Chancroid: Definition and Pathology

00:01 We now turn our attention to another sexually transmitted infection known as chancroid, and I want you to think about that word for a second.

00:11 Chancroid means “like chancre”.

00:20 Chancroid is a sexually transmitted infection, which is characterized by an ulcer, kind of like syphilis, but inguinal lymphadenitis, and this infection is caused by a microorganism known as Haemophilus ducreyi.

00:43 It’s a pretty rare infection, at least rarely recognized in the United States.

00:48 It’s got a prevalence of about 8 cases in the US in 2011, so you can see it’s not really common.

01:00 The transmission is primarily heterosexual – affects males more than females.

01:06 And one risk factor that seems to be important is contact with commercial sex workers and there is a strong association with drug use.

01:17 A little bit about the organism, Haemophilus ducreyi, it seems to be a strictly human pathogen and it’s highly fastidious, which means it’s difficult to grow, it has special growth requirements.

01:35 It requires exogenous heme to survive.

01:40 And so, we’re going to be using chocolate agar much like we used it for Neisseria gonorrhoeae.

01:48 We’re not going to be using Thayer-Martin media, however.

01:54 On gram stain, it has a distinctive appearance.

01:59 What we have are rather pleomorphic bacilli that tend to clump-in together, as in a school of fish.

02:11 I think you can see this representation reminds you of a school of fish.

02:23 It is transmitted from person-to-person by intimate contact – genital-genital, oral-genital.

02:32 It directly penetrates the mucous membranes via some kind of abrasion or fissure in the skin.

02:42 From there, it will progress from a tiny papule to a pustule, to an ulcer.

02:53 It seems to associate itself with neutrophils and macrophages, but it’s not easily phagocytosed by them.

03:03 The ulcers pathologically contain predominantly T-cells with low numbers of B-cells.

03:10 It turns out in chancroid that repeated infections are possible.

03:15 There’s no life-long immunity, and that indicates that natural infection does not lead to protective immunity, and that may reflect the low numbers of B-cells that we find in lesions.