Could a Preservative Have Prevented the Extremely-Drug Resistant Pseudomonas aeruginosa Artificial Tears Associated Eye Infection Outbreak of 2023?

Purpose: The 2023 outbreak of extensively drug resistant (XDR) Pseudomonas aeruginosa (PA) eye infections was linked to the use of non-preserved, multi-use artificial tears purchased online. The lack of preservatives has been attributed to be the predominant factor in the outbreak. This led us to the current study for which the goal was to determine whether common ophthalmic preservatives could eliminate the outbreak XDRPA and other PA keratitis isolates.

Materials and methods: Time-kill studies were performed in Mueller-Hinton broth (MHB) and phosphate buffered saine (PBS) on 3 PA strains including the XDRPA outbreak strain. Preservatives assessed were benzalkonium chloride (BAK) 0.04%, 0.01%, and 0.004%, Polyquaterium-1 (Polyquad) (PQ) 0.001%, Sodium Perborate (SP) 0.1%, and EDTA 0.1%. In addition, time-kill assays were performed using preserved and a non-preserved commercially-available artificial tears.

Results: BAK 0.04% and 0.01%, and PQ eliminated all PA isolates in both media after 4 h. BAK 0.004% and SP eliminated all PA strains in PBS at 1 h but did not produce bactericidal 99.9% decreases in MHB over 24 h. EDTA did not produce a bactericidal effect in either media. Artificial tears containing sorbic acid 0.25% and edetate disodium 0.1%, PQ, SP, and PURITE eliminated the PA strains within 24 h.

Conclusions: Several common preservatives were effective in eliminating PA strains including the outbreak strain CDC1270. Preservative efficacy was delayed or inhibited in rich media (MHB) compared to PBS. These results suggest that the 2023 outbreak could have been prevented by using a common preservative in the artificial tears.