INTRODUCTION World Health Organization (2004) reported that infectious diseases are a major cause of morbidity and mortality worldwide and bacterial infection causes high rate of mortality in human population (Farias et al., 2000). The enhanced treatment of infectious diseases by microbicide has limitations because of its changing patterns of resistance in pathogens and side effects. These limitations demand for the identification of new antimicrobial compounds derived from natural sources especially from marine (Ballantine et al., 1987).Marine seaweeds are rich source of structurally novel and biologically active metabolites. Secondary and primary metabolites isolated from seaweeds are potentially active in the pharmaceutical industry against human and other diseases (Farias et al., 2000). Most of the secondary metabolites of marine seaweeds such as flavonoids, terpenoids, alkaloids and phenolic compounds show wide range of anti-bacterial activities against the human pathogens ( Thirumaran et al., 2006) and recent research implies that polysaccharides like inulin, oligo-fructose, galacto oligosaccharides and lactilose can also act as potent prebiotic compounds against pathogenic microbes in humans.The antimicrobial activity of seaweeds in the coastal area of Tamil Nadu is still needs to be explored. Sargassum wightii belongs to brown seaweeds and are widely found in south Indian coastal belt with remarkable biological activities.Bacillus cereus is a Gram-positive, rod-shaped aerobic bacterium with endospore (Todar, 2008) and can multiply quickly even at room temperature. B. cereus is responsible for a minority (2-5%) of food borne diseases (Todar, 2008;Davis, 2010), causing severe nausea, vomiting and diarrhea, aggressive than necrotizing fasciitis. Food poisoning is a major health problem, affecting both industrialized and developing countries.Objective of the present study was to screen the crude solvent extracts of S. wightii against the food borne pathogen B. cereus.
MATERIALS AND METHODS
Antibacterial assaysBacterial culture B. cereus was collected from the Rajah Muthiah Medical College, Annamalai University, Tamil Nadu, India. Collected strain was grown in Trypticase soy-polymyxin broth under aerobic conditions at 37°C in a rotary shaker at 200 rpm to reach exponential growth.
Screening of antibacterial activityCrude petroleum ether, chloroform, acetone and ethanol extracts of the seaweed S. wightii were obtained by sequential solvent extraction method using a soxhlet. The antibacterial activity of crude extracts was performed by agar plate well diffusion assay on Mueller Hinton Agar (Marudhupandi and AjithKumar, 2013). Mueller Hinton agar media was prepared, sterilized and poured into sterile Petri dishes. Wells of 6 mm diameter were made on the agar plates by using sterilized well cutter. Inoculum in exponential phase of growth, equivalent to a 0.5 McFarland standard was swabbed on to the surface of the agar. Crude extracts of the solvents (petroleum ether, chloroform, acetone and ethanol) were prep...
