Antibiotics and infection controlEdexcel International A Level Biology: Mind map

Exam questions on Antibiotics and infection control

1. A hospital laboratory compares two antibiotics on separate cultures of the same bacterium. When antibiotic X is added, the number of living bacteria stops increasing but does not fall. When antibiotic Y is added, the number of living bacteria falls rapidly.
   Explain how a patient with a healthy immune system could still recover from an infection treated with antibiotic X.2 marks
2. A student spreads a culture of a harmless bacterium evenly over nutrient agar in a Petri dish. She places on the surface four paper discs, each 6 mm in diameter, soaked in antibiotic P, antibiotic Q, antibiotic R and sterile water. All antibiotic solutions have the same concentration. She tapes the lid on, inverts the dish and incubates it at 25 degrees Celsius for 48 hours. The clear zones around the discs measure 18 mm for P, 6 mm for Q, 24 mm for R and 6 mm for sterile water.
   Calculate the area of the clear zone around antibiotic R. Use the formula area = pi r squared, and give your answer in mm squared.2 marks
3. On a hospital ward, six patients developed infections with MRSA, a strain of Staphylococcus aureus that is resistant to methicillin. Investigators found the bacterium on the hands of some staff and on bed rails.
   Suggest three measures that could reduce the spread of MRSA on the ward, and explain how each would help.3 marks