John works as lab technician in a diagnostic laboratory. In a field incidence of
ID: 143257 • Letter: J
Question
John works as lab technician in a diagnostic laboratory. In a field incidence of anthrax outbreak, he collected blood sample from sick cattle for isolation of Bacillus anthracis, the causative agent of anthrax, a fatal zoonotic disease. After having inoculated the blood sample in an appropriate media and incubated at 37°C, he totally forgot to take out the culture media from incubator for over a month. Explain what would possibly happen to the bacteria. What do you expect to see under a microscope if you do appropriate staining of colonies from such culture? What public health importance does this phenomenon have?Explanation / Answer
Explain what would possibly happen to the bacteria?
B. anthracis is a Gram-positive, aerobic or facultatively anaerobic, endospore-forming, rod-shaped bacterium. After more than 20–24 hours of incubation, the nutrients in the culture media will get depleted and the vegetative cells started forming spores (polypeptide capsule) at the end of the log phase of multiplication.
What do you expect to see under a microscope if you do appropriate staining of colonies from such culture?
In Gram-stained preparations, the developing spores appear as unstained areas within the cell. With malachite green/safranin (or malachite green/basic fuchsin) staining, the spores and vegetative forms are stained green and pink, respectively. In the Ziehl–Neelsen staining, the spores and vegetative forms are stained pink and blue, respectively. When fully mature (dormant), the spores can also be seen as refractile egg-shaped bodies under phase contrast microscope.
What public health importance does this phenomenon have?
The spore-forming phenomenon of the B. anthracis has serious effect on the public health, which allows the bacterium to be resistant to heat, freezing, chemicals, and other adverse environment conditions. This might lead to serious outbreak of anthrax infection among the livestock or humans.
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