With Campylobacter jejuni, “campylo” means curved, “bacter” means rod, while “jejuni” refers to the jejunum, which is a segment of the small intestines found between the duodenum and the ileum.
So, Campylobacter jejuni is a comma-shaped bacteria, and it’s one of the most common causes of bacterial gastroenteritis worldwide.
It's commonly found in foods like poultry, and unpasteurized milk.
Now, let’s talk microbe anatomy and physiology. Campylobacter jejuni is a comma-shaped bacteria that has a thin peptidoglycan cell wall, which doesn’t take in the purple dye when Gram stained, and instead appears pink or red – which makes it a gram-negative bacteria.
It also has a flagellum at one end which it uses to get around, so it’s a motile bacteria.
In addition to this, it’s oxidase-positive, meaning that it can use oxygen to create stored energy or ATP.
Lastly, Campylobacter jejuni is a microaerophile that loves warmth, so it grows best in low-oxygen environments, at 42 degrees Celsius, on blood agar varieties like Skirrow, Butzler, and Campy-BAP.
Alright, Campylobacter jejuni is usually transmitted from animals to humans, via the fecal-oral route.
In other words, you catch it by ingesting stool particles containing the bacteria.
Campylobacter jejuni usually resides in the gastrointestinal tract of birds.
So, when people eat raw and undercooked poultry, there's a possibility of infection.
Similarly, cows are common carriers, so people that drink unpasteurized milk can also risk infection.
There’s also direct contact with infected pets, notably puppies which excrete the bacteria in their stool.
Kids are the most susceptible to getting infected after playing with an infected pet.
Lastly, infected stool can end up in sources of freshwater, like rivers, and cause infection.
Once inside our body, Campylobacter jejuni has a number of virulence factors that it can use to attach to host cells and cause disease.
First, it has fimbriae-like filaments and cell surface proteins like PEB1 and CadF that help it attach to the mucosa of the small intestine and colon.
There, Campylobacter jejuni uses its spiral shape and long flagella to ‘drill' into the mucosa where they release toxins called cytolethal distending toxins.
These toxins damage nearby intestinal epithelium cells, further worsening the inflammation.
When the inflammation and damage becomes pretty extensive the colon might dilate, resulting in toxic megacolon.