<prompt> Chacroid is caused by?N. GonnorreaH. DucreiT. PallidumH. Influenza  <response>: See APPENDIX-47 for list of STDs CHANCROID SOFT SORE This venereal infection is caused by the Gram-negative bacillus Haemophilus ducreyi.One to 5 days postinfection, a soft sloughy ulcer appears on the penis or vulva.The treatment of choice is erythromycin 500 mg 6-hourly for 14 days. 