathogens

Disease-causing microorganisms capable of binding to host cells, causing cellular damage, disrupting metabolism, or releasing toxins regardless of host immune status.

Reservoir

The natural organism or environmental setting where a pathogen continuously resides and survives.

Pathogenicity

The inherent capacity of a pathogen to cause suffering and disease.

Virulence

The degree of pathogenicity or strength of a microbe, reflecting how severe of a disease it can cause.

Infectivity

The ability of a pathogen to cause infection, measured by how readily it is transmitted from host to host.

Toxigenicity

The capacity of a pathogenic microorganism to produce harmful toxins.

Immunogenicity

The ability of a pathogen to trigger an immune response in the host.

Antigenic Variability

The ability of a pathogen to rapidly mutate its surface antigens, facilitating evasion of host immunity and necessitating newly designed vaccines.

Coinfection

The occurrence of two different infections simultaneously, transmitted by the same route at the exact same time.

Superinfection

A secondary infection that establishes itself when a host's immune defenses have been compromised by an initial infection.

Biofilm

A protective matrix composed of secreted proteins and glycoproteins that encloses bacteria or yeasts, shielding them from host immune defenses and antibiotics.

Microbial Latency

A pathogen survival mechanism wherein a bacterium or virus downregulates its metabolic activity to remain dormant within host tissues without triggering clearance.

Vertical Transmission

A direct mode of pathogen transmission occurring from mother to baby in utero or during birth.

Airborne Transmission

Transmission of pathogens carried in fine water vapor over distances of 25 to 30 feet, distinct from short-range droplet transmission occurring within 6 feet.

Vector Transmission

Transmission of an infectious agent from one host to another via an intermediate species, such as an arthropod or rabid animal.

Incubation Period

The initial post-exposure phase during which a patient remains asymptomatic while the pathogen increases in number.

Prodrome

The early stage of an infection marked by vague, non-specific clinical signs and symptoms that precede acute clinical illness.

Convalescence

The recovery period of an infection during which acute symptoms resolve and tissue healing occurs.

Septicemia

A life-threatening complication of infection where microorganisms proliferate in the bloodstream, triggering systemic vasodilation, hypotension, and potential septic shock.

Mycoses

Infections caused by eukaryotic fungal pathogens, which can exist as unicellular yeasts or multicellular filamentous molds.

Candida

An opportunistic fungal organism infecting skin and mucous membranes, clinically manifested by erythema, itching, burning, or cottage-cheese-like exudates.

Maceration

The softening and breakdown of skin or mucosal tissue caused by prolonged exposure to moisture, facilitating fungal colonization.

Protists

Unicellular eukaryotic microorganisms that can cause parasitic infections, including amoebae, Giardia, and Plasmodium.

Helminths

Multicellular parasitic worms that cause human infections, including tapeworms, hookworms, and pinworms.

Prions

Infectious, abnormally folded proteins that accumulate in nervous tissue and induce normal proteins to misfold, causing conditions such as Bovine Spongiform Encephalopathy and Creutzfeldt-Jakob disease.

Bacterial Shapes

The three primary morphological forms used to identify and name bacteria: spherical (cocci), rod-shaped (bacilli), and spiral forms.

Exotoxins

Toxic polypeptides synthesized and actively secreted by living bacterial cells into surrounding tissues.

Endotoxins

Lipopolysaccharide components of the outer membrane of Gram-negative bacteria released during cell lysis that cause severe inflammatory responses and septic shock.

Binary Fission

The asexual reproductive mechanism used by bacterial cells where elongated cells replicate their chromosome, form a cross-wall, and cleave into two distinct cells.

Bacterial Growth Curve

A standard population growth trajectory consisting of the lag phase, exponential (log) phase, stationary phase, and death phase.

Transduction

Horizontal transfer of bacterial DNA from one bacterium to another mediated by a bacteriophage vector.

Transformation

An energy-requiring form of horizontal gene transfer in which a competent bacterium binds and incorporates exogenous naked DNA into its genome.

Bacterial Conjugation

Direct horizontal transfer of genetic material between two bacteria in physical contact, mediated by a sex pilus and transfer of an F plasmid.

Bacteriophages

Viruses that selectively infect bacterial hosts, classified into virulent phages that execute the lytic cycle and temperate phages that utilize the lysogenic cycle.

Tissue Tropism

The specific affinity of a pathogen or metastasizing cell to infect or colonize a particular tissue type or organ.

Staphylococcus aureus

A Gram-positive coccus that secretes multiple destructive exotoxins and enzymes, causing manifestations such as scalded skin syndrome, toxic shock syndrome, and osteomyelitis.

Streptococcus pyogenes

A Group A beta-hemolytic Gram-positive coccus equipped with M protein to block complement deposition, a C5a peptidase, and hyaluronidase.

Clostridium difficile

A Gram-positive, spore-forming bacillus producing Toxin A and Toxin B that destroys colonic mucosal cells to produce pseudomembranes when resident flora is depleted.

Neoplasm

An abnormal tissue mass characterized by uncontrolled cell proliferation and impaired differentiation resulting from genetic mutations.

Carcinogenesis

The cellular and biological process underlying the initiation, origination, and progression of malignant neoplasms.

Benign Neoplasm

A non-cancerous, well-circumscribed, typically encapsulated, and differentiated mass that does not invade local tissues or metastasize.

Malignant Neoplasm

An aggressive, poorly circumscribed, poorly differentiated mass of cells capable of local tissue invasion and distant metastasis.

Sarcoma

A malignant tumor originating from mesenchymal or connective tissues such as bone, muscle, or cartilage.

Carcinoma

A malignant neoplasm derived from epithelial cells, including squamous and glandular lineages.

Carcinoma in Situ

A malignant epithelial neoplasm that has not breached the basement membrane and remains localized to its tissue of origin without invading connective tissue.

Mesothelioma

A malignant tumor affecting the pleural membranes, commonly developing 10 to 15 years after asbestos exposure.

Multiple Myeloma

A hematologic malignancy of plasma cells (activated B lymphocytes) resulting in abnormal accumulation of antibody fragments.

Tumor Initiation

The initial, irreversible stage of carcinogenesis caused by a primary genetic mutation in a somatic or germline cell.

Tumor Promotion

The intermediate stage of carcinogenesis where mutated cells are stimulated to proliferate by sustained promoting factors, such as chronic inflammation.

Tumor Progression

The final stage of carcinogenesis where a neoplastic mass acquires autonomy, growing and invading continuously without requiring external growth stimuli.

Clonal Expansion

The proliferative amplification of identical cells derived from a single mutated ancestral progenitor cell.

Oncogenes

Mutated or overexpressed proto-oncogenes that drive unregulated cell proliferation and block apoptosis; requiring only a single mutated allele to exert dominant effect.

Tumor Suppressor Genes

Genes that normally constrain the cell cycle, repair DNA damage, and trigger apoptosis; both alleles must be inactivated for neoplastic transformation to occur.

p53 Gene

A tumor suppressor gene on chromosome 17 that halts the cell cycle to allow DNA repair or triggers apoptosis; mutated in Li-Fraumeni syndrome.

Rb Gene

A tumor suppressor gene located on chromosome 13 that regulates cell cycle progression; mutations predispose individuals to retinoblastoma and osteosarcoma.

BRCA1 and BRCA2

Tumor suppressor genes involved in DNA repair; mutations elevate the lifetime risk of developing breast cancer to 45–55% and increase ovarian cancer risk by 10 to 30 times.

Caretaker Genes

Genes (also referred to as mutator genes) responsible for maintaining genomic stability by encoding enzymes that repair DNA damaged during mitosis, chemical exposure, or irradiation.

Cellular Immortality

A hallmark of neoplastic cells characterized by the reactivation of telomerase, preventing telomere erosion and enabling infinite mitotic cycles.

Tumor Angiogenesis

The formation of new vascular networks induced by neoplasms through factors such as matrix metalloproteinases (MMPs) to supply nutrients and facilitate spread.

Anaplasia

The irreversible loss of cellular differentiation characterized by pleomorphism, high nuclear-to-cytoplasmic ratios, and atypical mitotic figures.

Direct Extension

Local invasion in which tumor cells degrade connective tissue boundaries and extracellular matrix via enzymatic secretions to infiltrate neighboring tissues.

Seeding

A route of neoplastic dissemination specific to peritoneal and pleural cavities or biopsy tracts, where tumor cells detach, spread across serous fluid, and implant on organ surfaces.

Paraneoplastic Syndromes

Systemic disorders resulting from substances (such as ectopic hormones or cytokines) secreted by a tumor that cause signs and symptoms distant from the primary site.

Cachexia

Severe wasting syndrome seen in advanced malignancies, driven by elevated metabolic rates, anorexia, and cytokines like TNF that degrade adipose and muscle reserves.

Tumor Grading

Histopathological evaluation measuring the degree of anaplasia and loss of tissue differentiation within a tumor, graded from Grade I (well differentiated) to Grade IV (undifferentiated).

TNM Staging System

A clinical classification schema evaluating cancer extent by assessing primary tumor dimensions and invasiveness (T), regional lymph node involvement (N), and distant metastasis (M).

Neoadjuvant Chemotherapy

Antineoplastic medical treatment administered before primary surgical resection to shrink tumor burden and suppress micrometastases.

Adjuvant Chemotherapy

Chemotherapy administered following surgical excision of a neoplasm to eradicate any occult residual tumor cells and prevent metastatic recurrence.