Indonesian Journal of Biotechnology, June, 2006 Vol. 11, No. 1, pp. 870-877 870 the microbial balance of gastrointestinal tract (Perdigon et al., 1995; Kaminogawa et al., 2004). Probiotic is defined as live microorganism added to food that give benefit to host by increasing the microbial balance of intestinal (Ziemer et al., 1998). Another definition stated that probiotic is live microorganism which is consumed by oral and give health effect (Losada et al., 2002; Champagne et al., 2005). Some lactic acid bacteria (LAB) have been studied as potent probiotic. Current researchs of probiotic focus on the capability of the products to increase immune system and immune response mechanism which is thought to play an important role to protect the body from any Effect of Probiotic Lactobacillus sp. Dad13 on Humoral Immune Response of Balb/C Mice Infected with Salmonella typhimurium 1 2 13* Ika Dyah Kusumawati , Eni Harmayani and Widya Asmara 1. Reaserch Center for Biotechnology, Gadjah Mada University, Yogyakarta, Indonesia. 2. Faculty of Agriculture Technology, Gadjah Mada University, Yogyakarta, Indonesia. 3. Faculty of Veterinary Medicine, Gadjah Mada University, Yogyakarta, Indonesia. Abstract An indigenous strain of lactic acid bacterium (LAB) identified as Lactobacillus spp. Dad13 (Dad13), isolated from traditional fermented buffalo milk, was found to be potential as probiotic. The aim of this research was to study the effect of probiotic Dad13 on humoral immune response of Balb/ C mice infected with Salmonella typhimurium. The specific objective was to find out the effect of different Dad13 consumption time (before and along with infection of S. typhimurium) on the humoral immune response of Balb/ C mice. The experiment was conducted by in vivo trial on 20 males of Balb/ C mice, age of 6-8 weeks, fed with AIN-93 standard diet. The mice were assigned into 4 groups. Each group received the following treatments, ie. Dad13 only, Dad13 before infection, Dad13 along with infection and 10 Salmonella infection only. A volume of 100 μl Dad13 cell suspensions (10 CFU/ ml) were given by oral forced feeding daily for a week, at week 3 for group before infection and at week 4 for group of Dad13 only and Dad13 along with 9 infection. Salmonella infection (10 CFU/ ml) was given once orally at week 4 to all groups except group treated with Dad13 only. The humoral immune response of Balb/ C mice was detected 2 weeks after infection by measuring the titers of IgG and IgA specific from serum and mucosal intestinal liquid samples using Enzyme-linked Immunosorbent Assay (ELISA) method. The result indicated that humoral immune response of Balb/ C mice consuming Dad13 before and along with Salmonella infection were significantly different (p<0.05). Dad13 consumption along with Salmonella infection increased circulated IgG and IgA as well as secretory IgA. It can be concluded that Dad13 probiotic feeding along with infection increased humoral immune response more significantly compared to that before infection. Key words : Probiotic, Lactobacillus sp. Dad13, Immune response, Salmonella typhimurium Introduction Food borne Salmonellosis is still a big problem in Indonesia. Salmonella typhimurium is one of the pathogenic Salmonella species which causes the diseases. Besides the treatment with antibiotics, functional food such as probiotic is currently considered as an alternative way to reduce the number of diarrhea cases which are caused by food contamination. Probiotic gives health effect by improving Corresponding author: Widya Asmara, Research Center for Biotechnology, Gadjah Mada University, Jl. Teknika Utara, Barek, Sleman Yogyakarta, 55281. Tel: 62-274-564305; Fax: 62-274-520842; E-mail: wied_as@ugm.ac.id