Question

A person with prolonged use of contact lenses presented with irritation of the left eye. After examination, a diagnosis of keratitis was made and corneal scrapings revealed growth of Pseudomonas aeruginosa. The bacteria were observed to be multidrug resistant. Which of the following best explains the mechanism of antimicrobial resistance in these isolated Pseudomonas aeruginosa strains?

• A. Ability to transfer resistance genes from adjacent commensal flora
• B. Improper contact lens hygiene
• C. Frequent and injudicious use of topical antibiotics
• D. Ability of Pseudomonas to produce biofilms

Hint:

Think about the slimy matrix this organism builds on plastic lens surfaces.

Answer 1

The Correct Option is D

Step 1: The question asks for the MECHANISM of multidrug resistance in Pseudomonas aeruginosa associated with contact lens keratitis, not the risk factor for getting infected.
Step 2: Pseudomonas aeruginosa readily forms biofilms, a matrix of secreted polysaccharide (glycocalyx) in which the bacteria embed themselves, including on the surface of soft contact lenses and the cornea.
Step 3: Within a biofilm, antibiotics penetrate poorly, the bacteria grow slowly, and protected sub-populations survive. This makes the organism phenotypically resistant to many drugs at once, explaining the multidrug-resistant behaviour in this clinical setting.
Step 4: Option B (poor lens hygiene) and Option C (overuse of topical antibiotics) are risk factors or selection pressures, not the intrinsic mechanism by which this strain resists multiple drugs. Option A (gene transfer from commensals) is a general resistance route but is not the characteristic, lens-associated mechanism for Pseudomonas keratitis.
Step 5: The biofilm explains why the contact-lens-related Pseudomonas is hard to eradicate and resists several antibiotics simultaneously.
Hence the answer is Option D (Ability of Pseudomonas to produce biofilms).