Campylobacter jejuni is one of the most common bacteria that causes gastroenteritis in humans. Its infection is fatal among young children, elderly, and immunosuppressed individuals. In line with this, we need to know what kind of method is used to detect this bacteria.
Campylobacter jejuni is a microaerophilic and fastidious bacterium needs a lot of effort for isolation and identification. Actually, I worked on this bacterium in my Ph.D. project, and I follow the standard protocols of ISO and OIE, 2016. In these protocols after processing samples we used several media and broths for isolation and presumptive identification of this bacterium, then used a diagnostic kit for identification. Confirmation of this bacterium at species level was then done using PCR to detect the Hip O gene in this bacterium.
Identification of Campylobacters on/in different mediums.
Medium
Morphology,color of Campylobacters colonies on/in different agar and broth.
A- Agar
Typical colony appearance :
Translucent moist colonies
1-Blood agar
2-Preston agar
Typical colony appearance :
round to irregular with smooth edges. They may have translucent, white growth to spreading, film like transparent growth. Some strains appear tan or slightly pink.
3- Preston agar without supplement
Typical colony appearance:
round to irregular with smooth edges. They may have translucent, white growth to spreading, film like transparent growth.
B - Biochemicals
a . Motility (wet mount slide).
spiral or curved slender rods with a corkscrew-like motility.
1- Microscopic examination
b . Morphology (Traditional Gram stain)
G-ve curved rode , When two or more bacterial cells are grouped together, they form an “S” or a “V” shape of gullwing.
2- Oxidase test
A positive test was indicated by the production of a dark purple colour within 5 – 10 seconds.
3- Catalase Test
A positive test was indicated by the formation of an bubbles within 30 seconds.
4- H2S production in Triple Sugar Iron medium
A positive reaction: A black precipitate in butt indicates H2S production (C.coli), Negative reaction: No black precipitate in butt indicates H2S doesn’t produce (C.jejuni).
5- Hydrolysis of Sod. hippurate
Slowly adding 200 μl 3.5% ninhydrin solution:
Positive reaction: dark purple/blue (C.jejuni) , negative reaction: clear or grey (C.coli).
6- O.B.I.S. Campy
a . Gram-lysis Test
A positive result: viscous appearance to the mixture and the presence of the DNA string. This indicates that the organism is Gram-negative (Campylobacter spp.).
b . L- ALA Test
A positive reaction: appearance of a dark purple colour around the original colony material within 20 seconds (not Campylobacter spp. ) , negative reaction (Campylobacter spp.).
Please see the following RG links:
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Article Prevalence of Campylobacter jejuni In Chicken Meat Marketed ...
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