Infectious Diseases and Microbes - Vocabulary Flashcards (Lecture Notes)

Vocabulary flashcards covering key terms and definitions related to microbial pathogenesis, microbiome, and routes of transmission from the lecture notes.

Prion

Abnormal forms of a protein (PRP) that cause transmissible spongiform encephalopathies (TSEs); disease arises when the prion protein changes structure, altering its function.

Transmissible Spongiform Encephalopathy (TSE)

Group of neurodegenerative diseases caused by misfolded prion proteins affecting humans and animals.

PRP (prion protein)

Normal neuronal protein that becomes pathogenic when it misfolds, leading to prion diseases.

Prion transmission routes

Can be transmitted via surgical instruments, organ transplantation, blood transfusion; also associated with cannibalism and mad cow disease exposure.

Virus

Obligate intracellular parasite that requires a host cell to replicate; comprised of nucleic acid genome, a capsid, and sometimes a lipid envelope.

Virus genome classification

Viruses are classified by whether their genome is DNA or RNA (not both).

Capsid

Protein coat surrounding a virus’s nucleic acid genome.

Envelope (viral)

Lipid membrane surrounding some viruses, derived from host membranes during budding.

Viral nucleic acid genome

DNA or RNA that carries the viral genetic information (not both in the same virion).

Bacteria

Prokaryotic organisms with no membrane-bound nucleus; often have peptidoglycan in their cell wall; may have flagella or pili.

Peptidoglycan

Long sugar chains forming the bacterial cell wall; thicker in gram-positive bacteria, thinner in gram-negative bacteria.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer that retains crystal violet stain and lacks an outer membrane.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides; stains differently and often more antibiotic-resistant due to outer membrane.

Pili

Surface projections that allow bacterial attachment to host cells.

Flagella

Tail-like structures that enable bacterial motility.

Nucleoid

Region in prokaryotes where the chromosome is located; not a true nucleus.

Fungi

Eukaryotic microbes with thick cell walls; can cause superficial or deep infections; include endemic and opportunistic species.

Endemic fungi

Invasive fungi geographically restricted to particular regions (e.g., valley fever in the Southwestern U.S.; Histoplasma in the Ohio River Valley).

Opportunistic fungi

Fungi that typically colonize hosts but cause disease primarily in immunocompromised individuals.

Protozoa

Single-celled eukaryotic parasites that can cause disease (e.g., Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis, Toxoplasma gondii).

Giardia lamblia

Protozoan causing giardiasis via contaminated water; intestinal infection.

Entamoeba histolytica

Protozoan causing amebiasis/intestinal infection.

Trichomonas vaginalis

Protozoan transmitted sexually; commonly infects the genital tract; has flagella.

Toxoplasma gondii

Protozoan acquired from cats or undercooked meat; causes toxoplasmosis.

Helminths

Parasitic worms (roundworms, tapeworms, flukes) with complex life cycles; disease severity often relates to parasite burden.

Roundworms, tapeworms, and flukes

The three major groups of helminths causing human infections.

Ectoparasites

Arthropods like lice, bed bugs, fleas (insects) and mites, ticks (arachnids) that bite or live on the skin; can be vectors for pathogens (e.g., Borrelia burgdorferi/Lyme disease).

Microbiome

Diverse population of bacteria, fungi, and viruses in and on the human body; important for digestion, barrier function, and immune regulation.

Dysbiosis

Alteration of the microbiome composition associated with disease; can be caused by antibiotics, low diversity, or inflammatory bowel disease.

Inflammatory bowel disease (IBD)

Autoimmune conditions like Crohn’s disease and ulcerative colitis with altered gut microbiota and reduced microbial diversity; different from IBS (functional).

Norovirus

Highly contagious, hardy virus that can persist on surfaces for long periods; infectious dose can be very small (as low as 10 viral particles).

Emerging and reemerging infectious diseases

New pathogens or previously known pathogens increasing in prevalence due to detection methods, zoonoses, virulence gene acquisition, immune suppression, and human behavior.

Routes of microbial entry

Pathogens can enter via skin, gastrointestinal tract, respiratory tract, or urogenital tract; vertical transmission from mother to fetus is also possible.

Transmission methods

Direct/indirect contact, respiratory droplets, aerosols, stool, urine, genital tract, rectal/oral routes, and vertical transmission.

Pathogenesis mechanisms

Infection can cause tissue damage by direct cell entry, toxin production, or immune-mediated collateral damage.

Urinary tract infections (UTIs)

Infections entering via the urethra; more common in women due to shorter urethra; can ascend to kidney (pyelonephritis).

Skin as barrier

The skin functions as the first physical barrier to infection, protecting against microbial invasion.

Antibiotics and normal flora

Broad-spectrum antibiotics can disrupt normal flora, leading to overgrowth of Candida and Clostridium difficile.

Vertical transmission

Transmission of pathogens from mother or birthing person to fetus or newborn across the placenta or during birth.

Viral vs bacterial injury

Viruses typically cause disease by direct cellular damage through replication; bacteria can adhere to/invade tissues and may produce toxins.