Acid Lakes and Fermenting Bogs The stomach is an organ of mass destruction for microbes They are churned and tumbled in a highly acidic environment few microbes can survive All that acid keeps many disease producing microbes in food and water from launching a successful invasion on the small or large intestine Peptic Ulcers Symptoms and prognosis Symptoms Burning sensations located between the breastbone and belly button Vomiting blood Chronic ulceration of the stomach has been indicated to lead to primary cancers of the stomach Helicobacter pylori A spiral shaped bacterium was found associated with severe stomach illness in cat Could it be cause d by human peptic ulcers How do you determine without a doubt if a specific microbe causes a specific disease Koch s Postulates An experimental algorithm developed by a 19th century German physicianresearchers Robert Koch One of the first Nobel Prizes in Medicine 1905 was awarded to Koch for the advances in preventing infectious diseases that derived from applying his postulates Koch s Postulates 1 The suspected agent must be present in every case of the disease 2 The suspected agent must be isolated from the diseased host and obtained in pure culture 3 The purified suspected agent must cause the disease when inoculated into healthy susceptible hosts 4 The suspected agent must be re isolated from the infected host and shown to be the same organism Koch applied his postulates using a disease of animals and humans Result Anthrax caused by the bacterium Bacillus anthracis A guinea pig s tale Barry Marshall an Australian M D performed Koch s postulate s on an unusual subject himself Unable to develop a convincing animal model Marshall s boss Dr J R Warren assisted him in performing Koch s 3rd postulate for stomach ulcer disease Within two weeks after drinking a culture of Helicobacter pylori the previously healthy Dr Marshall was diagnosed as suffering from severe gastric inflammation Then H pylori were re isolated from his inflamed stomach lining Outcome Warren and Marshall won the 2005 Nobel Prize in Medicine Stomach ulcers are now non existent in the developed world Grinder and Absorber Once in the small intestine microbe must withstand detergent like bile salts made in the liver and designed to tear microbes apart The large intestine or sigmoid colon is a metropolis of microbial life containing at least 5 600 different species of normal flora They supply us with vitamin K vitamin B12 thiamin and riboflavin These gut microbes maintain an intensely competitive and closed community which makes invasion from diseaseproducing microbes a considerable challenge The inside of the small intestine is covered with tiny microvilli that expand the surface area of the gut to approximately 200 square feet the size of a singles tennis court This large surface area optimizes digestion and absorption As important as the microbes in the gut are most don t appreciate them particularly those microbes that produce gases as part of the metabolism hydrogen carbon dioxide methane and odorous sulfur containing gases Antibiotics have saved many lives over the last 50 years but most aren t specific or selective in the kind of microbes they kill Often normal gut flora is destroyed by antibiotics taken to treat infections in other parts of the body This changes the balance of microbes in the gut The Balance Shifts An imbalance in normal intestinal flora often results in pseudomembranous colitis an infection by bacterial gut opportunist Clostridium difficile Symptoms chronic diarrhea following a course of antibiotic therapy In the United States it causes roughly three million cases of diarrhea and colitis annually It is also one of the most common hospital acquired intestinal infections in the U S Probiotics restoring gut balance Many companies are now marketing products to restore microbial balance in the digestive tract and generally improve health Overview The stomach has the lowest number of microbes in the human digestive tract For many years peptic ulcers were thought to be caused by stress and poor diet In the 1890s Robert Koch MD developed a set of postulates that clearly demonstrate if a specific microbe causes a specific disease Koch was awarded a Nobel Prize in 1905 for applying his postulates to find the cause of tuberculosis Drs Barry Marshall and J R Warren performed Koch s postulates on Dr Marshall and demonstrated that Helicobacter pylori could cause stomach ulcers The normal human gut contains 5 600 different kinds of microbes that help digest food and generate important vitamins for human health Oral antibiotic use can disrupt normal gut flora resulting in pseudomembranous colitis caused by C difficile Commercial probiotics help restore normal gut flora