1 Introduction

Cataract surgery is the most common worldwide eye operation [1]. The procedure is safe and standardized, but severe postoperative complication has been reported [2, 3]. The most devastating and feared complication is endophthalmitis, a microbial infection of the eye during or after surgery [4]. Prophylaxis against postsurgical endophthalmitis is topical antibiotic therapy. However, drug abuse favors antibiotic resistance leading to a medical emergency [5]. Therefore, contemporary research focuses on new effective drug development for preoperative antisepsis.

The European Society of Cataract and Refractive Surgeons (ESCRS) [6] and the American Academy of Ophthalmology (AAO) [7] report that topical 5% povidone-iodine (PI) solution is the suitable antisepsis prophylactic method [8], due to wide-spectrum antimicrobial activity, absence of resistance and low cost. In a recent study, Tognetto et al. compared, in vitro, PI with two different antiseptic ophthalmic preparations composed of ozonated oil and chlorhexidine, respectively [9]. They demonstrated that PI solutions have a very rapid antiseptic activity, reducing the number of viable cells for all the tested strains under the detectable microbial load already after 1 min exposure. In contrast, both liposome-vehiculated ozonated oil and chlorhexidine-containing ophthalmic solution showed a weaker killing activity and, also, limited to few microorganisms. Grandi et al. studied, in vitro, the antimicrobial activity of ozonated oil eyedrop against multidrug-resistant bacteria and found interesting results about the timing of bacterial growth inhibition, essential constant to define an in vivo drug administration approach. Information about cells toxicity were out of studies’ goals [10]. Prophylactic agents with low ocular toxicity are limited, which warrants further research to reduce the incidence of endophthalmitis after cataract surgery. Natural compounds are good alternatives, where flavonoids have shown significant antibacterial activity and free radical scavenging. Citrus extract in liposomal form, composed of citrus bioflavonoids, has been described as a natural, non-toxic, chemical-free antiseptic agent with broad-spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria [11].

A new commercial ocular formulation (Oftasecur Ocular Spray, OFFHEALTH S.p.a., Florence, Italy) composed of 0.2% Biosecur liposomes, 0.15%, hypromellose, and other compounds, has been developed and introduced into the market as a possible presurgical treatment due to its antiseptic activity. An ocular spray delivers the molecule droplets to the eyelid margin, allowing the drug to mix with the tear film at the eyelid opening. Vagge et al. demonstrated the Oftasecur effectiveness in infection prevention in IVTs setting [12].

The aim of this study is to assess and validate the antiseptic activity of this new liposomal ophthalmic spray as a preoperative prophylactic treatment in patients undergoing cataract intervention.

2 Methods

2.1 Study design

A prospective, multicenter study was conducted from November 2021 to May 2022 at five eye hospitals in Italy, including Cardarelli Hospital, Ospedale del Mare, Santa Maria Delle Grazie Hospital, San Giuseppe Moscati Hospital and Villa dei Fiori. The study is in line with the principles of the Declaration of Helsinki and has been approved by the Ethics Committee of the University of Molise (24/22, October 2022). Informed consent was obtained from all patients in accordance with the ethical guidelines.

2.2 Participants

All patients scheduled for cataract surgery were screened for eligibility. Exclusion criteria were: malposition of the eyelids, ocular surface disease, presence of ocular infection, use of a topical antibiotic within the 12 weeks prior to enrollment in the study, and a known allergy to one or more components of Oftasecur. Participating patients were instructed to spray Oftasecur three times daily on the eye scheduled for surgery 3 days prior to cataract surgery (T0). All patients were examined at the beginning of the study (T0) and on the day of surgery (T1). At T0, each patient underwent a complete eye examination, including slit lamp biomicroscopy, fundus examination and biometry to calculate IOL power, endothelial cell count and conjunctival swabs. All swabs were sent to the local hospital laboratories within 24 h of collection.

2.3 Collection of conjunctival samples

For each eye, two conjunctival swabs were collected at T0 and T1. A sterile cotton swab was used for sample collection by rubbing the swab from the medial to the lateral side of the inferior fornix conjunctival sac through eversion of the lower eyelids, completely rotating the swab over the conjunctiva, without anesthesia [13]. On accidental swab contamination due to contact with lids, lashes, or other surrounding structures, the swab was excluded and repeated. At T1, the same procedure was performed before surgical disinfection in the operating room.

2.4 Microbiological analysis

After the swabbing procedure, swabs were put in glass tubes containing 5 mL of Brain Hearth Infusion (BHI) broth (Thermo Fisher Scientific, Waltham, Massachusetts, USA) and vigorously vortexed. For each tube, aliquots were plated on chocolate-enriched agar plates (VAKUTEST Kima), and plates were incubated at 37 °C for 48 h in 5% CO2. Quantitative determination of microbial loads was performed by the plate count method for 117 out of 147 patients. Qualitative evaluation of the swab content was performed for all patients identifying the isolated species by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) with Flex Control TM 1.1 (Bruker Daltonics, Bremen, Germany). Briefly, a well-isolated colony was spotted on the MALDI plate and treated with 1 μL of ethanol, 1 μL of formic acid, and 1 μL of acetonitrile. 1 μL of saturated α-cyano-4-hydroxycinnamic acid was spread on the plate, air-dried, and placed in the instrument. Spectral analyses were carried out by the MALDI Biotyper 3.0 (BDAL, Bruker Daltonics, Bremen, Germany) by standard pattern matching with a default setting.

2.5 Statistical analysis

Both statistical analysis and graphs were carried out on GraphPad Prism version 8.0.2 (GraphPad Software Inc., USA, https://www.graphpad.com/scientific-software/prism/). The two-tailed Student’s t-test for paired data was used to compare the CFU/mL (colony-forming unit for milliliter) obtained before Oftasecur treatment against those obtained after Oftasecur treatment.

3 Results

A total of 147 eyes of 147 patients (76 males, 71 females, mean age 70.74 ± Standard Deviation 9.41 years) enrolled for cataract intervention were tested. Prior to Oftasecur treatment, 86 patients (58.5%) had detectable microbial loads in the eye to treat, while 61 patient’s swabs showed no microbes (41.5%, Fig. 1).

Fig. 1
figure 1

Number of patients having positive or negative swabs before and after treatment with Oftasecur

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The most predominant contaminating species was Staphylococcus epidermidis, isolated from 58 patients, followed by other coagulase-negative Staphylococci in 14 patients (i.e., Staphylococcus capitis, Staphylococcus hominis, Staphylococcus lugdunensis, Staphylococcus warneri), Staphylococcus aureus in 6 patients, and Enterococcus faecalis in 1 patient. Two or three bacterial species were obtained from swabs collected from 7 patients. Sixty-one patients having a negative swab before treatment were still negative following the treatment with Oftasecur. An almost twofold reduction was observed among the positive patients receiving Oftasecur (Fig. 2).

Fig. 2
figure 2

Number of positive patients (total 60) having microbial loads ≥ 10 CFU/mL and < 10 CFU/ml in the conjunctival swabs before and after treatment with Oftasecur

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In fact, among the 86 patients showing microbial contamination of the eye before treatment, 44 showed negative results after treatment (51.2%). Among the 147 patients, quantitative determination of microbial loads was conducted on 117 patients, while swabs collected from 30 patients were only qualitatively analyzed to identify the contained species. Quantitative data analysis of 117 patients resulted in 60 patients resulting positive before Oftasecur treatment (51.3%), while no growth was obtained from swabs of 57 patients (48.7%). Twenty-five out of 60 patients had microbial loads lower than 10 CFU/mL before the treatment. These loads were almost the same or were reduced after Oftasecur treatment. Thirty-five out of 60 patients had microbial loads greater than or equal to 10 CFU/mL and lower than 100 CFU/ml before treatment. After treatment, the loads of 23 patients were lower than 10 CFU/mL, while 12 patients presented microbial loads between 10 and 100 CFU/ml. Figure 3 shows the variation of microbial load after Oftasecur treatment in the group of patients who presented a pre-treatment bacterial count equal to or superior to 100 CFU/ml.

Fig. 3
figure 3

Variation of microbial loads after Oftasecur treatment in the patients who presented pre-treatment bacterial counts equal to or greater than 100 CFU/ml. ***, P < 0.001

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A significant reduction in the bacterial loads after Oftasecur treatment was observed (p < 0.001), indicating the efficacy of Oftasecur in reducing bacterial contamination of the eye. No adverse reactions were recorded after topical treatment with the tested spray.

4 Discussion

Ophthalmic microbial infection post-cataract surgery has been reported as burdensome for both patients and surgeons. Therefore, we evaluated the efficiency of Oftasecur in reducing microbial encountered post-cataract surgery. Our multicenter, prospective study proved the efficacy of prophylactic treatment with Oftasecur spray-positive bacterial growth from conjunctival swabs in patients undergoing cataract surgery.

Unless surgical techniques improve and good clinical practice in postoperative follow-up is maintained, endophthalmitis will remain the most feared eye surgery complication. The two mainstream approaches to reduce postoperative endophthalmitis in cataract surgery include intracameral antibiotics during surgery [14] and topical antibiotic postoperative treatment. Nasery et al. demonstrated that intracameral antibiotic injection is unrelated to bacterial resistance because a single highly concentrated dose of antibiotic injected into a physiologically isolated space is unlikely to promote bacterial resistance [15]. By contrast, repeated and sporadic instillation of topical antibiotics on a rich bacterial ocular surface has been shown to induce the development of resistance [16].

Antibiotic resistance has become a global medical emergency due to drug abuse irrespective of infection status. Although endophthalmitis is rare, it still represents a sight-threatening complication. Therefore, endophthalmitis prevention with prophylaxis is a primary endpoint in patients' treatment. To overcome antibiotic resistance, researchers have increased their interest in evaluating new classes of drugs or compounds with low ocular toxicity, which might be helpful in prophylaxis. 5% PI solution is a universally accepted antiseptic and disinfectant agent for preoperative preparation in eye surgery, according to the guidelines of the ESCRS [6] and AAO [7]. Musumeci et colleagues; demonstrated in vitro that 0.6% PI formulation is faster than 5% PI solution in reducing both Gram-positive and negative bacterial load [17]. Furthermore, Reibaldi et al. reported the effectiveness of the treatment with 0.6% PI in patients who underwent intravitreal injection [8]. Nevertheless, it is well known that PI may induce ocular surface toxicity [18, 19] and might be related to topical allergies [20]. Therefore, other antiseptic commercial ophthalmic solutions have been investigated and compared to PI [9, 21, 22]. The ELOOM study demonstrated that topical liposomal ozonized oil reduced the microbial load after topical administration in a large study population, with over 90% of swabs resulting in negative after treatment [23].

In this context, Oftasecur may represent a valid prophylactic antiseptic adjuvant treatment in reducing the risk of postoperative endophthalmitis. Oftasecur comprises natural components, bioflavonoids, antioxidants, and free radical scavengers [24]. Recently, Mencucci and colleagues demonstrated that Biosecur inside liposome has broad antimicrobial activity in vitro against Candida albicans, as well as Gram-positive and Gram-negative bacteria, including antibiotic-resistant S. aureus and S. epidermidis. The data showed an optimal tolerability profile [11]. We recorded a significant decrease in the microbial load in patients treated with Oftasecur after the prophylactic treatment complementing previous studies. The most predominant contaminating species were Staphylococcus epidermidis, other coagulase-negative Staphylococci, Staphylococcus aureus, and Enterococcus faecalis. Conforming to the protocols reported in the literature, the patients enrolled in our study performed three daily applications, for three days, of Oftasecur in the eye to be operated on [23]. When tested at T1, over 50% of the swabs tested negative after prophylaxis. In vivo, Oftasecur presents a wide range of antibacterial activity. No ocular adverse reactions were recorded during the treatment and on T1 evaluation.

The study has few limitations. For one, the non-randomized design without a well-defined control group. Secondly, quantitative swab analysis was not performed on all the enrolled patients. The third possible limitation was variable patients’ compliance with the treatment schedule, which is necessary to take into account. Related to this point, we tried to improve the best patients’ compliance and reduce associated bias giving a diary to record administration time and possible ocular discomfort. In addition, Oftasecur is a spray formulation, easy to apply on your own. As a consequent of the effort to establish the correct administration of the treatment and the simple application way, we are quite confident that all the patients were compliant to the assigned house protocol.

This study was not conceived to demonstrate a reduction of endophthalmitis incidence after Oftasecur treatment. To achieve this goal larger population and a multinational study group are necessary. Therefore, we do not include any data about incidence of postoperative infection in this paper. Furthermore, this study was not designed to compare Oftasecur with other antiseptic products already on the market in terms of efficacy, safety and cost. Comparative data on the costs of the therapy were not considered. The comparative aspect that can be extrapolated from the collected data is that the administration of Oftasecur eye drops is not associated with local adverse effects. All patients were interviewed following therapy, and none reported any adverse events. In addition, no signs of adverse events were noted at the follow-up examination at T1, i.e. before the surgery. In literature, Mencucci et al. have shown that instillation of Oftasecur has an excellent tolerability profile in vitro, without cytotoxicity on conjunctival and corneal epithelial cells, at the diluted doses of the commercial product [11]. Of course, future studies should focus on randomized studies to overcome the highlighted limits to compare Oftasecur to other commercial antisepsis solutions.

In conclusion, we demonstrated the efficacy and the safety profile of Oftasecur spray as a preoperative prophylactic treatment in reducing conjunctival bacterial load in patients undergoing cataract surgery.