# Evaluating and Managing the Microbial Contamination of Eye Drops: A Two-Phase Hospital-Based Study
## 3 Results
### Phase 1: Assessment of Microbiological Contamination In-Use Eye Drops
#### 3.1.2 Collection and Culture of In-Use Specimens  
Over four months, 157 eye drops produced by UPSO2 and used by out-patients and nurses were collected, with 110 eye drops analyzed (hospitalization (65%) versus patients (35%)) and 47 discarded due to a delay in the period between eye drop collection and the analysis of samples. In-use eye drops collected from the hospital contained antibiotics (90%), including amikacin, piperacillin, vancomycin, and other anti-infective agents (10%), including voriconazole, amphotericin B, and anti-amebic agents. Eye drops collected from patients contained immunosuppression(87%), notably cyclosporine, antibiotics (2%, piperacillin), and other anti-infective agents (11%), including voriconazole and amphotericin B. Contamination Rate and Characteristics of Contaminated Bottles  
Out of 110 collected eye drops, 36 (33%) were contaminated, as follows: 24 (22%) eye drops at the cap and dropper tip levels simultaneously, 9 (8.1%) eye drops solely at the cap level, and 3 (2.7%) solely at the dropper tip level. The microbial loads varied between 1 CFU and 10\({}^{2}\) CFU per dropper tip/cap. Number of Microorganisms Recovered from Eye Drop Tip and Inner Cap  
* The three contaminated eye drop tips and inner caps used during hospitalization had a microbial load of less than 10 CFU. Out of the 33 contaminated eye drops collected from patients, 20% of cultured dropper tips and inner caps showed a microbial load of around 10\({}^{2}\) CFU, and 20% had a high level of contamination (>330 CFU). Only one bottle's residual content showed microbial contamination. * The identified microorganisms included commensal germs from the environment and human skin flora. The used eye drops collected from the hospital and patients showed microbial contamination of the eye drop tips and caps with _Staphylococcus epidermidis_ and _Genotrophomonas maltophilia_. All other detected microorganisms originated only from patients using eye drops. The most frequently detected microorganisms from used eye drop tips and caps were Gram-positive bacteria (GPB), such as _Microoccus luteus_ (n = 14) and other GPB considered part of the skin flora, including _Staphylococcus hominis_ (n = 5), _Staphylococcus capitis_ (n = 4), _Kocuria species_ (n = 6), _Staphylococcus aureus_ (n = 3), _Staphylococcus haemolyticus_ (n = 3), _Staphylococcus varneri_ (n = 2), _Staphylococcus saprophvticus_ (n = 2), _Staphylococcus auricularis_ (n = 1), _Staphylococcus pasteuri_ (n = 1), _Corynebacterium species_ (n = 2), _Microbacterium aurum_ (n = 2), _Aerococcus viridans_ (n = 1), and _Dolosiranulum pigrum_ (n = 1). Isolated GPB found in the environment included _Bacillus cereus_ (n = 2), _Bacillus thuringiensis_ (n = 1), _Bacillus licheniformis_ (n = 1), _Janibacter hoplei_ (n = 2), _Lysinibacillus_ spp. (n = 1), and _Streptomyces violacoruber_ (n = 1). Gram-negative bacteria (GNB) contaminants included _Stentrophomonas maltophilia_ (n = 3), _Moraxella osloensis_ (n = 2), _Pseudomonas oryzaehabitatus_ (n = 1), _Acinetobacter lwoffii_ (n = 1), and _Roseomonas mucosa_ (n = 4). Stertility tests showed only one positive result (in-use eye drop bottle collected from a patient) involving the eye drop tip and inner cap contaminated with _Candida parapsilosis_ (n = 1). The residual content's microbial contaminants were _Candida parapsilosis_ and _Lysinibacillus_ spp. (n = 1). Phase 2: Evaluation of the Practical and Antimicrobial Properties of Pylote SAS Antimicrobial Technology  
3.2.1. Validation of the Practical Application of Activated Rispharm(tm)
* Use of Activated Rispharm(tm): Minor discrepancies were noted compared to the bottles routinely used. There were no significant differences in the bottleneck size or its adaptability to the filling process. Operators unanimously acknowledged the challenge of inserting the dropper tip. The operators recommended the implementation of a more robust capping procedure to ensure secure bottle closure, with a particular focus on addressing any vacuum occurrence before the final screwing movement.