Intro to Life Sciences Module 2: Microorganisms Study Guide
Pathogen: a microbe whose relationship with its host is parasitic and results in infection and disease.
Pathogenicity: an organism’s potential to cause a disease
True pathogens: capable of causing a disease in normal immune defences and healthy people
Opportunistic pathogens: causing a disease when peoples immune defences are compromised and when a pathogen travels to a part of a body that is not natural.
Virulence: the severity of a disease by a particular microbe
It is determined by creating itself in a host and causing some sort of damage
Virulence Factor: any characteristic or structure of a microbe that contributes to the ability to cause damage and implement itself in a host.
Severe enzymes can disrupt the immune system to make
it easier to travel in host
Polymicrobial Infections: infections that have multiple organisms in the site
Eg. Influenza infections lead to pneumonia
Primary and secondary infections can both happen in the same site
Wound cultures sometimes show flora (bacteria in our part of body), meaning there is all types of bacterias in humans but they are not all pathogens
Only one type of bacteria is identified and the cause of one infection
Lots of pathogens live in our bodies but doesn't cause infections
Chain of Infection:
Agent: germs (bacteria, viruses, parasites)
Reservoir: where the germs live (people, animals, soil, water, foods)
Portal of exit: how bacteria get out (mouth, cuts in skin, washrooms)
Mode of transmission: contact, droplets through coughing and sneezing)
Portal of entry: how germs get in (mouth, cuts on skin, eyes)
Susceptible Host: through another sick person (babies, elderly, unimmunized people)
Disinfection: The process of destroying pathogens through heat or chemicals (bleach)
Sanitation: reducing the microbial population to safe levels, clean condition, removing waste. (detergent)
Sterilization: Complete destruction of all forms of microbial life (chemicals, radiation)
Antiseptosis: Removing pathogens from living tissue (alcohol)
Degerming: removing microbes from a limited area (Soap)
Portals of Entry
1. skin
2. Gastrointestinal tract
3. Respiratory tract
4. Urogenital tract
How can we reduce infections from spreading?- washing hands (the most effective)
7 types of infections
Localized Infection
Systematic Infection
Mixed Infection
Primary Infection
Secondary Infection
Acute Infection
Chronic Infection
Localized Infection: microbes enter the body and remain confined to a specific tissue
Systematic Infection: an infection throughout the body
Mixed Infection: several agents establish themselves simultaneously at the infection site
Primary infection: initial infection
Secondary Infection: another infection by a different microbe
Acute Infection: comes on rapidly, with severe but short-lived effects
Chronic infection: progress and persist over a long period of time
What are three ways that microorganisms cause damage to their host?
1. directly through toxin
2. indirectly inducing hosts defences
3. epigenetic changes to host cells by microbes
Toxin: a specific chemical product of microbes that is poisonous to other organisms
Neurotoxins act on the nervous system.
Enterotoxins act on the intestine
Hemotoxins lyse red blood cells
Nephrotoxins damage the kidneys
Exotoxins: toxic substances that bacteria secrete into their environment
Endotoxin: a toxin that is present inside a bacterial cell and is released when the cell disintegrates
Portals of Exit: Pathway for pathogens to leave the host.
Exit through secretions, excretions, discharges, or sloughed tissue.
Examples:
Respiratory droplets (cough, sneeze)
Blood, saliva, semen, vaginal fluids
Feces or urine
Pus or skin flakes from wounds
More microbes = higher chance of spread.
Usually the same as the portal of entry (e.g., respiratory tract).
Can be different in some cases (e.g., enters by needle stick, exits by blood).
What are the different ways that infections exit? (6)
coughing/ sneezing
insect bite
removal of blood
feces
urine
skin cells
Incubation period: no symptoms, starting to replicate
prodromal stage: symptoms begin to appear (sore throat, fatigue, nausea)
height of infection: symptoms level off
convalescent period: recovery from the infection
continuation period: only some diseases have this period when pathogen or symptoms linger for the prolonged period of time
How long does it take to feel better from an infection?- 5-7 days
What are the five common hospital pathogens?
1. Clostridioides (GI infections)
2. Staphylococcus aureus (pneumonia)
3. Klebsiella (surgical site infections)
4. Escherichia coli ( surgical site infections)
5. Enterococcus Species
What are the worse infections?- infections that are most resistant, and most verbulant
Bactericide: substance that kills bacteria
Fungicide: substance that kills fungi or inhibits their growth
Virucide: inactivates viruses
Sporicide: capable of killing endospores
Germicide: chemical agent that kills microorganisms
Sepsis: the growth of microorganisms in blood/other tissues overwhelming host response
Asepsis: any practice that prevents the entry of infectious agents into sterile tissues and thus prevents infection
Antisepsis: chemical agents exposed to skin membranes through wounds, and surgical incisions
Preparing the skin before surgical incisions with iodine compounds
Swabbing an open root canal with hydrogen peroxide
Ordinary hand washing with a germicidal soap
What is the effect of chemical agents on the cell wall?- They block and damage the cell wall.
How do chemical agents affect the cytoplasmic membrane?- They disrupt the lipid layer, causing it to open.
What is the impact of chemical agents on cellular synthesis?- They interrupt protein synthesis through ribosomes and growth.
How do chemical agents affect proteins in cells?- They attach to the active site, causing denaturation.
Interactions Between Drugs and Microbes
Goal of Antimicrobial Drugs:
Stop or break normal functions in germs (bacteria, fungi, protozoa).
Stop viruses from making more copies of themselves.
Block important enzymes germs need to grow or build cell parts.
Break down or destroy parts of the germ’s cell.
Be selective — kill the germs without hurting human cells.
Antimicrobial Resistance
Drug resistance means germs adapt and can survive doses of medicine that used to kill them.
This happens because microbes are genetically flexible and can change or share genes.
Resistance can be:
Intrinsic: naturally built-in.
Acquired: developed over time.
Microbes can become resistant by:
Mutating (changing their DNA).
Getting new genes from other microbes (gene sharing).
Slowing or stopping metabolism, so the antibiotic can’t affect them (these are called “persisters”).
Antibiotics Resistance
Few new antibiotics are being made.
Drug companies earn less from antibiotics, so they focus on other medicines.
Developing new antibiotics takes a lot of time and money
So high in resistance, where the infection cannot be treated
Gram-Positive (G+)
Staphylococcus aureus – skin bacteria; includes MRSA (hard to treat) and MSSA (easier to treat).
Streptococcus – causes throat and skin infections; some strains become resistant.
C. diff (Clostridia) – causes severe diarrhea after antibiotic use.
Gram-Negative (G–)
E. coli & Klebsiella – gut bacteria; some make ESBL, making them resistant.
Pseudomonas – hard to kill; forms green, smelly biofilm.
Neisseria gonorrhoeae – causes gonorrhea; becoming drug resistant.
Campylobacter – common cause of food poisoning.
Epidemiology
The study of how often and where diseases happen in specific populations.
Uses many fields: microbiology, medicine, psychology, sociology, ecology, statistics, and more.
Look at all types of diseases, including heart disease, cancer, addictions, and mental health issues.
Germ Theory: The theory that infectious diseases are caused by certain microbes (how it is closed by the environment)
Father of Epidemiology: John Snow
Studied a cholera outbreak in London, 1854.
Hypothesized that cholera spread through contaminated water (feces).
Collected data: talked to residents, mapped deaths.
Found the Broad Street water pump was the source.
Removed the pump handle → cholera cases stopped.
Florence Nightingale
Modern nursing (germ) theory
Used methods in military, hospitals, schools
Promoted clean healthcare and sanitation by hygiene.
e.g separating waste, cleaning floors, unclogging sewage pipes
More men died of disease than traumatic injuries
Prevalence: Total number of existing cases in a given population.
Incidence: the number of new cases over a certain time period
Morbidity: the number of cases of disease and how widespread the disease is
Mortality: measures total number of death rates
common source epidemic: result from common exposure to a single source of infection over a period of time
point source epidemic: one in which the infectious agents came from a single source
propagated epidemic: results from an infectious agent that is communicable from person to person and is sustained over time in a population
index case: first case in an epidemic
Endemic: confined to a particular country or area
Sporadic: occurring irregularly
Epidemic: A widespread outbreak of an infectious disease.
Pandemic: spread of an epidemic across continents
Microorganisms: study of all living organisms that are too small to be seen by the naked eye
Organisms reproduce rapidly and can be tested in labs and examinations (staining, microscopes, and cultures)
We classify microbes by taxonomy, nomenclature, classification and identification
Taxonomy: the science of how we classify, name and describe all living things
Developed in 1700s by Linnaeus and is improved overtime
We use different methods to identify organisms by DNA/RNA sequencing, antibody testing (effectiveness against protein
Name using genus and epithet (species) through the binomial system
Nomenclature: assessments through scientific names to categorize organisms in groups
Each organism has two names: Genus + Species (e.g., Escherichia coli).
Formatting:
Italicize
Underline
Abbreviate after first use: E. coli
Some microbes have strains: e.g., E. coli O157:H7 (caused Walkerton outbreak, 2000).
Campylobacter can also cause outbreaks.
Types of Microorganisms:
Prokaryotic
Eukaryotic
Helminths
Fungi
Viruses
Prokaryotic: (DNA not in a nucleus)
Two types: Bacteria and Archaea.
Difference:
Bacteria: cell walls made of peptidoglycan.
Archaea: cell walls made of other substances.
Archaea: not harmful to humans; live in extreme environments; help ecosystems.
Bacteria: mostly helpful; some (~5%) can cause disease.
Where they live: on/in humans, animals, plants, and the environment.
Normal flora / human microbiome: usual bacteria in/on our bodies; can be helpful or sometimes harmful.
Bacteria: single loop of DNA, extra genetic materials (plasmid)-> Plasmids can help bacteria survive, like making them resistant to antibiotics.
Bacterial cells mostly in humans, help fight against pathogenic bacteria
Reproduced in binary fission (DNA replicates splits into 2 daughter cells
Produces endospores in cytoplasm, resistant to heat, UV and disinfections
Endospores are classified through using negative stains.
Cell Structure:
Cytoplasmic membrane
Ribosomes
DNA not help in nucleus
Surrounded by a lipid membrane (bilayer).
Gram-positive: made of peptidoglycan. (composed of polymers NAM & NAG subunits)
Gram-negative: thin or no cell wall
Some bacteria can move or stick to other cells using:
Flagella: tail-like structures for movement.
Pili: tiny projections for attachment.(responsible for movement & binding to other cells)
Bacterial Cell Wall Types
Gram-positive: thick peptidoglycan layer + teichoic acid; simpler structure.
Gram-negative: thin peptidoglycan layer + outer membrane with lipopolysaccharides; more complex.
Staining: managing culture through blood to anticipate treatment
Bacteria Structure & Movement
Movement with Flagella:
How they move:
Chemotaxis: move toward or away from chemicals.
Magnetotaxis: move along magnetic fields.
Phototaxis: move toward or away from light.
Types of movement:
Run: flagella rotate counterclockwise → bacteria moves forward.
Tumble: flagella rotate clockwise → bacteria changes direction.
Biofilms
What they are:
Groups of bacteria that stick to a surface using glycocalyces.
Produce a protective slime (not a slime mold).
Why bacteria make them:
Protection from antibiotics and the immune system.
Access to nutrients and water.
Why it matters in healthcare:
Harder to treat infections → can cause superinfections.
Resistant to disinfectants and antibiotics.
Can form on:
Skin (chronic wounds)
Teeth (plaque)
Medical devices (surgical tools, prostheses)
Wounds in lower limbs take longer to heal due to less blood flow.
Removal: usually requires mechanical cleaning.
Bacterial Shapes
Transmission (TEM): using electrical beams that pass through species to visualize small images to see tissue sections and subcellular structures
Scanning (SEM): Uses electron beams to visualize surfaces can observe 3-d surface details on species
Bacterial Infections
Danger level: Can be mild to life-threatening; bacteria are everywhere.
Common symptoms:
Fever, chills
Pus or discharge
Fatigue, weakness
Low blood pressure, high heart rate
Types of infections:
Localized: stays in one area (e.g., cellulitis)
Systemic: spreads through the body (e.g., bacteremia)
Treatment:
Antibiotics based on the type of bacteria (Gram stain helps guide this)
Symptoms usually improve in 24–48 hours after starting treatment
Supportive care: Nursing, medical, and multidisciplinary care help recovery and comfort.
Introduction to Eukaryotes
Eukaryotic cells: have a nucleus.
Types: Protists, algae, protozoa.
Protists:
Any eukaryote that is not an animal, plant, or fungus.
Taxonomy is complicated because they don’t share a single origin.
Protozoa:
Non-photosynthetic, motile, always unicellular.
Can be free-living or parasitic.
Reproduce sexually, asexually, or both.
Algae:
Photosynthetic.
Can be unicellular or multicellular.
Some are free-living, some are attached to surfaces.
Protozoa
Often called “one-celled animals” or parasites.
Cell structure:
Surrounded by a plasma membrane (plasmalemma).
Some have a pellicle (rigid structure for support).
Some have cytosomes for feeding (phagocytosis).
Some have flagella or cilia for movement.
Contain various organelles
Protozoal Infections
Common symptoms:
Fatigue, abdominal pain, fever
Diarrhea, fatty stools, nausea, vomiting, gas
Weight loss
Treatment:
Some antibiotics or antiprotozoal drugs
Chemotherapy in certain cases
Malaria: treatable; travelers to high-risk areas may take preventive drugs (chemoprophylaxis)
Infection patterns:
Can be remitting-relapsing (cycles of illness), but rare in Canada.
Helminths (Worm Infections)
Why studied in microbiology: early life stages are microscopic.
Two main types:
Roundworms (Nematoda)
Tapeworms (Platyhelminthes)
Characteristics:
Have full organ systems (they are animals).
Can have male, female, or both reproductive organs.
Pathogenicity:
Not all worms infect humans, but those that do act as parasites.
Nematodes(soil contamination):
Transmitted through contaminated soil
Common in warm and damp climates
Live in intestine and eggs passed by poop
Impairs nutritional needs (malabsorption)
Hygiene and food prep is key
Platyhelminthes:
Flukes, Tapeworms, and Turbellarians
Flukes and tapeworms: can infect humans; turbellarians generally do not.
Flukes:
Cause rare gastrointestinal infections.
Use an oral sucker to attach to lungs, liver, intestines, or large blood vessels.
Tapeworms:
Attach to the small intestine using suckers or hooks.
Have segmented bodies; segments can detach to reproduce.
Infections are rare.
Treatment:
Usually antiparasitic drugs (sometimes chemotherapy).
Endoscopy is rarely needed.
Uncommon in urban North America; more common where sanitation is poor.
Diagnosis: usually with a stool test.
Treatment:
Anti-helminth drugs kill the worms over several days.
Symptomatic care is also important.
Symptoms:
Often non-specific.
GI symptoms are most common (worms live in intestines).
If worms infect other organs, symptoms will vary.
Ivermectin has been used for helminths
Fungi:
Can be microscopic (yeast) or macroscopic (mushrooms, molds).
Yeast = unicellular, Mold = multicellular.
Some diseases (pathogenic) → fungal infections are called mycoses.
Found in the environment, in healthcare settings, or as opportunistic infections (in people with weak immune systems).
Structure & Growth
Cell walls contain chitin (like insects, not plants).
Have ergosterol instead of cholesterol — this is the target of antifungal drugs.
Most get energy from dead organic matter (decomposers).
Rarely parasitic.
Made up of hyphae (filaments) that form a network called mycelium — the fuzzy part of mold.
Some yeast form pseudohyphae (chains of cells).
Reproduction
Asexual: budding, fragmentation, or spore formation by mitosis.
Sexual: involves meiosis and spore formation; may be self- or cross-fertilizing.
Mushrooms (basidiomycetes) reproduce only sexually.
Types & Examples
Yeast:
Reproduce by budding.
Can cause infections such as:
Oral thrush
Vaginal yeast infection (candidiasis)
Skin candidiasis (dermatitis)
Blood infections (invasive candidiasis)
Benefits of Fungi
Food: mushrooms, bread, beer, wine.
Decomposition: break down dead matter, enrich soil.
Medicine: produce antibiotics, vitamins, and alcohols.
Research & therapy: Psilocybin (from “magic mushrooms”) is studied for mood and anxiety treatment.
Negative Impacts
Spoil food and damage crops.
Destroy wood/timber and homes with mold after floods or moisture damage.
Fungal Infections – Symptoms
Lungs: cough, chest pain, fever, joint pain, coughing blood.
Skin: rashes, lesions, itching.
Mouth: white patches, pain, trouble swallowing, loss of taste.
Genital area: itching, pain, discharge.
General (systemic): fever, nausea, fatigue, weight loss.
Treatment
Antifungal drugs (type depends on infection):
Topical: creams or ointments.
Oral: pills or liquids.
IV (intravenous): for severe infections.
Introduction to Viruses
Acellular — not made of cells (unlike bacteria or fungi).
Smallest microorganisms — visible only under an electron microscope.
Ubiquitous — found everywhere in nature.
Contain surface molecules (spikes) that allow them to attach to specific host cells.
Can be active or inactive depending on if they are infecting a host.
Obligate intracellular parasites → must use a host cell to reproduce.
Have significantly influenced evolution of all life forms.
Viral Structure
Capsid: Protein shell that surrounds the genome.
Envelope: Some viruses have a lipid membrane taken from the host cell.
Spikes: Surface proteins that help with attachment to host cells.
Virion: A fully formed virus that is capable of causing infection.
Viral Genome (Genetic Material)
Can contain DNA or RNA, never both.
DNA viruses:
Can be single-stranded (ss) or double-stranded (ds); may be linear or circular.
RNA viruses:
Usually single-stranded (sometimes double).
Positive-sense (+) RNA: ready for immediate translation.
Negative-sense (–) RNA: must first be converted into positive-sense RNA before translation.
Segmented genomes: genes split across multiple RNA pieces.
Retroviruses: carry enzymes to make DNA from RNA (reverse transcriptase → e.g. HIV).
Classification of Viruses (Baltimore System)
Previously classified by host or disease.
Now classified by genome type and replication method.
1. dsDNA, enveloped
2. dsDNA, naked
3. ssDNA, naked
4. dsRNA naked
5. +ssRNA, naked
6. +ssRNA, enveloped
7. -ssRNA, enveloped
Positive - positive sense strand
Negative - negative sense strand (needs to be converted transcription before translation)
DNA Viruses:
Double-stranded (dsDNA):
Variola virus → Smallpox
Herpes simplex II → Genital herpes
Single-stranded (ssDNA):
Parvovirus → Erythema infectiosum (skin rash)
RNA Viruses:
Single-stranded (+ sense):
Poliovirus → Poliomyelitis
Single-stranded (− sense):
Influenza virus → Influenza (flu)
Double-stranded (dsRNA):
Rotavirus → Gastroenteritis (stomach flu)
Single-stranded RNA + reverse transcriptase:
HIV → AIDS
Viral Transmission:
Direct contact: person-to-person (touch, saliva, blood).
Indirect contact: touching contaminated surfaces (fomites).
Mechanical vector: virus carried on an organism’s body (e.g., fly).
Biological vector: virus carried inside a vector and spread by bite (e.g., mosquito, tick).
Viral Life Cycle:
Virus enters cells by endocytosis or membrane fusion.
Nucleic acid replicates inside the host cell.
New virions (virus particles) are formed.
Virions are released from the host cell.
Some viruses go latent (dormant) — can reactivate later (e.g., chickenpox → shingles).
Viral Cultures:
Used to find and identify viruses.
Viruses must be isolated (by filtration or centrifugation).
Grown in:
In vivo: inside a living organism.
In vitro: inside lab-grown cells.
Tests are virus-specific (e.g., COVID, flu, RSV).
Viroids, Virusoids & Prions:
Viroids: small RNA; infect plants.
Virusoids: RNA needing helper virus; infect plants.
Prions: misfolded proteins; infect brains.
Cause other proteins to misfold → brain damage.
Example: Mad Cow / Creutzfeldt-Jakob disease.
Always fatal.
Clinical Significance & Treatment:
Symptoms depend on the infection site.
Most viral illnesses are self-limiting.
Supportive care: fluids, rest, fever + nausea meds.
Antivirals: used only in specific cases.
Vaccination: best prevention.
Examples: Ebola, COVID-19, Zika.
Viruses can weaken the immune system, increasing infection risk.
Nonspecific innate immunity: first line of defence in infections by blocking entry of microbes and targeting them for removal from body (basic form of nonspecific defences)
Keeps physical barriers to microbes (clears mucous)
The microbiome measures through physical protection against disease
Good germs in our body fight bad germs for food and space, so they help stop infections.
Physical Defences:
Physical barriers
Mechanical actions that remove microbes and debris
The microbiome
inhibits growth of pathogens
Microbes:
Dead skin and mucus trap germs.
The body removes them by:
Shedding skin, coughing, sneezing, urinating, crying (tears), or digestive movement (peristalsis).
These actions flush out pathogens from the body.
Normal Gut Microbes (Microbiome)
Help keep the gut healthy.
Train the immune system and help T-cells and B-cells fight infections.
Some microbes can cause problems if the immune system is weak or the gut is unbalanced.
Too much fluid loss (like in diarrhea or malnutrition) can wash out good bacteria.
In Children
Babies have an immature immune system.
They get some immunity from breast milk, which helps protect them early in life.
Built-In Body Defenses
Help protect the body from infections (like MRSA, which can cause serious infections).
Physical Barriers
Skin: blocks germs from entering.
Mucous membranes: line the digestive, urinary, respiratory tracts, and eyes.
Respiratory tract: traps and removes germs (coughing, mucus).
Genitourinary tract: flushed by urine and secretions to remove microbes.
When a Barrier Is Lost
Germs can enter the body and cause infections.
The body tries to compensate, but other organs work harder.
Bacteria may enter the bloodstream, leading to serious infection.
Chemical Defenses
The body makes natural chemicals to kill or slow germs.
Found in sebum (oil), saliva, mucus, stomach acid, urine, tears, earwax, and vaginal secretions.
These help wash away or destroy pathogens.
Antimicrobial Peptides (AMPs)
Tiny proteins made by the body when pathogens are detected.
Found on skin and other body areas.
Examples: dermcidin, cathelicidin, defensins, histatins, bacteriocins.
Function: attack and destroy harmful microbes.
Plasma (part of blood)
Contains proteins that help defend against infection:
Acute-phase proteins (respond to inflammation).
Complement proteins (help destroy microbes).
Cytokines (send signals to immune cells).
Complement System
Group of proteins in the blood that activate in sequence when microbes are detected.
Main actions:
Opsonization: marks germs so immune cells can destroy them.
Attracts white blood cells (chemoattraction).
Causes inflammation.
Forms the Membrane Attack Complex (MAC) → breaks open and kills microbes by disrupting their cell membranes.
Cytokines (Cell Communication Signals)
Chemical messengers that help cells communicate during immune responses.
Made by immune and body cells (like macrophages, lymphocytes, mast cells, etc.).
Functions:
Control inflammation and immunity.
Tell other cells when and how to respond to infection.
Trigger production of inflammation chemicals like histamine, prostaglandins, and acute-phase proteins.
Types of Cytokine Actions
Autocrine: acts on the same cell that released it.
Paracrine: acts on nearby cells.
Endocrine: travels in the blood to act on distant cells.
Main Idea
The complement system attacks and destroys microbes.
Cytokines help immune cells communicate, coordinate, and control inflammation.
Together, they form local chemical defenders against infection.
Inflammatory Response
Main idea:
The body’s natural reaction to injury or infection.
Can be local (one area) or systemic (whole body).
Chronic inflammation can lead to diseases like heart disease or worsen with poor diet or aging.
Classic Signs of Inflammation
Rubor (Redness): from increased blood flow to the area.
Calor (Warmth): from the extra heat carried by blood.
Tumor (Swelling): from fluid buildup in tissues.
Dolor (Pain): from nerve endings being triggered.
Loss of Function: sometimes occurs depending on the injury site.
What Causes Inflammation
Infection or trauma.
Tissue injury or death (necrosis).
Chemical damage.
Immune reactions (body fighting off pathogens).
Diapedesis:
WBCs (white blood cells) move out of blood vessels into tissues.
Blood vessels send signals to allow this movement.
WBCs can change shape to squeeze through vessel walls.
Endothelial cells help by grabbing and guiding WBCs out to the tissue.
Chemotaxis:
WBCs follow chemical signals to find infection or injury.
These chemicals “call” immune cells to the right spot.
Once there, WBCs attack pathogens and help healing
Inflammation Effects
Edema & Leaky Vessels (Swelling Benefits):
Extra fluid dilutes toxins.
Fibrin clots trap microbes to stop spread.
Neutrophils come to clean up bacteria, dead tissue, and debris.
Pus = dead cells + bacteria + fluid.
Pyogenic bacteria (like strep or staph) cause pus formation.
Fever
The body raises temperature to fight infection.
Heat slows down or kills some pathogens.
Less iron available for bacteria → they can’t grow.
Immune reactions speed up (WBC activity, phagocytosis, etc.).
Pyrogens (Cause Fever)
Exogenous (outside): from viruses, bacteria, fungi, vaccines, etc.
Endogenous (inside): from immune cells (e.g., interleukin-1, TNF).
Treating Fever
Mild fever = let it run, helps healing.
High or long fever = treat if risky (heart disease, seizures, etc.).
Side effects: fast heart rate, faster breathing, possible seizures.
The Blood
Main Parts:
Whole blood = blood cells + plasma
Plasma: yellowish fluid that carries cells and nutrients
Serum: plasma without clotting proteins (used for testing/treatments)
Blood Cell Production (Hematopoiesis):
Happens in the bone marrow
Stem cells make all new blood cells
Become red blood cells (carry oxygen)
White blood cells (WBCs) (fight infection)
Platelets (help blood clot)
White Blood Cells (Leukocytes):
Two main types:
Granulocytes – have visible grains when stained
Agranulocytes – no visible grains
Both types are key defenders in the immune system.
Neutrophils: leukocytes found in bloodstream and fight off infections (phagocytic)
Phagocytic Cells: absorb target cells
Immune System Basics
White blood cells (WBCs) move around the body looking for germs.
They recognize “self” cells (your own body) and attack “nonself” (foreign invaders).
Autoimmune diseases happen when the body accidentally attacks its own cells.
Antigens/markers on cell surfaces help identify what’s “self” or “foreign.”
Foreign cells are destroyed — most often through phagocytosis (WBCs “eat” them).
Mast Cells
Found in tissues (not the blood).
Part of the inflammatory response.
Release histamine, which causes swelling and mucus — epinephrine can counteract this in severe reactions (like allergies).
Natural Killer (NK) Cells
Kill virus-infected or cancerous cells.
Healthy cells show a marker called MHC — if it’s missing, NK cells attack.
Recognize abnormal cells by their low MHC and destroy them.
Lymph Nodes
Small, bean-shaped filters along lymphatic vessels.
Found in the neck, armpits, and groin.
Trap and filter pathogens.
Swollen lymph nodes mean the immune system is fighting an infection.
Spleen
Located in the upper-left abdomen.
Filters blood (not lymph).
Removes old red blood cells and pathogens.
Stores extra blood for emergencies (like bleeding).
Children without a spleen have weaker immune systems; adults usually cope fine.
Characteristics of Special Immunity:
Specificity: antibodies created specific to a pathogen
Memory: lymphocytes are programed to recall first time meeting the invader and rush to attack again
Red Bone Marrow
Found in flat bones and ends of long bones.
Makes blood cells (RBCs, WBCs, platelets).
B cells mature here → then migrate to lymph nodes, spleen, and other lymphoid tissues.
Thymus (T-Cell Maturation)
Located in the lower neck; triangle-shaped after fusion.
Naïve T cells develop specificity and mature here.
Mature T cells move to lymph nodes and spleen.
T Cells
Helper T cells: activate macrophages, B cells, and cytotoxic T cells.
Regulatory T cells: control immune responses, reduce inflammation.
Cytotoxic T cells: kill virus-infected cells, cancer cells, and foreign graft cells.
Do not make antibodies, but secrete cytokines to coordinate immunity.
B Cells
Develop in bone marrow, not directly cytotoxic.
Circulate as naïve lymphocytes → attach to antigens in lymph nodes, spleen, and other tissues.
Main function: produce antibodies when activated.
Primary vs Secondary Immune Response
Primary Response: first exposure to an antigen → slower, smaller response.
Secondary Response: repeat exposure → faster, stronger response (big spike in IgG).
Types of Immunity
1. Adaptive Immunity:
Natural: gained from normal exposure (e.g., had the infection).
Artificial: gained via medical procedures (vaccines, immune serum).
2. Active Immunity:
Your own B and T cells respond → make antibodies → create memory.
Can be natural or artificial.
3. Passive Immunity:
Receive antibodies from someone/something else.
Immediate protection but no memory.
MRSA: Methicillin Resistant Staphylococcus Aureus
Caused by S. aureus bacteria
Resistant to antibiotics
Site of infections: skin, lungs, blood
Causes bloodstream infections, pneumonia or surgical site of infections
Most common to spread in hospitals and communities
Opportunistic pathogens
Infections transmitted through skin contact
Symptoms: red swollen bumps, warm, full of pus.
Nasal and mouth swab test
Increases high risk symptoms
Treatments: decolonization, isolation, antibiotic therapy, drainage
Minimize exposure by washing hands and PPE, disinfecting/sanitation
Symptoms can vary on the person
C-Diff (Clostridium Difficile):
Rod shaped bacteria
Spread of exotoxins (spores make it easier to spread)
Gram-positive anaerobe creates 2 exotoxins
Disrupts skin and immune systems that causes infections
High severity cases cause range of infections
Inflammation in colon
Get treatment as soon as possible
Symptoms: mild diarrhea, loss of appetite, nausea, abdominal pain, mostly water fluid in stomach, sepsis, and death
Low BP, weight loss.
Treatments: Initial CDI episode 10 days, first CDI recurrence 20 days, subsequent CDI recurrence 25 days, fulminant CDI 30 days
Minimize exposure by soap and water or bleach
Meningitis:
inflammation , swelling, increase pressure on brain
Bacterial is more acute
Treatment through antibiotics or steroids from cerebrospinal fluid
Tested through lumbar parts in lab for infections
Infections -> bloodstream -> meninges
Avoid movements that cause cranial pressure
Symptoms: headache, vomiting, consciousness, visual changes
Can worsen by movements
Elevation of bed on head is key
Requires re-teaching in walking and treating small chronic conditions
Upper respiratory tract
Mouth
Nose
Nasal cavity
Sinuses
Throat
Epiglottis
Larynx
Lower respiratory tract
Trachea
Bronchi
Bronchioles
Alveoli
Whooping Cough (Pertussis)
Often in kids
Catarrhal stage: runny nose 1-2 weeks
Paroxysmal Stage: severe coughing several weeks
Convalescent phase: number of bacteria no symptoms
Pneumonia: inflammatory condition in the lung (fluid fills in alveoli)
Bacteria and fungi causes pneumonia
Can be deadly
Higher risk of getting it again
Physical therapy (deepening breathing and coughing exercises)
HIV Infection and AIDS:
HIV (Retrovirus)
Belongs to genus Lentivirus.
Retroviruses can cause cancer and serious, often fatal diseases.
Can alter the host’s DNA permanently.
Reverse Transcriptase (RT)
Enzyme that converts viral RNA into DNA.
This DNA can integrate into the host genome.
Effects on Host Cells
Viral genes are passed to new cells during replication.
Some retroviruses can transform cells, making them cancerous.
Can regulate certain host genes, affecting normal cell function.
Enveloped RNA Virus
Effects CD4 cells
Outer most layer (lipid envelope)
Membrane glycoprotein spikes absorption to the host cell
Only effects host cells that has CD4 marker and CCR-5
Use to gain entrance in tissue cells
Entry: HIV enters through mucous membranes or skin.
Targeting Dendritic Cells:
Travels to dendritic cells under the epithelium.
Virus replicates inside dendritic cells without killing them.
Amplification: Macrophages in skin, lymph nodes, bone marrow, and blood help the virus multiply.
Attacking Immune Cells: Destroys helper T4/CD4 cells, monocytes, macrophages, and B lymphocytes.
Cell Fusion: Virus binds to cell receptors and fuses cells together → forms syncytia, a hallmark of HIV infection.
HIV Prevention
Safe Sexual Practices:
Assume partners may be HIV-positive unless confirmed negative.
Use barrier protection (condoms) with partners of unknown status.
Avoid IV Drug Use:
Sharing needles can transmit HIV.
Prophylaxis:
Pre-exposure prophylaxis (PrEP): medication taken before exposure to prevent infection.
Post-exposure prophylaxis (PEP): medication taken after potential exposure to reduce infection risk.
Treatment:
No cure
New drug are improved overtime (improves quality of life)
Too poor for medications
Guidelines to notice exposure
Should be treated as soon as possible
Goals:
Improve and reduce HIV cases
Educate others on condition
Aerobic exercise reduces level of inflammation in HIV
Does not require PPE
Hepatitis:
Caused by several liver specific viruses
Progress to lung failure
Care through rest, fluids, medicines
Symptoms: fatigue and low blood pressure
Hepatitis A: contaminated by food, water (vaccine)
Hepatitis B: sexual intercourse, IV drug use (vaccine)
Hepatitis C: blood exposure, sexual intercourse (treatment)
Hepatitis D: blood contact sexual intercourse (no treatments)
Hepatitis E: causes yellow of skin/ brown pee (no treatment)