Micro High Yield Final

What are the major discoveries and scientists you need to know?

• Robert Hooke — observed cork and used the term cell.

• Antonie van Leeuwenhoek — first to observe living microorganisms using microscopes.

• Louis Pasteur — supported germ theory, developed pasteurization, and disproved spontaneous generation.

• Robert Koch — developed Koch's postulates to connect a specific microorganism with a specific disease.

• Joseph Lister — introduced antiseptic practices into surgery.

• Edward Jenner — developed the first successful vaccination against smallpox.

Key idea:

Microbiology developed from the discovery that microorganisms exist → some cause disease → microorganisms can be controlled/prevented.

What are germ theory, spontaneous generation, and biogenesis?

• Germ theory: microorganisms can cause infectious disease.

• Spontaneous generation: old idea that living organisms could arise from nonliving matter.

• Biogenesis: living organisms come from preexisting living organisms.

Pasteur's experiments provided evidence against spontaneous generation and supported biogenesis.

What are the three domains of life?

1. Bacteria — prokaryotic cells.

2. Archaea — prokaryotic cells, but genetically/chemically distinct from bacteria.

3. Eukarya — organisms with eukaryotic cells, including fungi, protozoa, plants, and animals.

Viruses are not placed in the three domains because they are acellular.

What are the major types of chemical bonds and why do they matter?

• Ionic bond: electrons are transferred; produces charged ions.

• Covalent bond: electrons are shared.

• Hydrogen bond: weak attraction between partially charged molecules.

Hydrogen bonds are especially important for water, protein structure, and DNA base pairing.

What are the four major biological macromolecules?

Macromolecule	Main function
Carbohydrates	Quick energy + structural components
Lipids	Long-term energy, membranes
Proteins	Enzymes, structure, transport, defense
Nucleic acids	DNA/RNA; genetic information

Proteins are made from amino acids.
DNA/RNA are made from nucleotides.

Why is water so important to microorganisms?

Water is required for most cellular reactions. It acts as a solvent, participates in chemical reactions, transports substances, and helps regulate temperature.

Microorganisms also depend on osmotic balance. If water leaves a cell because of a hypertonic environment, the cell can shrink/plasmolyze.

What are the major microscopy concepts you need to know?

• Magnification = makes an object appear larger.

• Resolution = ability to distinguish two objects as separate.

• Contrast = difference between specimen and background.

Important microscopes:

• Bright-field: commonly used; specimen usually stained.

• Dark-field: bright specimen against dark background; useful for thin organisms.

• Phase-contrast: enhances differences in density; useful for living cells.

• Fluorescence: uses fluorescent dyes/antibodies.

• Electron microscopy: much higher resolution than light microscopy.

Remember:

• Magnification ≠ resolution.

• You can make something bigger without being able to see additional detail.

What is the purpose of staining and what are the major stains?

Staining increases contrast, making microorganisms easier to see and identify.

Simple stain: uses one dye to show shape, size, and arrangement.

Differential stains: distinguish different groups of organisms.

Gram Stain

Gram-positive:

• Thick peptidoglycan

• Retains crystal violet

• Appears purple

Gram-negative:

• Thin peptidoglycan

• Has an outer membrane

• Contains LPS

• Takes up counterstain

• Appears pink/red

Other important stains:

• Acid-fast stain → identifies organisms such as Mycobacterium.

• Endospore stain → identifies bacterial endospores.

• Capsule stain → demonstrates capsules.

What is the difference between prokaryotic and eukaryotic cells?

Prokaryotes:

• Bacteria/Archaea

• No nucleus

• No membrane-bound organelles

• Usually circular chromosome

• Smaller/simple structure

Eukaryotes:

• Fungi, protozoa, plants, animals

• Have a nucleus

• Have membrane-bound organelles

• Linear chromosomes

• Larger/more complex

Both have:
DNA + ribosomes + cytoplasm + plasma membrane.

What are the major bacterial structures and what does each do?

• Capsule: protects bacteria and helps attachment; can help evade phagocytosis.

• Cell wall: gives shape and prevents osmotic lysis.

• Plasma membrane: controls what enters/leaves the cell.

• Flagella: movement.

• Fimbriae: attachment to surfaces.

• Sex pilus: DNA transfer during conjugation.

• Ribosomes: protein synthesis.

• Nucleoid: bacterial chromosome.

• Plasmids: extra DNA carrying useful traits such as resistance genes.

• Endospores: highly resistant survival structures.

What is the major difference between Gram-positive and Gram-negative cell walls?

Gram-positive = thick peptidoglycan + teichoic acids.

Gram-negative = thin peptidoglycan + outer membrane containing LPS.

The Lipid A portion of LPS is endotoxin and can cause systemic effects such as fever, inflammation, and shock. 

What are viruses and what makes them different from cells?

Viruses are acellular obligate intracellular parasites.

That means:

• They are not cells.

• They cannot reproduce independently.

• They must enter a host cell.

• They use the host's genetic/metabolic machinery to produce new viruses.

A complete virus particle is called a virion. 

What are the major parts of a virus?

• Genome: DNA OR RNA.

• Capsid: protein coat surrounding genome.

• Capsomeres: protein subunits making up capsid.

• Envelope: lipid membrane present in some viruses.

• Spikes: surface proteins used for attachment to host cells.

Important:

Viruses have either DNA or RNA—not both as their genome.

What are the steps of viral replication?

Attachment → Penetration → Uncoating → Synthesis → Assembly → Release

• Attachment: virus binds host receptor.

• Penetration: virus/genome enters cell.

• Uncoating: viral genome is released.

• Synthesis: viral nucleic acids/proteins are produced.

• Assembly: new virions are constructed.

• Release: new viruses leave the cell.

What are the important viral life cycles and cytopathic effects?

Lytic cycle: virus rapidly replicates → host cell is damaged/lysed → viruses are released.

Lysogenic/latent infection: viral genetic material remains associated with the host and may become active later.

Cytopathic effects (CPEs) are visible changes viruses cause in infected cells.

Important CPEs:

• Cell lysis → cell bursts/dies.

• Syncytia → infected cells fuse together.

• Inclusion bodies → abnormal material accumulates.

• Transformation → cell changes that can contribute to cancer.

• Persistent infection → virus remains in the body.

Your class activity specifically identifies cell lysis as the fastest destructive CPE and notes that transformation can lead to cancer.

What are heterotrophs, autotrophs, phototrophs, and chemotrophs?

Heterotrophs: obtain carbon from organic compounds made by other organisms.

Autotrophs: use CO₂ as their carbon source.

Phototrophs: obtain energy from light.

Chemotrophs: obtain energy from chemical compounds.

These categories can be combined—for example, an organism can be a chemoheterotroph. 

What are diffusion, osmosis, active transport, phagocytosis, and pinocytosis?

• Diffusion: molecules move from high → low concentration; no ATP required.

• Osmosis: water moves across a selectively permeable membrane from lower solute concentration → higher solute concentration.

• Active transport: molecules move using membrane proteins and ATP.

• Phagocytosis: "cell eating"; engulfment of large particles/cells.

• Pinocytosis: "cell drinking"; uptake of liquids/dissolved substances.

What environmental conditions affect microbial growth?

The major factors are:

• Temperature

• Oxygen

• pH

• Osmotic pressure

• Pressure

Temperature groups:

• Psychrophiles: cold-loving.

• Psychrotrophs: can grow in cold environments, including refrigeration.

• Mesophiles: moderate temperatures; most human pathogens.

• Thermophiles: high temperatures.

pH groups:

• Acidophiles: acidic environments.

• Neutrophiles: near-neutral environments; most human pathogens.

• Alkaliphiles: alkaline environments

What are the oxygen categories?

Obligate aerobe: requires O₂.

Facultative anaerobe: grows with or without O₂ but prefers O₂.

Obligate anaerobe: cannot tolerate O₂.

Microaerophile: requires O₂ but at lower-than-atmospheric concentrations.

Aerotolerant anaerobe: does not use O₂ but can survive it.

Examples from your notes:

• M. tuberculosis → obligate aerobe.

• H. pylori → microaerophile.

• Staphylococcus → facultative anaerobe.

• Lactobacillus → aerotolerant anaerobe. 

What are the four phases of bacterial growth?

1. Lag: bacteria adapt to environment; little division.

2. Log/exponential: rapid cell division; population increases exponentially.

3. Stationary: nutrients decrease/waste increases; growth rate ≈ death rate.

4. Death: cells die faster than they reproduce.

⭐ Exam:

Antibiotics work particularly well against actively growing bacteria during log phase.

What are catalase and superoxide dismutase?

Oxygen metabolism can produce toxic reactive oxygen species.

Superoxide dismutase (SOD):
converts superoxide → hydrogen peroxide.

Catalase:
converts hydrogen peroxide → water + oxygen.

These enzymes help organisms tolerate oxygen. 

What are metabolism, catabolism, and anabolism?

Metabolism = all chemical reactions occurring inside a cell.

Catabolism = breaking down

• Complex → simple molecules.

• Releases energy.

• Produces ATP, electrons, and building blocks.

Anabolism = building up

• Simple → complex molecules.

• Requires energy.

• Builds proteins, DNA, cell walls, etc. 

What are enzymes, denaturation, oxidation, reduction, NAD⁺, and NADH?

• Enzymes are biological catalysts that lower activation energy, allowing reactions to happen faster.

• Denaturation occurs when environmental conditions disrupt an enzyme's shape, changing its active site so the substrate can no longer bind.

• Oxidation = loss of electrons.

• Reduction = gain of electrons.

• Remember:

• OIL RIG = Oxidation Is Loss, Reduction Is Gain.

• NAD⁺ = oxidized form.

• NADH = reduced form carrying electrons/hydrogen

What happens during aerobic respiration?

Overall:

Glucose + O₂ → CO₂ + H₂O + ATP

Major stages:

1. Glycolysis: glucose → 2 pyruvate; occurs in cytoplasm.

2. Acetyl-CoA formation: pyruvate → acetyl-CoA + CO₂ + NADH.

3. Krebs cycle: produces CO₂, ATP, NADH, FADH₂.

4. ETC: electrons from NADH/FADH₂ move through electron carriers.

5. Chemiosmosis: H⁺ gradient drives ATP synthase.

⭐ Most important:

O₂ is the final electron acceptor.

Your notes give a maximum of about 30–32 ATP per glucose for the pathway described. 

How is fermentation different from aerobic respiration?

Fermentation:

• Begins with glycolysis.

• Does not use the Krebs cycle.

• Does not use the ETC.

• Produces much less ATP.

• Allows glycolysis to continue when oxygen/respiration cannot supply the needed pathway.

Examples include:

• Lactic acid fermentation

• Alcoholic fermentation → ethanol + CO₂

How does DNA replication work and what do the major enzymes do?

DNA replication is semiconservative because each new DNA molecule contains one original strand and one newly synthesized strand.

Enzymes:

• Helicase: unzips DNA.

• Primase: creates RNA primers.

• DNA polymerase III: adds new DNA nucleotides.

• DNA polymerase I: removes/replaces RNA primers.

• Ligase: seals DNA fragments.

• Topoisomerase: relieves DNA supercoiling.

What are transcription and translation?

Transcription = DNA → RNA

DNA information is copied into mRNA.

Translation = mRNA → protein

The ribosome reads mRNA codons, while tRNA brings amino acids to build the protein.

Central dogma:

DNA → RNA → Protein

Exceptions include RNA viruses and retroviruses.

What are plasmids, operons, and the important bacterial gene-expression concepts?

• Plasmid: small circular DNA separate from the bacterial chromosome; can carry antibiotic resistance, virulence, or metabolic genes.

• Operon: group of genes controlled together and transcribed as one unit.

• Inducible operon: normally OFF → turned ON when needed.

• Repressible operon: normally ON → turned OFF when enough product exists.

• Cotranslational translation: in bacteria/Archaea, translation can begin while transcription is still occurring because there is no nucleus separating them.

What are transformation, transduction, and conjugation?

• Transformation: bacteria take up free DNA from the environment.

• Transduction: a bacteriophage transfers bacterial DNA from one bacterium to another.

• Conjugation: direct DNA transfer between bacteria, usually through an F pilus.

Why important?

• These are forms of horizontal gene transfer (HGT) and can rapidly spread traits such as antibiotic resistance. 

What mutation types and resistance concepts are high yield?

• Silent mutation: DNA changes but amino acid stays the same.

• Missense: changes an amino acid.

• Nonsense: creates a stop codon.

• Frameshift: insertion/deletion changes the reading frame.

UV radiation → thymine/pyrimidine dimers.

X-rays → chromosome/DNA damage.

Antibiotic resistance:

A random resistant mutation may already exist. Antibiotic kills susceptible bacteria → resistant bacteria survive → resistant population increases.

The antibiotic does not create the mutation; it selects for resistant bacteria.

What is the difference between sterilization, disinfection, antisepsis, and sanitation?

• Sterilization: destroys all microorganisms, including endospores.

• Disinfection: destroys/removes pathogens on nonliving surfaces.

• Antisepsis: destroys/removes pathogens on living tissue.

• Sanitation: reduces microbial contamination to safe levels.

⭐ Most resistant:

Bacterial endospores.

What are the major physical methods of microbial control?

• Autoclaving: steam + pressure + heat; 121°C, 15 psi, 15 min; sterilizes and kills endospores.

• Dry heat: requires higher temperature/longer exposure than moist heat.

• UV radiation: causes pyrimidine dimers in DNA.

• Ionizing radiation: X-rays/gamma rays → free radicals and DNA damage.

• Filtration: physically removes microbes from liquids/air; useful for heat-sensitive materials.

• Refrigeration: slows microbial growth but generally does not kill microbes.

• Desiccation: removes water.

• Lyophilization: freeze-drying for long-term preservation. 

What chemical controls should you know?

• Chlorine/bleach: denatures enzymes.

• Iodine: disrupts proteins; skin antiseptic.

• Hydrogen peroxide: produces free radicals.

• Aldehydes: cross-link proteins/DNA.

• Ethylene oxide: alkylates DNA/proteins; useful for heat-sensitive equipment.

• Chlorhexidine: damages membranes/proteins.

• Ethanol: damages membranes/dissolves lipids.

High salt/sugar creates a hypertonic environment → water leaves bacterial cells → plasmolysis. This preserves food but is not sterilization. 

What are selective toxicity, broad-spectrum/narrow-spectrum drugs, MIC, and Kirby-Bauer?

• Selective toxicity: drug harms the microorganism more than the host.

• Broad-spectrum: works against many types of bacteria.

• Narrow-spectrum: targets a smaller group.

• MIC (minimum inhibitory concentration): lowest concentration of an antimicrobial that prevents visible microbial growth.

• Kirby-Bauer test: antibiotic disks are placed on bacteria; the zone of inhibition shows how well the organism is inhibited.

How do major antimicrobial drugs work?

Know the general target:

• Penicillins/β-lactams: interfere with bacterial cell wall synthesis.

• Clavulanic acid: inhibits β-lactamase, protecting certain β-lactam antibiotics.

• Sulfonamides: interfere with folate synthesis.

• Fluoroquinolones: interfere with bacterial DNA replication.

• Polymyxins: damage bacterial membranes.

• Metronidazole: damages DNA in susceptible anaerobic organisms/protozoa.

• Acyclovir: antiviral used against herpesviruses; interferes with viral DNA replication.

• Quinine: antimalarial.

How does antibiotic resistance develop and what are persister cells, R factors, biofilms, and superinfection?

• Resistance: bacteria survive an antimicrobial because of genetic changes or acquired resistance genes.

• R factors: plasmids carrying antibiotic-resistance genes.

• HGT: allows resistance genes to spread between bacteria.

• Persister cells: metabolically inactive/tolerant cells that survive treatment without necessarily being genetically resistant.

• Biofilms: organized microbial communities attached to surfaces and surrounded by protective material; they are harder to eliminate.

• Superinfection: opportunistic organisms overgrow after normal microbiota are destroyed.

Examples:
Antibiotics → Lactobacillus killed → Candida overgrowth → yeast infection.

Or:

Broad-spectrum antibiotic → normal colon flora destroyed → C. difficile overgrowth → toxins → diarrhea/colitis.

What are resident microbiota, transient microbiota, true pathogens, and opportunistic pathogens?

• Resident microbiota: microorganisms that normally live on/in the body; usually harmless or beneficial.

• Transient microbiota: microorganisms temporarily present from the environment/contact.

• True pathogens: can cause disease in healthy individuals.

Opportunistic pathogens: normally don't cause disease but can when:

• They enter an abnormal body site, or

• Host defenses are weakened.

Normal microbiota protect us through microbial antagonism by occupying attachment sites, competing for nutrients, changing pH, and producing inhibitory substances.

What are the major steps a pathogen takes to cause disease?

1. Portal of entry → 2. Adhesion → 3. Survive host defenses → 4. Cause damage → 5. Exit host

Infectious dose (ID) = minimum number of organisms needed to establish infection.

A smaller infectious dose generally indicates greater virulence.

Adhesion = pathogen attaches firmly to host cells so it isn't removed and can colonize.

What are virulence factors, exoenzymes, exotoxins, and endotoxin?

Virulence factor: microbial structure/characteristic that helps the organism establish infection or cause damage.

Exoenzymes: secreted enzymes that break down tissues or barriers.

Examples:

• Mucinase → breaks down mucus.

• Hyaluronidase → breaks down material between cells.

• Coagulase → causes clotting.

Toxins:

• Neurotoxin → nervous system.

• Enterotoxin → intestines.

• Hemotoxin → red blood cells.

• Nephrotoxin → kidneys.

Endotoxin = LPS of Gram-negative bacteria, especially Lipid A. It can cause fever, inflammation, hemorrhage, diarrhea, shock.

What are signs, symptoms, syndrome, latency, sequelae, zoonosis, and HAIs?

• Sign: objective evidence observed/measured by others.

• Symptom: subjective experience reported by patient.

• Syndrome: combination of signs and symptoms.

• Latency: pathogen remains dormant/inactive and can reactivate later.

• Sequela: long-term/permanent damage after an infection.

Examples:

• Strep throat → rheumatic heart disease.

• Lyme disease → arthritis.

• Polio → paralysis.

• Zoonosis: disease naturally maintained in animals that can be transmitted to humans.

• HAI: healthcare-associated infection acquired during healthcare

What are the first and second lines of defense?

First line = prevent entry

• Skin

• Mucous membranes

• Cilia

• Stomach acid

• Tears

• Saliva

• Normal microbiota

Second line = attack after entry

• Phagocytosis

• Inflammation

• Fever

• Antimicrobial proteins

• Complement

• Interferons

• NK cells

PAMPs are microbial molecular "warning signs"; PRRs recognize them and trigger innate immune responses. 

What are PAMPs, PRRs, inflammation, fever, and antimicrobial peptides?

PAMPs: structures common to microbes that signal "foreign."

Examples:

• Peptidoglycan

• LPS

• Viral double-stranded RNA

• PRRs: host receptors that detect PAMPs.

• Inflammation: nonspecific response to tissue injury/infection characterized by redness, heat, swelling, and pain.

• Fever: pyrogens cause the hypothalamus to increase body temperature. Fever can inhibit some microbial growth and improve immune activity.

• Defensins: antimicrobial peptides that insert into bacterial membranes, form pores, and can cause lysis. 

What makes adaptive immunity different from innate immunity?

Adaptive immunity is:

Specific → targets a particular antigen.

Has memory → remembers previous exposure.

More powerful upon re-exposure → secondary response is faster and stronger.

The two major arms are:

Humoral immunity → B cells → antibodies

Cell-mediated immunity → T cells → cellular immune responses

What are IgM, IgG, IgA, IgE, and IgD?

IgM

First antibody produced during a primary response.

IgG

Most important long-term/secondary-response antibody; major antibody in the memory response.

IgA

Important in mucosal secretions such as saliva, tears, and breast milk.

IgE

Associated with allergic reactions and parasites.

IgD

Associated with B-cell function/receptor activity.

What happens during the primary vs. secondary immune response?

Primary response = first exposure.

• Slower.

• IgM appears first.

• IgG follows.

• Memory cells are generated.

Secondary response = later exposure to same antigen.

• Much faster.

• Much stronger.

• Primarily IgG.

• Higher antibody titer.

⭐ Vaccine connection:

Vaccines intentionally create a primary response and memory cells, so later exposure produces a rapid, powerful response

What are the important vaccine concepts?

Vaccination produces artificial active immunity.

Major vaccine types in your material:

• Live attenuated

• Killed/inactivated

• Subunit

• Genetically engineered

• Conjugate vaccines

Adjuvant: substance added to enhance the immune response; your slides identify alum as a common adjuvant.

Herd immunity: enough people are immune that a pathogen has difficulty spreading, helping protect vulnerable individuals.

Important: your class material specifically states there is no causal link between MMR vaccination and autism

What are hypersensitivity, autoimmunity, and immunodeficiency?

• Hypersensitivity: immune response is excessive or inappropriate and causes tissue damage.

• Autoimmunity: immune system attacks the body's own tissues.

• Immunodeficiency: immune system cannot adequately protect the body.

Big distinction:

• Hypersensitivity = too much/inappropriate response.

• Autoimmunity = response against self.

• Immunodeficiency = insufficient defense.

What are the major types of hypersensitivity?

• Type I: immediate allergic reaction involving IgE, mast cells, and histamine. Severe systemic reaction = anaphylaxis.

• Type II: antibodies attack specific cells/tissues.

• Type III: antigen-antibody complexes deposit in tissues and cause inflammation.

• Type IV: delayed, T-cell-mediated reaction.

High-yield:

• Type I = allergy/anaphylaxis.

• Type IV = delayed T-cell response.

What skin infections and clinical clues are high yield?

MRSA

• Methicillin-resistant Staphylococcus aureus.

• Can cause skin infections and serious systemic infections.

Necrotizing fasciitis

• Rapidly progressive infection that destroys fascia/soft tissue.

• Clinical clue:

  • Severe pain + swelling + rapidly progressing tissue destruction after a wound.

• Your PDF includes the nail-salon puncture case, where severe symptoms developed rapidly and emergency surgery was required.

Measles

• Koplik spots + fever + characteristic rash.

Chickenpox

• Varicella-zoster virus → vesicular rash.

Shingles

• Reactivation of latent varicella-zoster virus in sensory nerves → painful rash in a dermatome.

What are the major fungal/eye infections you should recognize?

Know the difference between:

• Dermatophytes: infect keratinized tissues such as skin, hair, nails.

• Candida: opportunistic yeast that can cause mucosal/skin infections.

• Conjunctivitis: inflammation/infection of conjunctiva; can be bacterial or viral.

What is the difference between meningitis and encephalitis?

• Meningitis = inflammation of the meninges surrounding the brain/spinal cord.

• Encephalitis = inflammation of brain tissue.

Meningitis:

• Bacterial → usually severe

• Viral → usually milder

• Fungal → often chronic

What are the major CNS diseases and their hallmark clues?

Neisseria meningitidis
→ Gram-negative diplococcus + capsule + college dorm outbreaks + petechial rash + possible DIC.

Poliovirus
→ attacks motor neurons → flaccid paralysis.

Botulism
→ blocks acetylcholine release → flaccid paralysis → "can't move."

Tetanus
→ blocks inhibitory neurotransmitters → spastic paralysis → "can't relax."

Rabies
→ animal bite exposure; once symptoms begin, disease is almost always fatal. Immediate post-exposure treatment with HRIG + vaccine is critical.

What are prions and why are they important?

Prions are infectious misfolded proteins.

They contain:
NO DNA and NO RNA.

They cause normal proteins to misfold, producing progressive brain degeneration and a spongiform/sponge-like brain.

Examples:

• Creutzfeldt-Jakob disease

• Variant CJD

• Mad cow disease

They are extremely resistant to normal sterilization methods.

What is the difference between viremia, bacteremia, septicemia, and septic shock?

• Viremia: viruses in the bloodstream.

• Bacteremia: bacteria in the bloodstream; may be temporary.

• Septicemia/sepsis: systemic response associated with infection, potentially involving microbial growth/toxins and widespread inflammation.

• Septic shock: severe sepsis causing profound hypotension and organ failure.

The cardiovascular system is normally sterile, so microbes entering blood can spread rapidly throughout the body. 

What are the high-yield cardiovascular diseases?

Endocarditis

Infection of the heart's inner lining/valves.

Classic clues:
Fever + heart murmur + damaged/prosthetic valve or risk factor such as dental procedure.

Janeway lesions = painless.

Osler nodes = painful.

Sepsis

Infection triggers massive inflammatory response → vasodilation + increased vascular permeability → low blood pressure → poor tissue perfusion → possible organ failure.

What is malaria and what is the life cycle?

Malaria is caused by Plasmodium.

Transmission:
Female Anopheles mosquito.

Major stages:

1. Mosquito injects sporozoites.

2. Parasites travel to the liver.

3. Multiply in liver cells.

4. Merozoites enter bloodstream.

5. Infect RBCs.

6. RBCs rupture → release parasites → repeat cycle.

7. Mosquito takes up parasites and sexual reproduction occurs in mosquito.

RBC destruction causes cyclic fever and anemia.

P. falciparum is the most severe/high-mortality species in your notes.

What respiratory diseases should you immediately associate with their organisms?

Disease	Organism	Hallmark
Strep throat	S. pyogenes	Sore throat
Scarlet fever	S. pyogenes + SPE toxin	Sandpaper rash/strawberry tongue
Diphtheria	C. diphtheriae	Gray pseudomembrane
Typical pneumonia	S. pneumoniae	Common bacterial pneumonia
Walking pneumonia	M. pneumoniae	Mild symptoms; no cell wall
TB	M. tuberculosis	Acid-fast; hemoptysis
Pertussis	B. pertussis	Whooping cough
PCP	Pneumocystis	Opportunistic pneumonia in AIDS

What are antigenic drift and antigenic shift?

• Antigenic drift = small genetic changes/mutations in viral antigens.

• Antigenic shift = major genetic change, especially through reassortment in influenza A.

⭐ Remember:

• Drift = small change.

• Shift = BIG change → pandemic potential.

Case:

Asian traveler + fever + dry cough + body aches + Hong Kong + live animal market → Influenza A, possible antigenic shift strain.

What are the major respiratory clinical cases?

• Infant + severe coughing fits + cyanosis + apnea → Pertussis.

• Acid-fast bacillus + hemoptysis → TB.

• No cell wall + mild pneumonia → Mycoplasma.

• AIDS/immunocompromised + opportunistic pneumonia → PCP.

• Gray pseudomembrane → Diphtheria.

What are the major GI diseases and their hallmark clues?

Helicobacter pylori

→ peptic ulcers.

Urease → urea → ammonia → neutralizes stomach acid.

Chronic infection increases risk of gastric cancer. 

Vibrio cholerae

→ cholera.

Cholera toxin → intestinal cells release huge amounts of water/electrolytes → massive watery/rice-water diarrhea.

STEC/E. coli O157:H7

→ bloody diarrhea + HUS.

Associated with undercooked ground beef.

Do NOT treat with antibiotics because increased Shiga toxin release can worsen HUS. 

Shigella

→ bloody diarrhea/dysentery + fever.

C. difficile

→ diarrhea after antibiotics.

S. aureus food poisoning

→ rapid vomiting 4–6 hours after food.

Botulism

→ descending/flaccid paralysis after contaminated/home-canned food.

Typhoid

→ high fever + rose spots.

Pinworm

→ severe nighttime anal itching in children.

Case 1 — 4-year-old with bloody diarrhea

Clues:

• Bloody diarrhea

• Fever/vomiting

• Ground beef exposure

• Dehydration

• Kidney damage

• Destroyed RBCs

Answer:
STEC E. coli O157:H7 → Hemolytic Uremic Syndrome (HUS).

Why HUS?

Shiga toxin damages blood vessels, especially affecting RBCs and kidneys.

⭐ Treatment point:

Do NOT give antibiotics because bacterial killing can increase Shiga toxin release and worsen HUS. 

Case 2 — Cyclospora outbreak

Clues:

• Large outbreak

• Fresh produce/lettuce

• Watery diarrhea

• Intestinal inflammation

• Malabsorption

Answer:
Cyclospora.

Key distinction:
Your notes emphasize that Cyclospora outbreaks are strongly associated with fresh produce, unlike many bacterial foodborne illnesses associated with meat/poultry.

What are the major UTI concepts?

The kidneys, ureters, bladder, and upper urethra are normally sterile because urine constantly flushes microorganisms away.

Cystitis = bladder infection.

Symptoms:

• Dysuria/burning

• Frequency

• Urgency

• Cloudy urine

• Possible blood

Pyelonephritis = kidney infection and is more serious.

E. coli causes about 80% of UTIs according to your course notes. Other organisms include S. saprophyticus and Enterococcus. 

What STIs and GU diseases should you know by hallmark finding?

Disease	Organism	Hallmark
Gonorrhea	N. gonorrhoeae	Purulent discharge + painful urination
Chlamydia	C. trachomatis	Often asymptomatic; PID risk
Trichomoniasis	T. vaginalis	Green/frothy discharge
Candidiasis	C. albicans	White/curd-like discharge
Syphilis	T. pallidum	Painless chancre
Genital herpes	HSV-2	Painful blisters
HPV	Human papillomavirus	Genital warts + cervical cancer
GBS	Group B Strep	Neonatal infection risk

What should you know about HPV, GBS, and reactive arthritis?

HPV

Some HPV strains cause genital warts; high-risk strains can cause cervical cancer and other cancers.

High-risk types listed in your notes include:
HPV-16, 18, 31, 33, 35.

Prevention includes Gardasil vaccination and screening such as Pap testing. 

Group B Strep

Can colonize women without symptoms but can be transmitted to newborns during birth and cause serious neonatal disease.

Reactive arthritis

Can occur 1–4 weeks after infection.

Classic phrase:

"Can't see, can't pee, can't climb a tree."

• Can't see → conjunctivitis

• Can't pee → urethritis

• Can't climb a tree → arthritis

Triggers listed in your notes include Chlamydia, Salmonella, and Campylobacter.