1. Why do Coxiella show variable Gram stain results-that is, why would they stai
ID: 6571 • Letter: 1
Question
1. Why do Coxiella show variable Gram stain results-that is, why would they stain gram-positive or gram-negative at different times? Tell which stage is G + and which stage is G-, Also, explain if Coxiella should be classified as gram-positive or gram-negative when classified?2. What disease does C. burnetii cause? Why can this disease be transmitted by airborne routes while other (closely related) rickettsia species require insects and ticks for transmission to humans? Give an example of a closely related rickettsia species to Coxiella burnetii and tell how it is transmitted.
Explanation / Answer
1).Coxiella burnetii displays a prototypic gram negative cell wall structure when observed by an transmission electron microscope.
Giemsa staining is mostly used for these organisms. They show highly pleomorphic coccobacilli.
Coxiella have diphasic developmental phases and constitute spores in their life cycle.
The gram variable nature of Coxiella is due to the pleomorphic nature of it.
It can create pseudo-spores which constitute different wall chemistry resembling the gram positive nature. They can hold the iodine/crystal violet mordant similar to peptidoglycan in Gram (+) bacteria.
General Coxiella shows G- nature.
Spore stage of organism exhibits the G+ nature.
During classification the organism can be classified under the gram negative category.
2). Disease caused by Coxiella burnetii is Q (query) fever. Human being can be infected with a single bacterium. It infects cattle, goats and sheep.
These organisms are resistant to heat, drying, and many common disinfectants. These features enable the bacteria to survive for long periods in the environment. Infection of humans usually occurs by inhalation of these organisms from air that contains airborne barnyard dust contaminated by dried placental material, birth fluids, and excreta of infected herd animals.
Examples of a closely related rickettsia species to Coxiella burnetii that cause diseases are
Rickettsia rickettsii causes rocky mountain spotted fever transmits by ticks.
Rickettsia typhii causes murine typhus and transmits through ticks.
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