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Question 19M.3.SL.TZ1.d

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.3.SL.TZ1.d
Level SL Paper 3 Time zone TZ1
Command term Outline Question number d Adapted from N/A
d.
[Maximum mark: 1]
19M.3.SL.TZ1.d

Hexochlorophene (HCP) and ortho-phenylphenol (OPP) are two ingredients of handwashing formulations. The antiseptic effectiveness of the two agents was tested by soaking discs in the agents and applying them to plates inoculated with Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The resulting zones of inhibition are depicted.

[Source: © International Baccalaureate Organization 2019]

P. aeruginosa is a concern in hospitals because it tends to form biofilms. Outline one reason for biofilms being particularly difficult to eradicate.

[1]

Markscheme

microorganisms growing in a biofilm are resistant to antimicrobial agents ✔

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