The gut microflora or the probiotic organisms are the microorganisms inhabiting the digestive tract. There are more than 1000 species residing in various parts of the tract and most of them affect the host beneficially. Lactobacillus species form the predominant group amongst the probiotic organisms. Various sources like yogurt and cheese-whey were used to isolate Lactobacillus Acidophilus. When these were cultured, the most predominant organisms seen were Lactobacillus species and Yeast. Lactobacillus species were selectively isolated and screened further to isolate the Acidophilus. This culture was characterized and maintained in a medium specific to it. A comparative study of the growth kinetic parameters was made in a modified nutrient broth and in Rogosa media. It showed a remarkable difference in growth and was found to propagate profusely in the former media. The population of probiotic organisms in our digestive tract is highly susceptible to antibiotic intake and drug consumption. The extent of inhibitory effects of amoxicillin (ß-lactum), ciprofloxacin (fluoroquinolones) and the Minimum Inhibitory Concentration (MIC) of the two antibiotics were ascertained. Also, the effects of two commonly used Over- The-Counter (OTC) drugs namely a Paracetamol (acetaminophen: commercial name is Dolo-650) and a Non-Steroidal Anti-Inflammatory Drug (NSAID) (Ibuprofen: commercial name is Brufen) were studied. The effect on its viability was more stringent in the case of the antibiotics and in case of the OTC drugs, a minimal reduction in the viability of the culture was observed even at very high concentrations. However, at these concentrations, significant morphological variation was seen and these effects needed further investigation. Index Terms stability, macro-dilution, minimum inhibitory concentration MIC, over-the-counter OTC, susceptibility and tolerance, specific growth, doubling time.

Key words:Antimicrobial Agent, Plant extract, Clinical specimen, Minimum Inhibitory Concentration (MIC)