Arch Clin Infect Dis. 2019 February; 14(1):e65321. Published online 2019 March 2. doi: 10.5812/archcid.65321. Research Article Evaluation of Antibacterial Activity of Zataria multiflora Against the Expression of icaADB and aap Gene and Biofilm Formation in Staphylococcus epidermidis Zahra Mottaghiyan 1 , Mohammad Aghazadeh 1, * , Hamideh Mahmoodzadeh Hosseini 2 and Abbas Ali Imani Fooladi 2, ** 1 Immunology Research Center, TabrizUniversity of Medical Sciences, Tabriz, Iran 2 Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran * Corresponding author: Immunology Research Center, Tabriz University of Medical Sciences, Tehran, Iran. Email: aghazadeh@tbzmed.ac.ir ** Corresponding author: Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Vanak Sq. Molasadra St., P.O. Box: 19395-5487, Tehran, Iran. Tel: +98-2182482568, Fax: +98-2188068924, Email: imanifouladi.a@gmail.com Received 2017 December 19; Revised 2018 December 29; Accepted 2019 January 20. Abstract Background: This study aimed at evaluating the effect of the extract and essential oil of Zataria multiflora on reducing phenotypes and genotypes of biofilm formation in clinical isolates of Staphylococcus epidermidis. Methods: The ability to produce biofilm was evaluated by microtiter plate (MtP) for phenotype and through the presence of icaADB and aap by PCR for genotype among the 153 clinical isolates of Staphylococcus epidermidis. The impact of ethanol extract and essential oil of Zataria multiflora were measured on biofilm formation in phenotypic evaluation based on MtP and on the expression of ica operon and aap by real time-PCR. Results: The results showed that 71.2% of isolates were able to produce biofilms. The PCR results showed that 52.2% and 88.9% of the isolates had icaABD and aap, respectively. In addition, the relative mRNA expression of icaA, icaD, and aap genes were significantly re- duced compared to the negative control after treating the Staphylococcus epidermidis RP62A with subMIC concentration of essential oil and extract (P < 0.001). Conclusions: Given the significant inhibitory effect of the extract and essential oil of Zataria multiflora on biofilm formation, it seems that these substances are good options for studies related to controlling biofilm formation in Staphylococcus epidermidis Keywords: Biofilm, Staphylococcus epidermidis, Zataria multiflora 1. Background Staphylococcus epidermis is the most frequent cause of implanted medical device or catheter-related infections and it has caused an increase in resistance to different types of antibiotics in hospitals through its most signif- icant virulence factor, i.e. biofilm production. Polysac- charide intercellular adhesive (PIA) is a product of the ica operon and is strongly associated with staphylococcal cell surface and the main composition, which mediates cell to cell adhesion. The ica operon contains ica ADBC genes, which are required for PIA synthesis (1). Other pathways also contribute to biofilm formation in Staphylococcus epi- dermis independent of the ica operon, such as the biofilm accumulation associated protein (Aap) forming fibrillary structures on the cell surface (2). Zataria multiflora is a plant from the Labiatae fam- ily that grows in Iran, Pakistan, and Afghanistan. The traditional uses of Zataria multiflora include antiseptics, anesthetics, and antispasmodic (3). In this plant, the most antibacterial activity is related to essential oil with compounds including thymol and/or carvacrol, phenolic derivatives. The anti-biofilm activity of Zataria multiflora was reported against Pseudomonas aeroginosa and Listeria monocytogenes, and antibacterial activity of Zataria multi- flora was shown against Staphylococcus epidermidis strains, yet there is no study about the role of Zataria multiflora on inhibition of biofilm formation in Staphylococcus epider- midis isolates (4). Many studies have investigated the effect of different substances on biofilm production in Staphylococcus epi- dermis, including silver colloidal nanoparticles and Cas- sia alata leaves (5). The effect of Zataria multiflora Boiss on biofilm production in Staphylococcus epidermis has not Copyright © 2019, Archives of Clinical Infectious Diseases. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.