Campylobacter jejuni is one of the bacteria that cause diarrhea. Others include Salmonella, Shigella, Vibrio cholerae and pathogenic Escherichia coli. Laboratory diagnosis of campylobacter jejuni or other species of campylobacter is not complicated especially in a good laboratory.
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Clinical Presentation of campylobacter infection.
Doctors begin to suspect campylobacter infections on some clinical background, which includes diarrhea (often watery or bloody), abdominal cramps, fever, nausea, and vomiting. This Symptoms typically last 2–10 days; severe cases can lead to dehydration or complications like Guillain-Barré syndrome. Those who are at risk of this bacteria infection are young children, the elderly, and immunocompromised individuals who may experience more severe symptoms.
When this suspicion of infection is established, the next step is to send the patient’s stool or feces sample to a medical laboratory for diagnosis. The complexity of a laboratory determines the diagnostics tools available for use.
Different Testing Methods for Campylobacter jejuni Diagnosis in a Lab.
They are
- Culture
- Gram stain
- PCR
Stool Culture for Campylobacter jejuni.
Two common culture media that are used to culture stool for campylobacter species are
Blood agar and
CCDA (Charcoal Cefoperazone Deoxycholate Agar).
CCDA (Charcoal Cefoperazone Deoxycholate Agar)
CCDA is commonly used in microbiology labs for isolating Campylobacter, especially Campylobacter jejuni and Campylobacter coli, which are frequent causes of bacterial diarrhea. This is the primary media for selective isolation of campylobacter.
When the stool is cultured on the CCDA, it is incubated at 42 degrees Celsius , and in a microaerophilic environment (reduced oxygen, increased CO₂). The incubation period is 24 to 48 hours but its better left for a complete 48 hours incubation period before examining the plates.
How Campylobacter jejuni Colonies Look Like on CCDA After 24-48 hours Culture.
Size and Shape: Colonies are typically small (1-2 mm in diameter) and round.
Color: They appear as grayish or translucent colonies with a slightly shiny or moist texture.
Texture: Colonies can have a smooth or slightly mucoid surface
Below is campylobacter jejuni on both blood agar and CCDA.
With this growth on CCDA, the suspicion of of campylobacter species or jejuni is high and the next step is to do Gram stain
Campylobacter Gram Stain.
On a Gram stain, campylobacter jejuni are Gram Negative bacilli and curved. It looks like the wing of a gull popularly described as ‘gull-wing appearance‘.
Gram stain in this case is diagnostic. Most labs that do not have molecular testing platforms would end here.
Below is how Campylobacter looks like on a Gram Stain
Compare this with normal Gram Negative bacteria like E coli
The other method for campylobacter diagnosis is :
Campylobacter PCR Test
This is molecular testing which determines Campylobacter genes. There are many PCR platforms which can detect Campylobacter genes. This testing method may be common in developed countries but not so in developing countries. PCR testing is quick and sensitive.
Before I conclude, I would like to explain the components of CCDA that makes it selective for Campylobacter isolation
CCDA Components and Function
Charcoal: Helps neutralize toxic byproducts that might inhibit Campylobacter growth.
Cefoperazone: An antibiotic that suppresses the growth of other bacteria, allowing selective growth of Campylobacter.
Deoxycholate: A bile salt that also helps inhibit non-target bacteria, enhancing the selectivity of the medium.
Agar :Creates a solid surface on which Campylobacter colonies can grow, making it easier to isolate and identify individual colonies
