ABSTRACT
Nowadays, probiotics have been widely consumed as supplementary food for their health benefits. However, safetyevaluation for many probiotic bacteria is still lacking. Furthermore, health benefits conferred by probiotics depend onthe strains used in producing probiotic products. Therefore, it is important to examine oral toxicity of newly isolatedLactobacillus casei (Lb. casei) C1. A total of 32 Wistar (WIS) rats were divided into acute (single dose) and subacuteoral toxicity (28-days repeated dose) groups. Rats in each group were further divided into control group which receivedphosphate buffer saline (PBS) orally and treatment group that was administered orally with Lb. casei C1 (1011 CFU/ml).For acute oral toxicity, treatment was performed on day-1 and the effects were monitored subsequently for 14 days. Forsubacute oral toxicity, treatment was given daily for 28 days and the effects were observed throughout the experimentalperiod. Body weight, food and water intake of the rats were recorded. Rats in acute and subscute groups were sacrificedon day-15 and day-29, respectively. Serum was collected to determine the levels of total protein, malondialdehyde (MDA),alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH) and creatinine. Organs were alsoharvested for histological examination. There were no significant differences (p > 0.05) in body weight, food and waterintake between the control and treated rats in acute oral toxicity group. There were also no significant differences in theblood cell count, levels of total protein, MDA, LDH and creatinine between the control and treated rats. Similar findingswere recorded for the subacute oral toxicity group, except that the levels of ALT and AST which were significantly different(p < 0.05). When observed under a light microscope, there were no morphological changes detected in the kidney, liverand ileum of treated rats as compared to control rats in both of the experimental groups. In conclusion, Lb. casei C1exhibited no toxic effects in Wistar rats hence safe to be consumed orally.