# Evaluating and Managing the Microbial Contamination of Eye Drops: A Two-Phase Hospital-Based Study
## 4 Discussion
These compounds with oxidative properties are rapidly biodegradable active molecules [94; 95; 96]. The oxidizing radicals produced at the microsphere surface lead, by direct contact, to the destruction of a broad spectrum of GPB and GNB, resistant bacteria, in addition to viruses (including those causing conjunctivitis), and have a lesser effect on fungi [90; 91]. The potent antimicrobial activity of microspheres is due to the sphericity coefficient of \(\geq\)0.75, characterized by a narrow distribution size and even distribution on integrated surfaces, where the determined distance between two microspheres is between 0.2 and 1 \(\upmu\)m [91]. The antimicrobial effect occurs in nanoseconds within a few nanometers of the incorporated surface without the release or consumption of the microspheres [91]. The antimicrobial activity of Pylote mineral microspheres is dose- and time-dependent [91]. Pylote technology has demonstrated high effectiveness in vitro, in vivo, and in situ and has shown sustainable effects under real-life and worst-scenario conditions. Previous tests [90] were undertaken according to the ISO 22196:2011, JIS Z 2801, ISO 20743:2021, and NF S90-700:2019 standards. In the present study, Activated RigharmTM eye drop containers, integrating Pylote technology into the dropper tips and inner caps, were tested against standard plastic containers. The inoculated bacteria and fungi were selected according to the literature review [8] and the recommendations of the _European Pharmacopoeia_ for testing antiseptic medicinal products [34]. Pylote technology has demonstrated effective antimicrobial activity in vitro against a wide range of microorganisms, including _S. aureus_ (NCTC 10788), _P. aeruginosa_ (NCTC 12924), and, to a lesser extent, _C. albicans_ (NCPF 3179) [91]. The inoculated microbial load of each microorganism was similar to that in the tests previously conducted. At baseline, standard eye drops collected from the patients and the hospital showed unlimited microbial growth of the two tested bacteria at the dropper tip and cap sites. The second phase showed that Activated RigharmTM packaging inoculated with _S. aureus_ and _P. aeruginosa_ exhibited more than one log reduction compared with the control, while the standard packaging showed unlimited growth. Although Pylote technology showed a higher reduction in microbial load in in vitro studies [91], these differences can be related to sampling, swabbing, the methodology of microbiological culture in vitro, and the surface type cultured (flat coupons versus dropper tips and caps). The methods applied in the in vitro study [91] consisted of recovering the microorganisms by dispersion on the plates, dilution, and culture in broth cultures, compared with the swabbing method used in this experiment. For _C. albicans_, there was no observed difference between the different types of packaging. A reduction of about 1 log was observed between the control and the packaging. The Pylote technology maintained a low level of contamination with the microorganisms. In this experiment, dilution was not undertaken, and although it may not have affected the reliability of the results, it could have further demonstrated the antimicrobial efficiency of the technology in preventing the contamination of the incorporated surfaces. A thirty-year literature review of dropper tip and cap microbial contamination found that _Staphylococcus_ spp. are the predominant microorganisms isolated from in-use eye drops [8]. In the present experiment, the results showed the high effectiveness of Pylote technology in reducing _S. aureus_ microbial load, while its effect on _P. aeruginosa_ was more limited compared to the control. Of note, standard packaging showed high microbial proliferation in the same conditions. The tested in-use eye drops in this study did not show any contamination with _P. aeruginosa_.