<s>[INST] context: Corynebacterium urealyticum (CU) (formerly Corynebacterium group D2) is a gram-positive bacillus with a strong urease activity that can infect the lower (acute or chronic cystitis) and upper (pyelonephritis and encrusted pyelitis) urinary tract. CU is a commensal skin organism that an estimated 12% of healthy individuals carry and it has been isolated in 30% of hospitalized patients. CU conves urea into ammonia, creating alkaline urine, which precipitates struvite and calcium phosphate crystals, forming stones and encrustations on the infected mucosa. Prolonged vesical and ureteral catheterization is considered the most impoant risk factor for developing encrusted cystitis (EC) and encrusted pyelitis (EP); these procedures not only carry CU or other urea-splitting micro-organisms into the urinary tract, but may also create conditions, e.g. urothelial trauma, that increase the risk of simple urinary tract infections turning into EC or EP . Bladder wall histology following resection of calcified encrustations reveals three distinct zones: a necrotic layer containing calcified encrustations revealed by Von Kossa stain; an inflammatory layer containing bacterial colonies, lymphocytes and polymorphonuclear cells; and normal tissue [/INST] question: Encrusted cystitis is caused by: | options: A: Corynebacterium xerosis B: Corynebacterium urealyticum C: Corynebacterium renale D: Corynebacterium pseudotuberculosis | answer: B </s>