- Assalamu alaikom, welcome again to another ATP video!
- Today’s we will continue our series on gram negative bacteria, and today we will take
about 3 clinically important curved rods, which are: Campylobacter jejuni, Vibrio cholerae, and
Helicobacter pylori. We will take in details about each one of them during this video, inshaAllah.
During the video, we will talk about the features of each organism, the clinical importance and the
treatment. As a start we want you to know that all these three organisms have two things in common in
addition to being curved rods, that is: they are oxidase positive, AND they are
flagellated organisms - The first organism we
will talk about is Campylobacter jejuni So for the important features for this
organism which can help you in identification are: 1- first feature, note that we will be
mentioning the same exact statement 3 times in today’s video which is:
gram negative, curved rod, oxidase positive with (POLAR) flagella
2- when you go camping what do you do? I know many things, but for the sake of this video
lets agree that you light fire ;) Likewise, Campylobacter grows at
relatively hot temp. at 42oC Now for clinical importance
It’s a common cause of bloody diarrhea, esp. in pediatric age group. Usually it can be transmitted
by one of three ways: 1- through person to person
2- contaminated/undercooked food or unpasteurized milk
3- or by touching infected animals It’s also associated with Guillain-Barré
syndrome (it’s an autoimmune disease affecting peripheral nerve [mainly schwann cells] and causes
ascending paralysis) and reactive arthritis Tx: for treatment we usually manage patients
with supportive care, i.e. by replacing fluids and electrolytes
However, antibiotic might be indicated if the patient is immunocompromised or
symptoms are not improving, in this case we can use azithromycin or erythromycin.
REMEMBER supportive therapy is usually the tx unless indicated otherwise
The second guest in our video is Vibrio cholerae. Again, we will talk about important lab features,
clinical importance and treatment. For its characteristic, remember the
common features between all 3 organisms? 1- Vibrio cholerae is a gram negative,
curved rod, oxidase positive with flagella 2- In addition, it grows in alkaline media
For clinical significance, It can be transmitted mainly by ingestion
of contaminated water or uncooked food. It’s sensitive to the high acidity in stomach; thus,
requires high dose to be able to infect humans. It can cause profuse watery diarrhea, and it
does that by secreting enterotoxin, how? The enterotoxin permanently activates Gs,
increase adenylyl cyclase activation > consequently leading to continues production
of cAMP. As a result, there will be increase in Cl- secretion, and H2O will follow > diarrhea.
Tx: again, it’s supportive, for that we use ORT (oral rehydration therapy)
Please note that there are other clinically important vibrio species such as:
- Vibrio parahaemolyticus: which can cause acute gastroenteritis
with diarrhea (can be watery or bloody) - And Vibrio vulnificus which can cause
septicemia, wound infection, or again gastroenteritis
The third and last organism we’re going to discuss is Helicobacter pylori.
Starting off with its features:
The first statement that we say issss: 1- Helicobacter pylori is a gram negative,
curved rod, oxidase positive with flagella 2- It’s also catalase + and urease + (sometimes
referred to as triple positive because of oxidase, urease, & catalase)
For clinical importance of Helicobacter pylori, it colonizes the antrum of the stomach.
It can cause peptic ulcer, that is in the stomach and/or duodenum (most common
cause of ulcer in each one separately, but the percentage is much higher in duodenal
ulcers). It also can cause gastritis. Now here we’ll go back to relate the
function of urease (the enzyme that H. pylori has in the pathogenesis). This enzyme breaks
down urea (in the presence of H2O) to CO2 and NH3 (ammonia). NH3 can neutralize the acidity
of the stomach, allowing H. pylori to survive. Moreover, the same enzyme helps in the diagnosis
of H. pylori, (active infection) by a test known as urea breath test.
Remember: Urea is broken down to NH3 and CO2, so the test works by giving the patient a
radioactive urea [in which the carbon atom is the radioactive component]. Once they take it,
if they have H. pylori in their stomach, it will be broken down to NH3 and radioactive CO2, and
then eventually they will exhale the radioactive CO2, and we can detect that, hurraaaay!!!
Helicobacter pylori is also associated with increased risk of gastric adenocarcinoma and
MALT (mucosa-associated lymphoid tissue) lymphoma. For the treatment of Helicobacter pylori, then we
have different combination, but the commonly used initial therapy is the triple therapy:
Amoxicillin or metronidazole if the patient is allergic to penicillin + Clarithromycin + Proton
pump inhibitor (PPI) Another treatment can be used
is quadruple therapy: tetracycline + bismuth + metronidazole + PPI
Remember these are not the only treatments which can be used to treat H. pylori
In summary, we talked about 3, gram negative, curved rods. The first two can cause diarrhea,
campylobacter usually bloody, while cholera is watery. The treatment of both is usually
supportive. The last one is helicobacter pylori, it commonly cases peptic ulcer disease,
and for that we can use triple therapy. Finally, we hope you enjoyed the video!
Let us know if you have any suggestion/feedback. And as always: don’t forget to like and subscribe
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