Clostridium difficile

Etymology
Clostridium difficile:

clostrid: "spindle" (from greek κλωστήρ (kloster), meaning "spindle")

difficile: "difficult" (from latin difficilis, meaning "difficult", which is from dis (not) facilis (easy))

Explanation
Clostridium difficilis is an anaerobic bacteria. It was classified into the genus Clostridium because of its anaerobic, spore-forming characteristics, and while rod-shaped, bacteria in genus Clostridium tend to be more spindle-shaped (clostrid) in general since they tend to have endospores (a thickened, toughened version of the bacteria that survives in bad conditions, which is part of what makes C difficile such a difficult bacteria to deal with). C difficile is very resistant to heat, and capable of surviving on many surfaces. This makes it really difficult (difficile) to eradicate in hospital environments, and it is a significant source of morbidity in such environments.