Antibiotic Sensitivity Of Acid Stressed Probiotic Lactobacillus Acidophilus Ncdc 291

摘要

LAB (Lactic Acid Bacteria)-Lactobacillus acidophilus, a major inhabitant of gastrointestinal tract of human beings is used as a probiotic. Antibiotics taken during illness not only kill the disease causing microorganisms but also disrupt the normal microbial balance of the gut leading to a number of side effects and encouraging the patients to restore their natural gut microflora with the intake of probiotics. A well known probiotic Lactobacillus acidophilus NCDC 291 was used in the present study and its resistance towards antibiotics was determined at optimum pH and also by growing it under acid stressed conditions. Studies revealed that culture adapted to acid stressed conditions had increased resistance towards antibiotics than that grown at optimum pH. Introduction A well known proverb “health is wealth” has become the most important subject of concern with the modern world. Healthy lifestyle can be achieved with a nutritious diet, regular exercise etc. When it comes to health and diet, an increasing trend for food containing probiotics is in demand today. Probiotics are usually defined as microbial food supplements, that when administered in adequate amount exert beneficial effects on the host (Khalil et al., 2007).LAB (Lactic Acid Bacteria)-Lactobacillus acidophilus is a major inhabitant of gastrointestinal tract of human beings. It is used as a probiotic because it has tendency to adhere to the intestinal epithelial cells thereby colonizing the gut. It can survive harsh conditions in the stomach and can also deconjugate bile salts released in the intestine. It lowers pH in the gut making the environment unfavourable for the growth of pathogenic bacteria. Antibiotics taken during illness act as a double edged sword killing not only the disease causing microorganisms but also disrupting normal microbial balance of the gut. According to the latest statistics one in five persons taking antibiotics does not take full course of antibiotic therapy because of the side effects associated with it. Common antibiotic side effects include upset stomach, diarrhea, and vaginal infections etc which occur mainly because of the disturbed microbial load or normal bacterial flora of the patient. To overcome this problem supplementary diet including probiotics is a must. For this the antibiotic sensitivity of the probiotic microorganism holds foremost position. Lactobacilli show varied response towards different antibiotics. Increased resistance of the acid stressed culture provides us with a potent probiotic supplement that can withstand high acid conditions in the stomach and colonize the intestine further enhancing the immunity of the patient by discouraging the growth of pathogenic microorganisms. In the present study a well known probiotic i.e. Lactobacillus acidophilus NCDC 291 was taken and its potential to survive the antibiotic stress at optimum pH and of acid stressed culture was determined. Material and Methods Microbial culture of Lactobacillus acidophilus NCDC 291 was obtained from Dairy Microbiology division, National Dairy Research Institute, Karnal, India.Initially it was cultured in 12% (v/v) skimmed milk autoclaved at 15 psi for 30 min and incubated for 24 h at 37 °C. Curdling of milk marked the growth of L. acidophilus. Subsequent culturing was carried out by inoculating in readymade MRS medium (HIMEDIA), pH 6.5 ± 0.2 autoclaved at 15 psi for 15 min. This was followed by incubation for 24 h at 37 °C.Effect of pH on growth:Following the method of Joshi et al., (2006) pH of MRS medium was altered to 3.5, 4.5, 5.5, 6.5 and 7.5 using 0.1 N NaOH/ 0.1 N HCl. It was then inoculated @ of 1% (v/v) of overnight grown culture and incubated for 24 h at 37 °C. Absorbance was taken every 6 h at 600 nm and SPC was also recorded. Antibiotic sensitivity: Antibiotics namely Ampicillin, Erythromycin, Streptomycin, Vancomycin, Penicillin, Chloramphenicol and Tetracycline were chosen in the present study. Ampicillin, Vancomycin, Streptomycin