METHODS AND PROTOCOLS In vitro activity of alpha-mangostin in killing and eradicating Staphylococcus epidermidis RP62A biofilms Murugesan Sivaranjani 1 & Manivannan Prakash 1 & Shanmugaraj Gowrishankar 1 & Janarthanam Rathna 1 & Shunmugiah Karutha Pandian 1 & Arumugam Veera Ravi 1 Received: 19 December 2016 /Revised: 14 February 2017 /Accepted: 7 March 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract Alpha-mangostin (α-MG) has been reported to be an effective antibacterial agent against planktonic cells of many Gram-positive bacteria. However, the antibiofilm po- tency of α-MG remains unexplored till date. In this study, the antibiofilm and mature biofilm eradication ability of α- MG against Staphylococcus epidermidis RP62A (ATCC 35984) biofilms were evaluated. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of α-MG against S. epidermidis RP62A were found to be 1.25 and 5 μg/mL, respectively. α-MG exhibited a phe- nomenal concentration dependent rapid bactericidal activity (>4-log reduction within 5 min). In a multi-passage resistance analysis using S. epidermidis, no development of resistance to α-MG as well as antibiotics was observed in its habituation. α-MG at its 1/2 MIC effectively inhibited the initial biofilm formation of S. epidermidis, which was further confirmed through scanning electron microscopic (SEM) analysis that portrayed a lucid reduction in the aggregation and the spread of biofilm. The crystal violet staining and viable cell quantifi- cation results confirmed the eradication of preformed imma- ture and mature biofilms of S. epidermidis by α-MG in a concentration dependent manner. Besides, the biofilm eradi- cation ability was also confirmed through SEM and live/dead BacLight staining using confocal laser scanning microscopy (CLSM). Thus, the present study exemplifies that α-MG could plausibly assist to eliminate biofilm infections associat- ed with multidrug-resistance staphylococci. Keywords Staphylococcus epidermidis . Alpha-mangostin . Biofilm . Resistance . Bactericidal Introduction Staphylococcus epidermidis beyond its local homoeostasis characteristics on human skin as a commensal flora, it has been well recognized for the most frequent cause of health care-associated bloodstream infections and biomaterial- associated infections (Otto 2012; Ziebuhr et al. 2006). S. epidermidis are the utmost notable member of coagulase- negative staphylococcal group (CoNS), as nearly 80% of CoNS isolates were S. epidermidis. It is ranked first and third in causing native valve infective endocarditis (NVIE) and prosthetic valve infective endocarditis (PVIE), respectively. Despite its lesser virulence, it has been well adapted to colo- nize and establish highly structured, multilayered robust biofilms on any implanted biomaterial surfaces such as vas- cular catheters, prosthetic joints, and artificial heart valves (Qin et al. 2007). In S. epidermidis, biofilm formation is the most imperative virulence trait making this commensal inhabitant as hazardous to implanted medical device usage. In the intricate architecture of biofilm, bacterial cells encase themselves and escape from host defense mechanisms as well as antimicrobial agents, which eventually leads to chronic and refractory infections (Lefebvre et al. 2016; Nilsson et al. 2016; Falsetta et al. 2012). Besides, S. epidermidis infections associated with biofilms persist until the removal or subsequent replacement of implantable medical devices, resulting in further distress and cost (Donlan and Costerton 2002). Furthermore, this Electronic supplementary material The online version of this article (doi:10.1007/s00253-017-8231-7) contains supplementary material, which is available to authorized users. * Arumugam Veera Ravi aveeraravi@rediffmail.com 1 Department of Biotechnology, Alagappa University, Science Campus, Karaikudi, Tamil Nadu 630 003, India Appl Microbiol Biotechnol DOI 10.1007/s00253-017-8231-7