https://biointerfaceresearch.com/ 5638 Article Volume 12, Issue 4, 2022, 5638 - 5646 https://doi.org/10.33263/BRIAC124.56385646 Evaluation of Excreta/Secreta of Lucilia sericata Larvae as a New Antibacterial Candidate for Treatment of MRSA Ocular Infection Hamed Zare 1 , Khosrow Jadidi 2 , Gholamreza Farnoosh 3 , Maryam Hosseindokht 1 , Marek Kieliszek 4 , Hossein Aghamollaei 2,* 1 Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran; maryam68128@gmail.com (M.H.); 2 Chemical Injuries Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical, Tehran, Iran; kh.jadidi@gmail.com (K.J.); 3 Applied Biotechnology Research Centre, Baqiyatallah University of Medical Sciences, Tehran, Iran; rzfarnoosh@yahoo.com (G.F.); 4 Department of Food Biotechnology and Microbiology, Institute of Food Sciences, Warsaw University of Life Sciences- SGGW, Warsaw, Poland; marek_kieliszek@sggw.edu.pl (M.K.); * Correspondence: aghamolaei22@gmail.com (H.A.) Scopus Author ID 55053606400 (H.A.) 55445614900 (H.Z.) Received: 28.06.2021; Revised: 15.08.2021; Accepted: 18.08.2021; Published: 21.10.2021 Abstract: Staphylococcus aureus is the most serious cause of bacterial keratitis in most populations. Due to the resistance of this bacteria to methicillin (MRSA), the novel antimicrobial component is required for novel treatments for keratitis. Excretions/secretions (ES) from larvae of Lucilia sericata (maggot) have antibacterial activity against a number of bacteria. Around 500 larvae were washed with 1 mL of sterile water every hour for ES development. Bactericidal activity of ES was examined by time killing assay. MRSA strain was injected intrastromal into rabbit corneas. The rabbits have been split into three categories, including artificial tear, gentamicin, and maggot ES. Following, the eyes were clinically examined by a slit lamp. This evaluation included the conjunctiva, iris, and cornea. Lastly, the cornea of rabbits was collected for bacterial colony counts. After statistical analysis by ANOVA, it was found that gentamicin and ES, significantly reduced ocular infections in rabbits. Comparisons of corneal opacity scores with Mann–Whitney U-test showed a decreasing trend of therapeutic effects as shown below: gentamicin˃ES˃control. Gentamicin and ES significantly decrease CFU (number of colony-forming units) compared with the control. The mean bacterial count (log CFU/mL) from corneal culture for ES, gentamicin, and untreated groups were 6.04, 5.0, and 8.9, respectively (P≤0.05). In conclusion, the extraction of maggot larvae is useful in treating keratitis mediated by MRSA. Keywords: Staphylococcus aureus; maggot; antibacterial; ocular infection. © 2021 by the authors. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). 1. Introduction Bacterial keratitis is one of the most famous eye infections [1,2]. Staphylococcus aureus is the most serious cause of bacterial keratitis in most populations [1-4]. Individuals with contact lenses, persons in old populations, people with diabetes, patients with AIDS, and epithelial trauma caused by means of foreign bodies, are the major groups sensitive to Staphylococcus Keratitis [3,5]. Immunological and pathological examinations have shown bacterial products, and host-associated factors destroy the cornea in keratitis [1,3,5]. S. aureus