Streptococcus thermophilus and Lactobacillus bulgaricus are found in yoghurt, which is a commercialised version of dahi. It only contains those two strains of bacteria. In the homemade dahi or ones we get from local shops, the bacteria strain can vary, but is usually some strain of Lactobacillus bacteria. Streptococcus thermophilus and Lactobacillus bulgaricus.
Home Ask The World Which bacteria is found in curd? Methods Take a very small drop of yogurt with the toothpick and smear it for 2 to 3 seconds on the slide.
Place a small drop of methylene blue solution on a microscope slide optional. Wear gloves and do NOT allow children to handle methylene blue solution. Place a coverslip on top. Haemolytic capacity and antimicrobial susceptibility in vitro : None of the strains tested exhibited any sign of haemolysis when grown on blood agar for 24 h under anaerobic conditions. The strains were also tested for evidence of resistance to commonly used antimicrobial classes using antimicrobial disk diffusion and growth for 24 h.
All the tested strains were resistant to most of the antimicrobials tested including vancomycin, norfloxacin, ampicillin, chloramphenicol, gentamicin, rifampicin, tetracycline and amoxicillin-clavulanic acid Table III. All strains were sensitive to imipenem.
Intrinsic antimicrobial activity against pathogens : The intrinsic antimicrobial activity of the isolated strains was tested against four different pathogens using the well diffusion method. Fourteen of the 16 strains tested inhibited the growth of S. Typhimurium Fig. Five strains showed an inhibitory effect towards V.
One strain was able to inhibit E. Intrinsic antimicrobial activity of the LAB strains against several gastrointestinal pathogens. Zones of inhibition cm are shown. Microbial adherence to epithelial cells and inhibition of pathogen adherence : All the tested strains except Lactobacillus delbrueckii ssp.
Seven of the strains exhibited good adherence ranging from per cent when compared to the control E. Adherence intensity of the remaining strains varied from per cent compared to the control E. Most of the strains were able to inhibit the adherence of V. Vibrio adherence was inhibited almost completely by two strains - L. The remaining strains showed varying degrees of inhibition of Vibrio adherence, ranging from 20 to 60 per cent.
Most of the strains did not inhibit adherence of S. Adherence of LAB to Caco-2 cells. Inhibition of V. Typhimurium adherence to Caco-2 cells by LABisolated in this study. Experiments were done in duplicate.
Effects on cytokine secretion by cell lines : HT cells were exposed to the test strains prior to exposure to V. Curd fermented milk , freshly made by inoculation with starter curd, is a good source of bioavailable vitamin, minerals and folate 21 , and has less lactose and galactose than milk. Consumption of curd may enhance the immune response in the elderly.
These health benefits have been linked to the presence of live bacteria It is not hitherto known whether LAB present in home-made curd have the potential to confer health benefits. These included the ability to resist passage through the stomach in the presence of acid and pepsin, and the ability to grow in the proximal small intestine in the presence of pancreatin and bile salts.
Highly potent probiotic strains would have additional properties including antibiotic resistance, adhesion to intestinal epithelia, antimicrobial activity, inhibition of pathogen adhesion, and immunomodulation potential. Only one of the strains studied survived exposure to pepsin although several survived exposure to acid for varying periods of time.
However, it is unlikely that bacteria ingested in curd will be stressed to the extent as done in the present study, because the food with which curd is eaten is likely to buffer gastric acid and to limit pepsin effect. The p H in human stomach ranges from 1. These results are consistent with reports of ability of lactobacilli to retain their viability when exposed to p H values of 2. None of the lactobacilli survived in pepsin at p H 2.
Probiotic bacteria in curd will have the advantage of the presence of curd proteins which have a protective effect on the starters and support bacterial survival in the acidic environment of the stomach 23 , Even strains not able to survive at p H 1.
In contrast to pepsin, all the strains examined in this study survived in the presence of pancreatin or bile salts simulating the near neutral small intestine environment. The LAB strains exhibited resistance to a wide variety of antimicrobials. It is most likely that this reflects intrinsic resistance rather than genetic resistance which can be transferred to the specified antimicrobials, due to lack of targets in the microbes for these antimicrobials.
This property also makes them useful in combination with antibiotics, to prevent antibiotic-induced diarrhoea. Probiotic bacteria prevent the growth of pathogenic species by competing for nutrition and attachment sites on the colonic epithelium, and through production of organic acids and bacteriocins Several of the curd-derived LAB in this study inhibited growth of enteric pathogens.
This is a useful property, especially to prevent the development of food-borne illness in tropical warm climates. Inhibition was noted specifically against S. Typhimurium and V. Adherence of lactobacilli to the intestinal epithelium is considered to be essential for the exertion of a beneficial probiotic effect in the large intestine 27 , Most of the LAB tested in this study displayed adherence to Caco-2 cells, in numbers similar to that previously reported by others These LAB also inhibited pathogen adherence to Caco-2 cells.
Such inhibition of pathogen adherence to eukaryotic cell lines has been reported for strains such as L. The adhesion of V. Strains with higher adhesive ability might well occupy common adhesion sites and thus prevent the further adhesion of the pathogenic bacterium through a process of exclusion On the other hand, even a weakly binding Lactobacillus strain on a Caco-2 cell could stimulate cellular mechanisms immunomodulation , which may lead to increased colonization resistance or may interfere with pathogen adhesion to epithelium through mechanisms such as direct antagonism Further studies are required to elucidate the mechanisms underlying probiotic adherence and inhibition of pathogen adherence.
Epithelial cells are major constituents of the intestinal mucosal barrier and participate in innate immune and inflammatory responses in the gut. Modulation of interleukin-8 secretion by epithelial cell line HT is consistent with probiotic potential of the LAB tested.
Sub-epithelial cells, including monocytes, also participate in inflammatory responses in the bowel, secreting inflammatory products such as Th1 type cytokines, chemokines and several active oxides.
Expression of anti-inflammatory cytokines in the monocyte cell line THP-1 was upregulated by two of the LAB strains indicating the possibility of an anti-inflammatory effect.
This needs to be confirmed by further study. Lactobacilli are known to have anti-inflammatory effects in animal models of colitis It is likely that the daily ingestion of curd in certain cultures and communities confers health benefits beyond nutrient intake in curd.
A recent study using an animal model and parallel human studies showed that though long term consumption of fermented milk products did not change faecal microbiota composition, it significantly changed the expression of microbial enzymes involved in many metabolic pathways, particularly those related to carbohydrate fermentation In conclusion, the home-made curds that were evaluated possessed a spectrum of LAB that had the potential to exert probiotic effects in individuals consuming the curd.
These microbes had properties that predicted their ability to survive passage in the upper gut and to modulate gut mucosal innate immune reactions and, therefore, it is likely they have the potential to significantly influence health status.
Further studies should focus on the contribution of daily curd intake to health in India. Authors acknowledge the financial support received from the Department of Biotechnology, Government of India, New Delhi.
National Center for Biotechnology Information , U. Indian J Med Res. Balakrishnan S. Author information Article notes Copyright and License information Disclaimer.
Reprint requests : Dr B. Received Aug
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