Parasites, Fungi, Bacteria, and Viruses Flashcards

Flashcards for reviewing lecture notes on parasites, fungi, bacteria, and viruses.

Parasite (vs. Virus/Bacteria/Fungi)

Eukaryotic cell type; Larger size; Large, linear chromosomes; Asexual or sexual reproduction; Classified as Protista (protozoa) or Animalia (helminths)

Protozoa

Single-celled, often motile, microscopic parasites (e.g., Giardia, Plasmodium)

Helminths

Multicellular worm parasites (e.g., Ascaris, Schistosoma)

Tropism (Parasites)

Classification of parasites based on the site they infect: intestinal, tissue, blood.

Protozoa Life Stages

Cyst, trophozoite, oocyst

Helminth Life Stages

Egg, larva, adult

Protozoa Reproduction

Mostly asexual; Transmission often via cysts/oocysts

Helminth Reproduction

Mostly sexual (M/F worms); Transmission often via ingestion, skin

Multi-Species Lifecycles (Parasites)

Parasites may need 2+ different hosts to complete their life cycle (e.g., snails, cats, humans).

Hygiene Hypothesis

Lack of early parasite exposure may lead to immune imbalance, contributing to allergies and autoimmune diseases.

Immune Response to Helminths

Th2 response: IgE, eosinophils, mast cells

Immune Response to Intracellular Protozoa

Th1 response (e.g., Toxoplasma)

Parasite Diagnosis

Stool microscopy (eggs, cysts, trophozoites), serology (antibodies or antigens), PCR, imaging, tape test (pinworms)

Challenges in Treating Parasites

Parasites are eukaryotic, so fewer drug targets; treatment often requires longer courses, has greater toxicity risks, and must be species-specific

Antiprotozoals

Target DNA, protein, folate synthesis; used for Plasmodium, Giardia

Anthelmintics

Target neuromuscular system, glucose uptake; used for Ascaris, Hookworm

Neglected Tropical Diseases (NTDs)

Group of 20+ parasitic, bacterial, and viral diseases affecting 1+ billion people in poor, tropical areas; often chronic, disabling, underfunded, and reinforce poverty.

Protozoa (Definition)

Unicellular, eukaryotic parasites that can live in water, soil, or inside hosts; reproduce mainly by asexual binary fission.

Amoebas

Protozoa that move via pseudopodia (e.g., Entamoeba histolytica)

Flagellates

Protozoa that move via flagella (e.g., Giardia, Trypanosoma)

Ciliates

Protozoa that move via cilia (e.g., Balantidium coli)

Apicomplexa

Non-motile protozoa; use gliding (complex life cycle) (e.g., Plasmodium, Toxoplasma)

Cyst

Dormant, thick-walled stage of protozoa; survives harsh conditions; infective form (e.g., Giardia)

Oocyst

Zygote enclosed in a cyst wall (Apicomplexa); formed after sexual reproduction; sheds in feces (Toxoplasma, Cryptosporidium)

Trophozoite

Active, feeding, motile form of protozoa; causes tissue damage during infection

Intestinal Protozoa

Affect GI tract (e.g., Giardia, Entamoeba, Cryptosporidium); cause diarrhea, cramps, malabsorption

Tissue Protozoa

Affect muscles, brain, eye (e.g., Toxoplasma, Trichinella); cause encephalitis, chorioretinitis

Blood Protozoa

Affect blood, RBCs (e.g., Plasmodium (malaria), Trypanosoma, Babesia); cause fever, anemia, neurologic signs

Sickle Cell Trait

Heterozygous; provides protection against malaria (Plasmodium falciparum)

Sickle Cell Disease

Homozygous; harmful genetic condition causing pain, anemia, organ damage

Nematodes (Roundworms)

Cylindrical, unsegmented helminths (e.g., Ascaris, Pinworm, Hookworm, Trichinella, Filariae)

Cestodes (Tapeworms)

Flat, segmented helminths (e.g., Taenia solium)

Trematodes (Flukes)

Flat, leaf-shaped, unsegmented helminths (e.g., Schistosomes)

Ascaris lumbricoides

Roundworm; transmission via ingestion of eggs; causes pneumonia, bowel obstruction; diagnose with eggs in stool; treat with anthelmintics

Enterobius vermicularis (Pinworm)

Transmission via anal-oral route; causes anal itching; diagnose with tape test; treat with anthelmintics

Hookworms

Transmission via skin penetration; causes iron-deficiency anemia, growth delay; diagnose with eggs in stool; treat with anthelmintics

Trichinella spiralis

Transmission via undercooked pork; causes myalgia, inflammation, cardiac/CNS issues; diagnose with serology, biopsy; treat with antiparasitics only effective on adult stage

Taenia solium (Pork Tapeworm)

Transmission via undercooked pork; may be asymptomatic or cause neurocysticercosis; diagnose with brain imaging; treat with antiparasitics + steroids

Filariae

Transmission via vector bites; cause river blindness (Onchocerca) or elephantiasis (Wuchereria); diagnose with blood smear, skin snip; treat with antiparasitics

Schistosomes (Trematodes)

Transmission via skin contact with water; cause granulomas, fibrosis, organ damage; diagnose with eggs in stool/urine, serology; treat with praziquantel

Ova (Medical Terminology)

Eggs of helminths

Worm Burden

Number of adult worms in a host; correlates with disease severity

Cercariae

Infective larval form of trematodes released by snails

Granuloma

Inflammatory mass formed around persistent parasite eggs

Hypereosinophilia

Elevated eosinophil count, often in response to parasitic infection

Autoinfection

When a parasite reinfects the same host (e.g., pinworm)

Neurocysticercosis

Brain infection by Taenia solium cysts

Unique Features of Fungi

Eukaryotic, cell walls made of chitin, ergosterol in cell membranes, reproduce by spores, dimorphic capability (yeast

Mycoses

Fungal infections; classified by location and host status

Endemic Mycoses

Geographic, affect healthy hosts (Histoplasma, Coccidioides)

Opportunistic Mycoses

Affect immunocompromised only (Candida, Cryptococcus, Aspergillus)

Subcutaneous Mycoses

Beneath skin, enter via trauma (Sporothrix, Mycetomas)

Superficial Mycoses

Outer skin, hair shaft (Malassezia)

Cutaneous Mycoses

Infect keratinized skin/hair/nails (Dermatophytes)

Diagnosis of Mycoses

Microscopy, culture, serology, PCR

Polyenes (Antifungals)

Bind ergosterol -> pore formation (Amphotericin B)

Azoles (Antifungals)

Inhibit ergosterol synthesis (Fluconazole, itraconazole)

Echinocandins (Antifungals)

Inhibit β-glucan synthesis (cell wall) (Caspofungin)

Histoplasma capsulatum

Location: Ohio & Mississippi River Valleys; causes mild respiratory to disseminated disease; diagnose with antigen test, culture; treat with Itraconazole

Blastomyces dermatitidis

Location: Great Lakes, Mississippi & Ohio River Valleys; causes pulmonary infection, cutaneous ulcers, bone lesions; diagnose with culture, microscopy; treat with Itraconazole

Coccidioides immitis/posadasii

Location: Southwestern U.S.; causes flu-like illness, can disseminate to skin, joints, CNS; diagnose with serology, culture; treat with Fluconazole

Candida albicans

Normal flora that overgrows with immune suppression; causes thrush, diaper rash, vaginal yeast infection; diagnose with culture, KOH prep; treat with topical azoles

Cryptococcus neoformans

Found in pigeon droppings; causes pulmonary infection -> meningitis in AIDS patients; diagnose with India ink stain, cryptococcal antigen test; treat with Amphotericin B

Aspergillus fumigatus

Ubiquitous mold; causes invasive aspergillosis (lungs, brain), fungus balls; diagnose with biopsy, CT scan, galactomannan test; treat with Voriconazole

Pneumocystis jiroveci (PCP)

Atypical fungus; causes severe pneumonia in AIDS patients; diagnose with silver stain; treat with TMP-SMX

Malassezia spp.

Part of normal skin flora; causes folliculitis when overgrown; diagnose with skin scraping, KOH prep; treat with topical antifungals

Sporothrix schenckii

Mold in environment, enters skin to become yeast; causes painless ulcer spreading along lymphatics; diagnose with culture or biopsy; treat with Itraconazole

Stachybotrys chartarum (Black Mold)

Grows in damp, cellulose-rich environments; produces mycotoxins; linked to respiratory symptoms

Antony van Leeuwenhoek

Invented microscope; first to observe microbes

Edward Jenner

Created first vaccine (smallpox)

Ignaz Semmelweis

Linked handwashing to decreased infection in childbirth

Louis Pasteur

Disproved spontaneous generation, developed pasteurization and vaccines

Joseph Lister

Pioneered antiseptic surgery

Robert Koch

Linked microbes to disease (Koch’s postulates); founder of bacteriology

Florence Nightingale

Revolutionized hygiene and hospital reform

John Snow

Traced cholera to contaminated water; founder of epidemiology

Germ Theory

The idea that microorganisms cause disease

Koch's Postulates

Framework to link a specific microbe to a disease: found in all diseased individuals, can be isolated and grown in pure culture, causes disease when introduced into a healthy host, re-isolated from the experimentally infected host.

Steps in the Infection Framework

Entry, attachment, immune evasion, nutrient acquisition & growth, replication, damage, exit/transmission

Components of the Immune System

Physical barriers, microbiota, innate immunity, adaptive immunity

Diagnostic Strategies for Pathogens

Microscopy, culture, serology, nucleic acids (PCR)

Features of a Virus

Nucleic acid genome, capsid, envelope (optional), enzymes (optional)

Baltimore Classification System (Viruses)

Based on genome type and method of replication (DNA vs RNA, single- vs double-stranded, positive- vs negative-sense RNA, reverse transcription)

Viral Replication Cycle

Attachment, entry, uncoating, replication, protein synthesis, assembly, release

Routes of Viral Entry

Respiratory tract, gastrointestinal tract, sexual contact, bloodborne, zoonotic or vector-borne

Viral Diagnostics

PCR, ELISA or antigen tests, serology, viral culture

One Health

Integration of human, animal, and environmental health

Prions

Infectious proteins that cause neurodegenerative diseases by misfolding other proteins

Features of Bacteria

Prokaryotic, single-celled, lack nucleus and membrane-bound organelles, DNA genome, reproduce via binary fission

Gram Stain

Classification of bacteria based on cell wall structure: Gram-positive (thick peptidoglycan, purple stain) vs. Gram-negative (thin wall, outer membrane, pink stain)

Commensal Uses of Bacteria

Gut flora aid digestion, immune training

Commercial Uses of Bacteria

Yogurt, cheese, probiotics, waste treatment

Scientific Uses of Bacteria

Genetic engineering, antibiotic production, research models

Antibiotics

Natural or synthetic drugs that kill or inhibit bacteria

Major Antibiotic Targets

Cell wall synthesis, protein synthesis, DNA/RNA synthesis, metabolic pathways

Antimicrobial Resistance (AMR)

Bacteria acquire the ability to survive antibiotics that once killed them

Horizontal Gene Transfer (Bacteria)

Conjugation (plasmid transfer), transformation (DNA uptake), transduction (bacteriophage-mediated)