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Diseases and Immunity: Question 1

Syllabus 10.1

Multiple choice Core 1 mark

A gardener is tidying a flower bed using a pair of secateurs (pruning shears). Earlier that day, a neighbour used the same secateurs to trim a rose bush, without realising that a small, infected cut on his hand had left bacteria on the blades. The gardener does not clean the secateurs before using them, and a few days later she develops a similar bacterial skin infection at a small cut on her own hand.

Which statement correctly classifies how the bacterium was transmitted to the gardener, and gives the correct reason?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Step 1: Recall the difference between direct and indirect transmission

A transmissible disease is one in which a pathogen can be passed from one host to another. This can happen:

  • directly, through contact between hosts, including through blood and other body fluids, or
  • indirectly, by way of something in between the two hosts, such as a contaminated surface, food, an animal, or air.

Step 2: Apply this to the gardening scenario

The gardener never had any contact with the neighbour himself. Instead, the bacteria from the neighbour’s infected cut were left on the blades of the secateurs, an object that the gardener then used without cleaning. The bacteria travelled from the neighbour to the gardener by way of this contaminated tool, not through contact between the two people.

This matches the definition of indirect transmission, transmission by way of a contaminated surface or object.

Step 3: Rule out the other options

  • A: describes direct transmission, but there was no contact between the neighbour and the gardener; the bacteria travelled via the secateurs.
  • B: the two infections being caused by the same bacterium tells us nothing about how it travelled between the two people, so it cannot be used to justify “direct” transmission.
  • D: nothing in the scenario suggests the bacteria travelled through the air, they were carried on a contaminated surface (the secateurs’ blades).

Final answer

  • The bacterium was transmitted indirectly, by way of the contaminated secateurs, option C.