Full Communication Antimicrobial Activity of Two Propolis Samples Against Human Campylobacter jejuni Raffaella Campana, 1 Vania Patrone, 1 Ingrid Tarsilla Maria Franzini, 1 Giuseppe Diamantini, 2 Emanuela Vittoria, 1 and Wally Baffone 1 1 Istituto di Scienze Tossicologiche, Igienistiche ed Ambientali; and 2 Istituto di Chimica Farmaceutica, Universita` di Urbino ‘‘Carlo Bo,’’ Urbino, Italy ABSTRACT The aim of this study was to analyze the antimicrobial activity of two ethanolic extracts of propolis (EEPs) and selected flavonoids against 16 Campylobacter jejuni clinical isolates and several Gram-positive and Gram-negative human pathogens. The antimicrobial activity of EEPs and flavonoids was evaluated by the agar well diffusion method. The EEPs inhibited the growth of C. jejuni, Enterobacter faecalis, and Staphylococcus aureus. The most active flavonoid was galangin, with the highest percentage of sensitivity among C. jejuni strains (68.8%); lower percentages of sensitivity were observed for quercetin (50%). The minimal inhibitory concentrations ( MICs) of EEPs and flavonoids for C. jejuni isolates were determined by the agar dilution method. EEPs showed MIC values of 0.3125–0.156 mg=mL for all C. jejuni strains; galangin and quercetin gave MICs ranging from 0.250 to 0.125 mg=mL. Thus propolis preparations could be used as support to traditional therapy for Campylobacter infection, especially when the antibiotic agents show no activity against this microorganism. KEY WORDS:  agar well diffusion method  Campylobacter jejuni  galangin  Gram-negative bacteria  Gram-positive bacteria  minimal inhibitory concentrations  morin  propolis  quercetin INTRODUCTION P ropolis is a resinous hive product collected by honey- bees from various plant sources, like poplars, cherry trees, birches, and pine trees. Propolis, used by humans since ancient times, 1 has a broad spectrum of well-known biolog- ical activities, including anti-inflammatory, antimicrobial, antioxidative, and antiviral effects. 2–4 The antimicrobial ac- tivity of propolis has been demonstrated against bacterial and yeast pathogens isolated from human infection. 5,6 Several authors reported that propolis is active against Gram-positive bacteria but shows limited activity against Gram-negative bacteria. 7,8 Nevertheless, some authors re- ported propolis antimicrobial activity against Helicobacter pylori, 8,9 whereas there are very few data 10 about its effect on other Gram-negative pathogens such as Campylobacter jejuni, a major cause of enteric infection. 11–15 Normally, Campylobacter infections are self-limiting, and the treatment with antibiotics is therefore not generally recommended. 16 However, antimicrobial treatments are needed in individuals with invasive or very severe disease, such as Guillain-Barre ´ or Miller Fisher syndrome. 12 Immunocompromised patients, the very young and the very old, may be treated as well. In these cases, therapy may be complicated by the fact that antimicrobial resistance in Campylobacter isolates from human infections has become increasingly common. 17,18 Resistance rates, in fact, have increased significantly over the past 2 decades, primarily due to the extensive agricultural use of antimicrobial agents. 19,20 The aim of this study was to analyze the spectrum of antimicrobial activity of ethanolic extracts of two propolis samples and selected flavonoids on several human patho- genic bacteria. Moreover, their antimicrobial activity was tested on human C. jejuni strains in order to evaluate the suitability of propolis as a natural remedy to support con- ventional regimens in Campylobacter infections. MATERIALS AND METHODS Preparation of ethanolic extracts of propolis (EEPs) The propolis samples were collected from beehives in the Calabria region (Southern Italy) in September 2005 (sample 1) and the Emilia-Romagna region (Central Italy) in May 2006 (sample 2). The EEPs were prepared according to the method of Lu et al. 21 In brief, propolis samples were first cut into small pieces and ground. Twenty-five grams of each ground propolis was extracted with 250 mL of 80% ethanol by shaking (150 rpm) at 258C for 48 hours. The ethanolic ex- tract solutions, named EEP 1 and EEP 2, were then filtered Manuscript received 8 July 2008. Revision accepted 13 February 2009. Address correspondence to: Prof.ssa Wally Baffone, Istituto di Scienze Tossicologiche, Igienistiche ed Ambientali, Universita`di Urbino ‘‘Carlo Bo,’’ Via S. Chiara 27, Urbino, Italy, E-mail: wally.baffone@uniurb.it JOURNAL OF MEDICINAL FOOD J Med Food 12 (5) 2009, 1050–1056 # Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition DOI: 10.1089=jmf.2008.0173 1050