Health, disease and the development of medicines study guide

Immunisation, often referred to as vaccination, is a process that protects an individual from infectious diseases by stimulating their immune system to produce antibodies. This is typically achieved by administering a vaccine, which contains weakened or inactivated forms of pathogens, or parts of them like proteins or toxins. The primary benefit is reduced risk of severe illness or death for the immunised individual. On a broader scale, immunisation can lead to 'herd immunity.' This occurs when a high enough percentage of a population is immune to a disease, making its spread unlikely, thereby protecting those who cannot be immunised (e.g., infants, immunocompromised individuals). However, immunisation has limitations, including potential side effects, the need for ongoing vaccine development due to pathogen mutation, and the fact that vaccines are not 100% effective for everyone.

When investigating how antiseptics, antibiotics, or plant extracts affect microbial cultures, use standard aseptic techniques (disinfecting work areas, wearing gloves and goggles, using sterilised tools) and only permitted, non-pathogenic bacterial species. The independent variable is the type or concentration of antimicrobial agent, and the dependent variable is the zone of inhibition (clear area around the disc) on an agar plate. Control all possible variables, such as the same bacterial strain, agar depth and composition, incubation time, and disc size and placement. Carefully inoculate plates, add antimicrobial discs and a control, seal plates with tape, and label clearly. Incubate plates upside down at or below 25°C for safety. After incubation, do not open the plate – measure the inhibition zone diameter through the closed lid using a ruler. For graphical presentation: display antimicrobial type or concentration on the x-axis and mean zone diameter on the y-axis as a bar graph or line graph. Evaluate the reliability by repeating the experiment, calculating averages, and comparing data; assess uncertainty by comparing the ruler precision (for example, ±1 mm) to the measured zone, then calculate percentage error as (uncertainty/mean) × 100%. Dispose of all cultures and materials by sterilisation (e.g., autoclave) under supervision. Never incubate plates above 25°C or open plates after incubation in schools.