The liquid form of sodium fluorescein is very susceptible to contamination by which organism?

• A. Pseudomonas aeruginosa
• B. Staphylococcus aureus
• C. Streptococcus pneumoniae
• D. Escherichia coli

Answer: (A)

Sodium fluorescein in liquid form is especially vulnerable to contamination by organisms that thrive in moist, aqueous environments and are common in ophthalmic settings. Pseudomonas aeruginosa fits this pattern well: it readily grows in sterile eye solutions, including fluorescein, and is known for contaminating ophthalmic drops and contact lens solutions. It can survive in the bottle tip and form biofilms, making contamination difficult to prevent and preventable through proper sterile technique and handling. This is why Pseudomonas aeruginosa is the most likely contaminant for liquid fluorescein.

Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli can contaminate various things, but they are not as characteristically associated with contaminating ophthalmic liquid preparations as Pseudomonas in typical eye-care practice.