Final answer:
The likely diagnosis for a painful genital ulcer with tender suppurative inguinal adenopathy is chancroid, caused by the bacterium Haemophilus ducreyi.
Step-by-step explanation:
The combination of a painful genital ulcer and tender suppurative inguinal adenopathy suggests the diagnosis of chancroid.
This sexually transmitted infection is caused by the gram-negative rod Haemophilus ducreyi.
Unlike the hard chancres of syphilis, chancroid is characterized by soft chancres, which are painful, open sores that can bleed or produce a highly contagious fluid. Moreover, this infection can invade the lymph nodes, leading to inguinal adenopathy where the lymph nodes can become swollen, tender, and may discharge pus through the skin.