Nonmotile among the Burkholderia is
**Core Concept**
Burkholderia species are a group of Gram-negative bacteria that can be motile or nonmotile, depending on the species. The motility of these bacteria is primarily determined by the presence or absence of polar flagella, which are essential for their movement. The ability to move or not move is a key characteristic used to differentiate between various species within the Burkholderia genus.
**Why the Correct Answer is Right**
The correct answer is based on the fact that Burkholderia pseudomallei, the causative agent of melioidosis, is nonmotile. This is because it lacks polar flagella, which are necessary for bacterial motility. The absence of flagella is a defining characteristic of B. pseudomallei, making it distinguishable from other Burkholderia species that are motile. The lack of motility in B. pseudomallei is also related to its ability to survive and thrive in environments with limited oxygen availability.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Burkholderia cepacia, a closely related species to B. pseudomallei, is motile. B. cepacia has polar flagella, which enable it to move and thrive in various environments.
**Option B:** This option is incorrect because Burkholderia mallei, the causative agent of glanders, is also nonmotile. However, it is a distinct species from B. pseudomallei and has a different set of characteristics.
**Option C:** This option is incorrect because Burkholderia thailandensis is motile. It has polar flagella, which allow it to move and thrive in various environments.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the nonmotility of B. pseudomallei is a key characteristic that distinguishes it from other Burkholderia species. This knowledge is critical for accurate identification and diagnosis of melioidosis, a serious disease that can be fatal if left untreated.
**Correct Answer: D. B. pseudomallei**