Epigallocatechin Gallate Inhibits Biofilm Formation by Ocular Staphylococcal Isolates

Abstract

Epigallocatechin gallate (EGCg), the main polyphenol component of green tea, has several antibacterial properties. Here we show that sub-MICs of EGCg appear to decrease slime production, therefore inhibiting biofilm formation by ocular staphylococcal isolates previously characterized for the presence of ica genes by the Congo red agar plate assay and for adhesion to microtiter plates.Biofilm formation is a three-stage process (6) that significantly contributes to the pathogenesis of staphylococcal infections. The first stage, docking, is mainly due to hydrophobic interactions, whereas the next two stages, locking and maturation, are mediated by capsular polysaccharide adhesins, PIA (polysaccharide intercellular adhesin) and PNAG (poly-Nacetylglucosamine polysaccharide), both of which are synthesized by the gene products of the ica operon (icaADBC), with the main contribution coming from an N-acetylglucosaminyltransferase encoded by the icaA gene (5, 12). The expression of the icaA gene alone results in low enzymatic activity, but coexpression with icaD leads to a significant increase in activity (8).Green tea polyphenols and, more specifically, epigallocatechin gallate (EGCg) are known to possess both direct bactericidal activity (18,19) and the ability to potentiate the effects of certain antibiotics (15,16,17,21). Moreover, they have already been shown to have at least an indirect influence on biofilm production, in that they can retard the formation of dental plaque (9,11,20).In this study, we have investigated the effects of sub-MICs of EGCg (99% pure; Sigma) ( Fig. 1A, inset) on biofilm formation by 20 different ocular staphylococcal isolates derived from patients with community-acquired ocular infections and belonging to our private collection. The different isolates included 8 Staphylococcus aureus isolates and 12 Staphylococcus epidermidis isolates. Moreover, two American Type Culture Collection strains (S. epidermidis ATCC 35984 and S. epidermidis ATCC 12228) were used as reference controls. Table 1 summarizes the characterization of bacterial isolates for biofilm production. The MIC of EGCg for each strain was determined in tryptic soy broth (TSB) by a broth dilution method according to the guidelines of the CLSI (formerly the NCCLS) (13). The quality of the lot of EGCg was controlled by reverse-phase high-pressure liquid chromatography (HPLC) and showed just one single, sharp peak, suggesting a very high degree of purity (Fig. 1A). The MICs obtained ranged from 125 to 500 mg/ml, similar to that which we reported recently (17); however, they were slightly higher than those already described by other authors (22, 24).Each ocular isolate was then characterized for biofilm-related properties. Biofilm-forming ability was tested by determination of adhesion to microtiter plates (5) and was quantitated by safranin staining and reading of the absorbance at 492 nm. The biofilm production of the different strains was then arbitrarily classified as strong (optical density [OD], Ͼ0.9 OD), medium (0.6 Ͻ OD Ͻ 0.9),...

Antimicrobial activity of green tea extract against isolates of methicillin–resistant Staphylococcus aureus and multi–drug resistant Pseudomonas aeruginosa

“…The properties of green tea which inhibit bacterial growth are mainly related to their polyphenolic components including epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate against various Gram-positive and Gram-negative bacteria [22,23] . Green tea was also reported to have a synergistic effect with β-lactam antibiotics against MRSA [24][25][26][27][28] , It was also reported that the main component of tea polyphenols, epigallocatechin gallate can reverse methicillin resistance of MRSA by inhibiting the synthesis of PBP2 [29] , Epigallocatechin gallate not only increases the activity of β-lactams but also increases the activity of non-β-lactam cell wall biosynthesis inhibitors [26] .…”

Correlation between Biofilm Production and Bacterial Urinary Tract Infections: New Therapeutic Approach

“…Then plates were inoculated and incubated aerobically for 24 to 48 h at 37°C. Presence of black colonies with a dry crystalline revealed that bacteria are biofilm producing and non-producers remain pink (Freeman et al, 1989 andBlanco et al, 2005) Microtiter plate (MtP) assay The test was performed according to Christensen et al (1982). The Overnight bacterial cultures were diluted 1:10 with Trypticase Soy Broth, 96-well microtiter plates were used and seeded with 200 µL per well.…”

Antibacterial Effects of Green Tea Polyphenols on Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

“…Previous studies have reported that green tea polyphenols (TPP), collectively termed catechins including epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), have bactericidal activity against various Gram-positive and Gram-negative bacteria [3,13,23]. Recently, EGCG was reported to act synergistically with various b-lactam antibiotics against MRSA [10-12, 21, 22].…”