here is a sample answer for the question. but i dont have the stimulus for it.
to identify whether a particular organism is the cause of an infectious disease Koch's postulates are often used:
step 1: causative organism will be present in all animals suffering the disease and absent in healthy animals.
step 2: the causative organism must be isolated from the host and grown in pure culture.
step 3: a healthy host infected with the pure culture must have the same symptoms are the original host.
step 4: the suspect organism must be isolated from the secong host, grow in pure culture and proven to be identical to the first culture.
step 1 appears to have only been partially fulfilled, as there is no mention of other healthy people being checked apart from marshall, and the data provided does not confirm that they found H pylori in every patient. if marshall was able to swallow a dose of H pylori, the step 2 must be carried out. marshall only developed symptoms of gastritis and not stomach ulcers, so step 3 was only partially satisfied. there is no mention as to whether the scientists re-isolated the bacteriul from marshall and compared it to the original bacterial culture, so it would appear that step 4 was omitted. hence koch's postulates were only partially fulfilled.
the use of several different technologies, eg. microscopic study, endoscopy, and staining techniques, as well as variety of methods to provide several different approaches to their research is commendable. however, the use of marshall in this experiment raises ethical concerns - especially as other humans are not likely to want to subject themselves to swallowing H pyroli.
the use of the words 'patients' suggest more than one patient was examined, however, it is not certain how many patients with the disease were examined and if there was a large enough sample size of both affected and unaffected people for repitition of the results, so the procedures appear to lack reliability. there is no mention of a control or the use of controlled variables, so their procedures lack validity.
their conclusion is not sufficiently supported by the experimental evidence described here, as marshall only developed gastritis and not a stomach ulcer, and so it cannot be said conclusively that H pylori causes stomach ulcers and gastritis.
