Limitations would be;
Replication, conditions (i.e. where the ambient conditions the same, temp, sunlight, humidity, etc)
Stolen from HSC Online
describe the contribution of Pasteur and Koch to our understanding of infectious diseases
Louis Pasteur
The role of Pasteur in identifying the causes of disease was:
that he disproved the theory of spontaneous generation, which was widely held at the time. Before Pasteur's work, people believed that maggots and fungi grew naturally from non-living material
that he showed that micro-organisms came from pre-existing micro-organisms.
Louis Pasteur (1822-1895) National Health Museum, USA
Robert Koch
About 150 years ago, Pasteur's work in identifying, under the microscope, the organism that caused fermentation, led some people to suggest the infectious diseases were caused by microscopic pathogens. Others argued that bacteria found in sick animals followed the infection, rather than causing it.
The work of Robert Koch (1843 - 1910) provided the proof that was needed to convince people that microscopic pathogens cause disease. His first experiments were with the disease anthrax in sheep. Later, he obtained similar results for tuberculosis and cholera.
First Koch found bacteria in sheep infected with anthrax. Then, he placed the bacteria on agar plates in Petri dishes so that many colonies of the bacteria were produced. He used bacteria from these colonies to infect healthy sheep and found that they became infected.
After his experiments with anthrax, Koch was able to state a series of steps that are needed to identify the micro-organism responsible for a particular disease. These steps are called Koch's postulates.
Step 1: All infected hosts must contain the suspect organism.
Step 2: A pure culture of the suspect organism must be obtained.
Step 3: A healthy organism infected with the pure culture must have the same symptoms as the original host.
Step 4: The suspect organism must be isolated from the second host, grown in pure culture and prove to be identical to the first culture.
Koch's postulates can be used to identify the causative organism of an infectious disease. The symptoms of the disease are carefully identified and then the blood of sufferers is examined to determine possible causative organisms. A particular micro-organism will be suspected if other sufferers have the same micro-organism present in their blood and a mechanism can be identified to allow transfer of the micro-organism. Identification of the organism in more sufferers will confirm the causative organism. Sometimes, a suspected causative organism can be confirmed by infecting a test organism.