Microbial Contamination in Multi-Dose Ophthalmic Solutions: A Study on Patient-Used Eye Drops

AbstractThis study investigates the microbial contamination of patient-used ophthalmic solutions and assesses potential contamination sources. Fifty-five multi-dose ophthalmic solution samples were collected from patients after treatment. Sterility testing was performed using the direct inoculation method in accordance with the European Pharmacopoeia (Ph. Eur. 11.0). Contaminant microorganisms were identified at the species level using Matrix-Assisted Laser Desorption/Ionization–Time of Flight Mass Spectrometry (MALDI-TOF MS). Among the tested samples, only one sample (1.8%) exhibited microbial contamination. Two distinct bacterial species were identified: Micrococcus luteus and Dermacoccus nishinomiyaensis. The contamination was detected in an expired sample, highlighting the potential risk associated with using ophthalmic solutions beyond their shelf life. Although the contamination rate was low, this study underscores the importance of maintaining strict hygiene practices while using ophthalmic drugs. Educating patients on proper handling, storage, and adherence to expiration dates is crucial to minimizing contamination risks. Further studies with larger sample sizes and preservative-free formulations are recommended to comprehensively assess microbial contamination patterns in ophthalmic solutions. These findings provide valuable insights into contamination risks in ophthalmic solutions, emphasizing the necessity of stringent quality control and patient education to minimize microbial growth. Keywords: Microbial contamination, Ophthalmic solutions, Sterility testing, Microbiological quality control, Antimicrobial preservatives