# Evaluating and Managing the Microbial Contamination of Eye Drops: A Two-Phase Hospital-Based Study
## 4 Discussion  
A two-phase study was conducted at the Pharmacy Unit--UPSO2, France. The first phase examined microbial contamination after the use of eye drops compounded by UPSO2, followed by a second phase that evaluated the effectiveness of eye drops incorporating Pylote antimicrobial technology in preventing the contamination of the dropper tip and cap and assessed the practical integration of the innovative packaging into the eye drop compounding process. In the initial phase, 33% of the tested eye drops used during hospitalization or returned by patients were contaminated by commensal and environmental bacteria and fungi. Those utilized by patients were contaminated (>91%) and exhibited higher microbial loads than the ones collected from the hospital. Consistent with our findings, two studies showed that preservative-free eye drops prepared in the hospital in multidose containers collected from patients had a higher microbial load than those used by healthcare providers [(41; 42)]. The results in this study align with the literature that evaluated preservative-free eye drops used in different settings and showed that microbial contamination varied between 2.3% and 73% [(8)]. Notably, the microbial contamination of preservative-free multidose eye drops prepared in the hospitals ranged between 8.4% and 28.9% [(41; 42; 43; 44)]. The microbial contamination of single- and multi-user eye drops is an established risk of infection, documented at a variable rate [(45; 14; 18; 46)] and in different settings, including hospitals, clinics, and homes, [(47; 48; 49; 13; 9; 14; 25; 45; 46; 9)] whether preserved or preservative-free [(47; 48; 49; 13; 9; 14; 28; 49; 50; 51; 52; 53; 54)]. A thirty-year literature review examined the microbial contamination rate of in-use eye drops and found multiple inconsistencies in the literature related to the study design and numerous other contributory factors [(8)]. The disparity in the reported rate of microbial contamination across different studies may be due to the sampling method, swabbed eye drop sites, the methodology of specimen collection and the transfer of tested samples, differences in the culture technique and media, the testing conditions, and the conducted microbiological assays [(8)]. In the present study, the microbial load of eye drops collected from the hospital was 8%, compared with 92% in those returned by patients. The hospi \begin{table} -  
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Table 1: Microbial loads on Activated RispharmTM packaging and standard packaging after 24 h of contact (mean \(\pm\) standard deviation). tal's strict hygiene protocols, the handling of the drug by nurses, and the usually short duration of use, predominantly in the operating room, may have contributed to the limited prevalence of microbial contamination in the hospital setting [14; 44; 45]. Other potential factors are associated with the type of eye drops collected from in-patients, predominantly comprising antibiotic formulations (90%). While these antimicrobial agents may effectively inhibit the growth of some microorganisms within the eye drop solution, their protective action does not necessarily extend to the external surfaces of the dispensing apparatus, specifically the dropper tip and cap. However, despite the stringent protocols, the microbial contamination of preserved and preservative-free eye drops, including the dropper tip, has been reported in operating rooms [14; 44; 47; 48] and hospital wards with variable durations of use [11; 47; 52; 55; 56]. The dropper tip and cap are often overlooked as potential sources of microbial contamination and cross-contamination [8; 20; 24; 28; 43; 50]. The aforementioned review highlighted the role of the dropper tip and cap in microbial contamination by direct contact with the eye or through the eye drops when they pass through the tip, which ranged between 7.7% and 100% of tested samples [8]. The present study confirmed these findings.