hsci 212 midterm

Week 1 Concepts

• Agent, host, and environment need defining
• Describe the causal model in disease transmission
• Review descriptive epidemiology as applied to communicable diseases
• Review analytic epidemiology studies as applied to communicable diseases
• Describe differences between case-control and cohort studies
• Explain the importance of randomization in randomized controlled trials
• Understand and calculate odds ratio as a measure of association

Definitions

• A disease is a pathological condition of body parts or tissues characterized by a group of symptoms
• An infectious disease is caused by an infection agent such as bacteria, virus, or fungus, that can be passed on to others
• Epidemiology includes the Study of disease and other health related events in the population
  • Descriptive epidemiology examines the distribution of disease and observes the features of distribution
  • Analytic epidemiology tests a hypothesis about the cause of the disease by studying how exposures relate to the disease
• A communicable disease is an illness caused by infectious agents, which can be transmitted directly/indirectly
• All diseases have a host, agent and environment
  • The host is the individual who has the disease
  • The agent is the factor whose presence or absence can cause disease
  • Environment includes all external conditions and influences effecting life

Study Designs

• Cross-sectional study: at a point in time, the exposure and the disease status are collected at the same time
  • Research of stress levels in college students in various years of study, is an example of cross-sectional study
• Case-control study may collect retrospective data
  • Diseased and non-diseased study, and Dr might study coke intake associated with Colon Cancer
• Cohort studies follow subjects over time (prospectively & retrospectively)
  • Determine disease status
  • Ex: female nurses who smoke, vs those who don't
• Clinical trial study: subjects over time prospectively
  • Assign an exposure, over time to determine outcome
  • A new test or treatment is given, and effects on patients is evaluated

Prospective vs Retrospective

• Prospectively - individuals are followed over time and data about them is collected as their characteristics or circumstances change
• Retrospectively – Individuals are sampled and information is collected about their past by interviews or questions

General role of the Casula Model in Disease Transmission

• Understanding Relationships: It establishes cause-and-effect relationships between variables
• Prediction and Forecasting: By quantifying relationships, causal models can predict future outbreaks, identify high-risk populations, and estimate the potential impact of interventions
• Guiding Interventions: The model can identify leverage points for controlling or preventing disease
• Supporting Decision-Making: Causal models provide evidence-based insights for public health planning, resource allocation, and policy development
• Incorporating Feedback Loops: These models often account for dynamic feedback such as a decrease in susceptible individuals due to immunity reduces the transmission potential over time
  • In Covid, factors include: viral load, mask-wearing behavior, all interacting to determine the rate of disease spread

Descriptive vs Analytical Epidemiology

• Descriptive epidemiology examines the distribution of disease
  • Examines patterns related to person, place, and time
  • Focuses on understanding how infections spread, providing possibility for further analysis/intervention planning
• Analytical epidemiology uses a hypothesis to test the cause of disease
  • Studies how exposures relate to the disease
  • Determines factors that influence the occurrence, spread, and control of diseases

Case-Control vs Cohort studies

• A case-control study studies subjects at a certain point in time, and may also collect retrospective data.
  • Compares a group of healthy subjects to a group of diseased subjects to find out what caused the disease
• Cohort studies follow the subjects over a period
  • Collect prospective data and retrospective if needed
  • Compares Exposed vs non-exposed subjects for a particular outcome

Randomized Controlled Trials

• Randomization = baseline comparability between groups on factors related to outcome
• Allows researchers to evaluate safety/efficacy in a controlled manner

Odds Ratio

• Odds ratio expresses probability.
  • That is the probability of an event/ the probability of the event not happening
  • Can determine risk factor

Relative Risk

• Relative Risk (RR) includes proportions of people with the disease among the exposed/unexposed
• RR formula is: [a/(a+b)] / [c/(c+b)]

Week 2 Info

• Need to Name/describe general features of different types of disease-causing microorganisms

Microscopic Details

• Bacteria - single celled microoragnisims
  • Approximately 0.001 micor meters
  • Prokaryotes
  • FOOD POISINING is an Example
• Viruses - Roughly ~0.0001-0.00001
  • Exhibit many shapes depending on host cells
  • Rely on host cells for survival/replication
  • MYRAID is an Example
• Fungi – ranges from few micrometers to a few centimeters
  • Different shapes (single celled yeasts, multicellular molds)
  • Eukaryotic, or heterotropic
  • Cause a wide range of diseases like yeast infection/jock itch
• Parasites - have varying sizes

Bacteria

• Exhibits different shapes
  • (unicellular protozoa, multicellular helminths) -Eukaryotic
  • Relies on host for survival -Complex lifestyles
  • Causes wide range of diseases like Malaria & tapeworm

Microbiology

• Microbiology has two groups i.e. microscopic & macroscopic.
  • Micro organisms, such as Bacteria, Yeast, Ciruses, and Protozoans
  • Macro organisms, as Worms and Mold

Historical contributions - Semmelweis, Lister and Koch

• Lister (British surgeon)
  • Theorized Sepsis came from a pollen-like dust
  • Use of disinfection greatly improved survival after surgeries
  • Decreased post-operative infection
• Semmelweis: puerperal or childbed fever caused by an infection.
  • Introduced into the birth canal from outside prevented by chlorinous disinfection of the hands
• Koch: Experiment with bacterium, Bacillus anthracis

Koch's Postulates

• Used to explain how Koch's postulates can apply on a molecular scale
  • With this info, Kick's postulates was developed
  • Postulates include:
    • Agent is present in every disease case
    • Agent is isolated & grown in "pure" culture
    • Cultured agent causes disease when inoculated into a healthy host
    • Same agent must be reisolated from the diseased experimental host

Bacteria Naming

• Bacterial Naming - latin or greeke origin
  • Genus name ex: Escherichia
  • Species name: Coli
  • Example = E. coli

Bacterial Cell Walls

• Peptidoglycan is uniqe component of bacterial cell wall
  • Made of proteins (Peptido)/sugars (glyco)
  • Often targeted by antibiotics
• Bacteria with thick peptidoglycan walls stain purple = gram Positive
• Bacteria with outer membrane stain pink = gram Negative

Gene Transfer

• Vertical = generation to generation
  • Asexual reproduction i.e. less genetic diversity
• Horizontal = transfer of genetic material from one organism to another in the SAME generation
  • For example, transferring plasmids
  • KEY mechanism behind antibiotic resistance

Bacterial Shapes

• Coccus = circles
• Bacillus = pill shape
• Vibrio = arc
• Coccobacillus = oval
• Spirillum = spiral
• Spirochete more spiral

Microbes

• Organisms included in microbes
• Known as microorganisms and some of their key differentiating characteristics
• Bacteria, Viruses, Fungi, Protozoa

Microbial Definitions

• Infectious disease – damages a host cell, by growing microbes
• Pathogen – a microbe that can cause an infectious disease
  • Example: bacteria, fungi, viruses, or protozoa
• Parasites include a protozoa, or worm
• Virulence - how successful a microorganism is at infecting the host, and causing disease

Factors that affect host-pathogen interaction

• Host immune response
• Pathogen virulence factors
• Environmental factors

Virulence Factors

• What is the role of virulence factors in disease:
  • Adhesion molecules – how well the microorganisim can attach to the host cell
  • Endotoxins including bacterial toxins that contribute to the virulance of gram-negative bacteria
  • Exotoxins including agents acting as super antigens that causes tissue damage
    • Toxic shock is an example

Endospore formation

• Endospore formation is resistant to heat and chemicals
• Key in transmitting infectious disease, with a tough, non-reproductive structure

Biofilms

• Biofilms are a structure made of organisms, and allows for bacterial withsanding environmental stress
  • Formed on tissues: wounds, airways, or on foreign bodies: prosthetic joints
  • Causes infection

Pathogen

• These are the steps that are needed for a pathogen to cause and infectious disease
  • Maintain a reservoir
  • Transport to, then enter the host
  • Invade host cells
  • Evade host defense
  • Multiply
  • Damage host
  • Leave the host and return to a a new host

Gram +/-

• There are differences between gram negative and positive bacteria:
  • Positive: has a thick peptidoglycan layer, no outer membrane, purple, and more susceptible to antibiotics
    • Ex: Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis
  • Negative: has a thin peptidoglycan layer, has an outer membrane, pink/red gram stain, and more resistant to antibiotics
    • Ex: Escherichia coli, Salmonella typhi

Week 3 Info

Gram Stains

Understand what a gram stain is, and how it can differentiate between gram positive & gram-negative organisms

• A gram stain test differentiates between gram negative/positive organisms. A iodine die is added to the plate that containing the organism
  • If the organism turns purple, it has the thick outer layer of proteins
    • Gram-Positive
  • If it turns pink/red, the organism contains an outer membrane, and thin peptidoglycan layer
    • Gram-Negative

Microorganisim Modalities

• Understand different modalities that identify microorganisms. The modalities include:
  • MALDI-TOF includes pathogen identification and analyzing protein
    • Exposed to a laser, which causes the proteins to ionize
    • Ions are measured by their mass-to-charge ratio which generates a mass, unique to that organism
  • PCR identifies pathogen detection,amplifies DNA and detects the organisim
    • Highly-sensitive/specific, Fast
  • Culture/biochemical: Slow, Labor-Intense Routine
    • Growing/Observing
• DNA Sequencing identifies accurate ginetic identification, accurate but time-consuming
• Immunological identifies antigen-antibody reactions, antibody detection and pathogen detection. - Quick but sometimes less specific

Antibiotic Susceptibility

• Understand 3 different testing methods for antibiotic (disk diffusion, etest, MIC).
  • Disk diffusion: uses antibiotic impregnated paper disks placed on an agar plate with the test bacteria, measures spread
  • Etest: uses antibiotic impregnated strip w/gradient of antibiotic concentration
    • Place strip on inoculated agar plate
    • Antibiotic diffuses radially i.e. a concentration gradient
  • MIC or Minimum inhibitory concentration:
    • Lowest concentration of an antibiotic that inhibits bacterial growth

Selective Reporting

• Concept including antibiotics & reasons why used
  • Only certain antibiotic results reported to healthcare providers/doctors
  • Others aren't, based on their clinical relevance/treatment guidelines

Bacteria Growth Curve

• Lag phase - No cell division/growth
• Exponential phase – Shows rapid growth & constant bacteria division
• Stationary phase – Growth equal death = stable population size
• Death phase Decline and cell death exceeds new cell formation & overall loss

Bacterial Growth Control

• Methods to control bacterial growth prior to antibiotics, these include:
  • Heat: pasteurization
  • Refrigeration
  • Alters Acidity
  • Desiccation that is adding sugar to draw h2o out

Antibiotic Toxcity

• Understand selective toxicity and how antibiotics leverage unique differences of prokaryotic cells
  • Antibiotics aim for selective toxicity, that targets microbes while causing minimal harm.
  • In Prokaryotic and bacteria cells there are bacterial walls
• Bacteria have 70s ribosmes, different membranes and metabolic pathways.

Bactericidal & Bacteristatic Antibiotics

• Bactericidal antibiotic directly. Effective on immunocompromised patients, for example Penicillins
• Bacteriostatic antibiotics hinder bacterial growth, therefore it relies on immune system
  • Tetracyclines are an example

Antibiotic Spectrum

• There are both Broad vs narrow spectrums, each with benefits
• Broad spectrum Targets wide variety of bacterial pathogens when empiric therapy is needed (unknowing)
• Narrow spectrum targets one bacterial pathogen needed where there is less effect on Microbiome

Beta-Lactams

• Beta-lactame antibiotic can have hydrolysis in the beta-lactame ring.
• This is because of a Beta-lactamases which stops theirability to bind to the lenacillin binding
• In turn proteins makes the drug not useful

Drug Resistance Concepts

• Modification of target site and enzyme inactivation/drug resistance
• Microbes are constatly changing/evolving to better survive -Resistance comes from: - Selected random mutations passing through generations - Horizontal gene transfers

Antibiotics Reduction

• To reduce what way: - Reduce over-prescription of unnecessary antibiotics - Reduce antibiotics in the farming industry - Improve infection prevention & control

Week 4 & Virology & HIV

Virus Characteristics

• Requires the host cell genomes to reproduce-
• Infections, ACELLUCAR not composed of cells, cant reproduce independently - pathogens
  • DNA or RNA genome, but not both

Virion Genetic Components-

• Viron is a fully formed virus particle outside of the host cell.
• The core containing genetic info via RNA or DNA
• Protein Shell
• Envelope Lipid

Virus Lifecycle

• Attachment (binds to host cell uisng receptor molecules)
• Entry: -The virus or its genetic materials enter the host
  • Genome replication & gene expresission
    • Viral genome copied & genes exprssed to mass
• Release completes viral particles exit cell & can Infect more -

Enveloped and Naked Virus

• Enveloped: Layer the host ells membranes due replication
• Better, is a for invasion with less effects
  • Ex:Influenza
• Naked (no lipid) and more resistants
• Can resist drying the since lacking a fragile envelopes-
  • Ex:Morovirus

Viral Host Range-

• How determine is Specific determines is determined by the shape of the receptors.-
• The host cell Surface Range basis determines amount different-
• Is species organism the virus in the shape of the protein infect

RNA Replication-

• Positive single stranded RNA ssRNA: act as ssRNA is translated by host ribosomes -
• Reproduction occurs entirety entireytoplasm the genome is use immidatly use
• Single stranded-ssRna Cannot by inititiate Replication must needs polymerase in virion.

Persistant Virus-

• Latent: the chicken pocks (dormant cell)
• Chronic: Heps B+C through invading

Diagnosing Viral Infections-

• Electron misroscopy
• EnZymes
  • Cyopathic= Look abnormalitys Nucle acid amplification test -

Antigenetic Changes-

Drift: Spike Protein, Flu seasonal -

• Shirt: two different species

HIV and AIDS-

• HIV/ AIDS remain global health issue millions affected.
• Primarly transmission occurs through sexual contacts, or by sharing

HIV Life Cycle

• Fusion Capsid, Binds receptors Transcript, Integration, replication, Assembly binding -

Treatment Challenges

• Integration causes more High Mutation rate (replication)
  • Extended rate
    • Intergratoin

Antiretroviral Action-

Ingratase =Prevents -

HIV-1 cell-

Hosts =immune Agent (Human Imunno diffcency-vrus/ Enviormental-

Hiv Defintions

• Servodiscrond = the relationship is servonegative-
• Servocherssion= body is ditecting = after infection -immunne
• Oppotunistics,
  • 0ccur when cell are severlty weakened

Goals for HIV

• TasP treatement
• PREP/ pre expouser
• POP- Anti Therapy -

Reverse Roles

Retrovirils Protein Integrase and pretense and building build

Triple therapy-

Resistance = can improvce treat oppuortunic Infctions- Can cause reporduce and growth

Virlant Therapy and Positives/

• HATT therapy
• AIDs (Immune and transment

Week 5 -Fungal charateristics

-Is the host cells in the

• Eukaryotic- hard to treat
• chitin synthesis
• ergosoft -
• single/muldicellaur dimorphic
• Mycobioume = forms and fungal orgasim

Diagnsing Fungal

• Fungi has is the lungs microscope

Fungal Treatment

Binds the orgo - die cell

• inhibits the Ergosoal and celled inhibiton Stops orgao -