Microbiology Chapter 14
Which of the following would be an example of disease transmission via INDIRECT contact?
A student sneezes on her test booklet. The instructor grades it and catches her cold.
Which of the following is an example of the symbiotic relationship known as mutualism?
E. coli within the large intestine
Malaria is an infectious disease caused by infection with a protozoan. In certain tropical regions, malaria is constantly present. We would say that malaria is a(n) _________ disease in these regions.
Endemic
Which of the following statements concerning pathology, infection, and disease is true?
Pathology refers to the study of structural and functional changes that occur in the body as a result of a disease.
Koch's Postulates: Understanding Disease
The concept that microorganisms can be linked to specific infectious diseases was largely unknown until recent history. During the Golden Age of Microbiology (1857 - 1914), scientists such as Louis Pasteur and Robert Koch significantly advanced the field of microbiology by studying the chemical activities of microorganisms, improving the techniques for culturing and viewing microorganisms, and developing vaccines and surgical techniques to prevent the spread of infection. They also identified the agents of many infectious diseases (those caused by microorganisms), thereby paving the way for more effective treatments. The concept of linking a microorganism with a specific infectious disease is known as the germ theory of disease. This theory was initially not widely accepted because, up until that point, disease was thought to be punishment for an individual's crimes or misdeeds. Most people did not believe that microorganisms could travel through the air or be transmitted on surfaces. Scientists ultimately laid these doubts to rest by accumulating the evidence needed to support the germ theory of disease. Early evidence that microorganisms caused infectious disease was obtained by Robert Koch, a German physician who, in 1876, discovered that rod-shaped bacteria (Bacillus anthracis) were responsible for causing anthrax in cattle. He developed a series of experimental steps, now known as Koch's postulates, to systematically link a specific microbe to a specific infectious disease. Koch found that certain bacteria (B. anthracis) were present in blood samples collected from cows infected with anthrax, and these bacteria were not present in healthy cows. Since the mere presence of bacteria was not sufficient proof that it caused disease, he took a blood sample from an infected cow and injected it into a healthy one; this second animal similarly developed anthrax. He repeated this procedure multiple times, and obtained the same results each time. He also grew bacteria isolated from infected animals on artificial media, and even after multiple culture transfers, this microorganism remained capable of causing anthrax in healthy animals. These experimental steps demonstrated that B. anthracis was the causative agent of anthrax. Since these early studies, such techniques have been key in determining the cause, or etiology, of many infectious diseases. An overview of the experimental approaches behind Koch's postulates is summarized in Foundation Figure 14.3. In summary, Koch's postulates state that: The same pathogen must be present in every case of the disease. (see steps 1 and 4) The pathogen must be isolated from the diseased host and grown in pure culture. (see step 2a and 5a) The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal. (see step 3) The pathogen must be isolated from the inoculated animal and must be shown to be the original organism. (see steps 2b and 5b)
Koch's postulates established criteria for proving that a specific organism causes a specific disease. Which of the following is NOT one of the criteria given by Koch's postulates?
The pathogen must be isolated from inoculated animals and must be different from the original organism.
Which of the following statements about the development of infectious diseases is correct?
The period of convalescence is the time during which the person regains health and fully recovers (back to the pre-disease state).
As a health care worker, I am keenly aware of how important it is to avoid harming my patients. I worry about inadvertently transmitting an infectious disease to an already compromised individual. According to the CDC, what is the MOST important thing I can do to avoid this?
Wash my hands before interacting with any patient.
A patient acquires an infection by touching a contaminated door handle. Which mode of transmission best describes this scenario?
indirect contact transmission
The following choices list several types of diseases, along with factors that may contribute to their emergence. Which disease and associated factor do NOT match?
emergence of avian influenza A (H5N1): use of antibiotics
Which of the following is a fungal zoonosis that can be transmitted by direct contact?
ringworm
Which of the following is classified as a latent disease?
shingles
Plague is transmitted through the bite of an infected flea. Which of the following best describes this mode of transmission?
vector transmission
A dog develops a diarrheal disease after drinking water from a creek during a hike with his owner. Which of the following best describes this method of disease transmission?
vehicle transmission
