Biology Exam Preparation Notes

Antibiotic Use and Selection

• Need to choose the best antibiotic based on infection type.
• Important to consider side effects, e.g., quinolones leading to tendon rupture.

Tuberculosis Treatment

• Must know the last drug used for tuberculosis.
• Consider patient's general status and potential disability.

Microbiome Considerations

• Microbiome can be affected by various conditions such as:
  • Exposure to children.
  • The relationship between normal microbiota and the host termed microbial antagonism.
• Microbial Antagonism:
  • Competition among microbes for nutrients.
  • Microbes may release toxins that kill competitors or modify local environments, e.g., altering pH and oxygen levels, affecting microbial survival.

Symbiotic Relationships

• Symbiosis Types:
  • Commensalism: One organism benefits while the other remains unaffected (e.g., microbes consuming dead skin).
  • Mutualism: Both organisms benefit (e.g., gut microbiome).
  • Parasitism: One organism benefits at the expense of the other (important in infectious diseases).

Koch's Postulates for Disease Identification

1. The same pathogen must be present in every case of the disease.
2. The pathogen must be isolated from the diseased host and grown in culture.
3. The pathogen must cause the same disease when introduced into a healthy host.
4. The pathogen must be re-isolated from the inoculated host and identified.

Disease Signs and Symptoms

• Subjective: Patient-reported symptoms (e.g., sore throat).
• Objective: Measurable data (e.g., blood pressure, temperature).
• Syndrome: A group of signs and symptoms that occur together (e.g., Pain during urination as reported by a patient).

Classification of Diseases

• Classifications based on behavior include:
  • Communicable: Spreadable from one host to another.
  • Contagious: Easily spreadable.
• Epidemiology: The study of disease occurrences and transmission.
  • Incidence: New cases in a period.
  • Prevalence: Total cases at a given time, including both new and existing cases.

Understanding Incidence and Prevalence

• Incidence: New water added to a bath (new cases).
• Prevalence: Old and new water in the bath (total cases).
• Strategies to decrease incidence include vaccines and public health policies.

Immunity and Disease Spread

• Herd Immunity: When a certain proportion of a population is vaccinated, aiding in the protection of unvaccinated individuals.
• Vaccination can provide long-lasting immunity and control disease spread.

Stages of Infection Development

1. Reservoir: Source of a pathogen.
2. Transmission: Means by which the pathogen is transferred to a host.
3. Invasion: Pathogen enters and causes disease in the host.

Transmission Types

• Direct Contact: Touching, kissing, or sexual intercourse.
• Indirect Contact: Spreading via inanimate objects (fomites) like utensils and medical equipment.
• Airborne: Pathogens spread via aerosols over distances greater than one meter.
• Waterborne & Foodborne: Involvement of contaminated supplies leading to diseases (e.g. cholera).

Vector Transmission

• Vectors: Arthropods like ticks or mosquitoes that transmit diseases.
  • Can use:
  • Mechanical Transmission: Pathogen carried on body parts.
  • Biological Transmission: Pathogen injected through bites or stings.

Nosocomial Infections

• Caused mainly due to healthcare practices.
• Preventative measures include:
  • Strict hand hygiene by healthcare workers.
  • Disinfection of medical equipment.
  • Use of personal protective equipment (PPE).
  • Judicious use of antibiotics and aseptic techniques during procedures.