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.