Vibrio Cholerae & Vibrio Vulnificus for the USMLE Step 1

Welcome to section 39 of bacteria. This is our bacteria overview figure. In this video, we'll be discussing Vibrio cholerae, which you can see right here. At the end of the video, we'll also introduce another species of Vibrio known as Vibrio vulnificus. This scene will take place outdoors as a group of friends are enjoying a fun camping trip together. The first two characters to the scene are sitting around a campfire telling each other scary stories. As you can see, the guy in the blue jacket has whipped out a flashlight and is shining the light on his popped collar as if he's acting like Dracula. Apparently, his cinematics and story have been successful because the guy in the orange jacket appears pretty frightened. Anyway, the prominent popped collar sounds like cholera and is here to help you remember that this image is all about Vibrio cholerae. Just like in our other images, notice that we've made the background pink, which is to help you remember that Vibrio cholerae is gram-negative. Next, notice that we've shown another character who has a prominent mustache. Just like in our Campylobacter video, the mustache is here to help you remember that Vibrio cholerae is a curved bacillus. Now you can see that we've shown a flag in the background. This is to help you remember that Vibrio is flagellated. This is a gram stain of Vibrio cholerae. Notice that it's pink or red, appearing curved and has prominent flagella, for example right here. So remember, Vibrio cholerae is a flagellated gram-negative curved bacillus. All right, the flag we showed a second ago is to help you remember that Vibrio is flagellated, but also notice that it has a picture of Africa on it. Some of these guys are from Africa, so they like to bring along flags from their home country when they go camping. Anyway, the African flag is here to help you remember that Vibrio cholerae is endemic to developing countries such as Africa. Now you can see that we've added another guy to the scene who appears to be preparing a lemon cobbler. Just like in our other videos, the lemons are here to help you remember that Vibrio is acid labile. This means that it's inactivated by the gastric acid in the stomach, so a large inoculum is required to cause infection. Next, notice that we've shown another guy towards the front of the image who was using a pump to fill up his mattress with air. If you've ever been camping, you've probably seen one of these before. Anyway, the pump is here to help you remember that proton pump inhibitors, or PPIs, increase the risk of infection. Hopefully, this is pretty intuitive. If an organism is normally inactivated by gastric acid, then a medication that reduces gastric acid, such as a PPI, will result in an increased risk of infection. Now we've added a girl to the scene who is wearing a blue necklace. Just like in our other videos, this is here to help you remember that Vibrio cholerae is oxidase positive. This is an image of the oxidase test, which we covered in more detail in section 20, which is our Neisseria overview video. Recall that if the organism is oxidase positive, then the disc will turn a blue or pink color, which is what we can see on the left right here. So remember, Vibrio is oxidase positive. All right, now we've shown one of the camper guys dumping his food into the water. Pretty inconsiderate, but I guess what can you do, right? Anyway, he's clearly contaminating the water with his food, so we've included this in the image to help you remember that Vibrio cholerae is transmitted via ingestion of contaminated water. Okay, now let's turn our attention back to the Dracula vampire guy. As you can see, there's something next to his feet. Let's zoom up so you can see this better. Ah, those are alkaline batteries that he used to power his flashlight to enhance the effects of his scary story. The word alkaline should help you remember that Vibrio cholerae is found in alkaline environments. Okay, now notice that we've shown two tents in the background. After all, these people are camping, so it makes sense that they brought tents along with them, right? Just like before, we've included the tents here to help you remember that Vibrio cholerae produces a toxin called cholera toxin that overactivates adenylate cyclase and increases levels of cyclic AMP. This, in turn, results in chloride secretion and water is pulled into the lumen of the intestinal tract, resulting in watery diarrhea. So people camping with tents for increased cyclic AMP. Remember the scared guy in the orange jacket? Well, you can see that he got so scared that he accidentally knocked over the pot of rice they were making for dinner. The rice is here to help you remember that Vibrio cholerae causes what's known as rice water diarrhea. This occurs because cholera toxin does not invade the intestinal mucosa. Rather, it induces mucus production of goblet cells and causes epithelial cells to slough off, giving the stool a rice appearance. Because the pathogen doesn't invade the intestinal mucosa, the pathogen doesn't produce intestinal damage, so no blood or inflammatory debris is present in the stool. This is an image of a stool sample from a patient with Vibrio cholerae. Notice that the stool is white and contains particles of mucus and epithelial cells, giving it the characteristic rice appearance. Understanding the pathophysiology here is pretty high yield, so remember the cholera toxin will cause a stool sample to contain mucus and epithelial cells. Okay, let's move on. We've also included a waterfall in the background to help you remember that Vibrio cholerae causes watery diarrhea, not bloody diarrhea. Finally, if we turn our attention back to the girl with the blue necklace, we can see that she's filling up a cup of water from a water jug. This will be our symbol for rehydration therapy, which is hopefully pretty intuitive. After all, she is in the act of rehydrating herself, so the water jug is here to help you remember that the treatment for Vibrio cholerae is oral rehydration solution. It's a self-limited condition that does not require antibiotics. Okay, now that we've covered Vibrio cholerae, let's move on to discuss Vibrio vulnificus. To represent this, we've shown a car with the prominent Volvo logo seen on the trunk, so Volvo car for Vibrio vulnificus. Next, notice that we've shown several snacks on the back of the trunk, including monkey animal crackers. By now, you should know that this is our symbol for lactose fermentation on MacConkey agar, so Vibrio vulnificus ferments lactose on MacConkey agar. This is a figure of MacConkey agar, and like we discussed in prior videos, the pink color right here indicates that the organism is a lactose fermenter. So Vibrio vulnificus would appear pink like this on MacConkey agar. All right, now notice that we've shown some oysters in the trunk. This is to help you remember that Vibrio vulnificus is associated with raw oyster consumption. Next, notice the pack of beer in the trunk. This is to help you remember that Vibrio vulnificus is associated with alcohol consumption. The owner of this Volvo is leaning against the car and enjoying some beer. You can also see that he just threw a beer to his friend with the mustache. Anyway, the guy sipping the beer is here to help you remember that Vibrio vulnificus can cause sepsis. Finally, notice that we've shown the car owner's dog right next to the trunk. He's a Dalmatian, so you can see that we've shown him with a liver spot, which is to help you remember that Vibrio vulnificus can cause liver damage. All right, now that we've covered the image, let's review with a question. A resident physician is working in Ghana on a humanitarian trip when a 19-year-old male presents to the clinic with a three-day history of watery diarrhea. He states that he recently drank some water that may have been contaminated. A stool sample reveals gram-negative oxidase-positive flagellated bacilli. The resident informs the medical team that his condition is caused by a toxin that A invades the gastrointestinal mucosa, B results in an absence of neutrophils in the stool, C sprea

will take place in the outdoors as a group of friends are enjoying a fun camping trip together the first two characters to the scene were sitting around a campfire telling each other scary stories as you can see the guy in

the blue jacket has whipped out a flashlight and is shining the light on his popped collar as if he's acting like dracula apparently his cinematics and story have been successful because the guy in the orange jacket appears pretty

frightened anyway the prominent popped collar sounds like cholera and is here to help you remember that this image is all about vibrio cholerae just like in our other images notice that we've made the background pink which is to help you

remember that vibrio cholerae is gram-negative next notice that we've shown another character who has a prominent mustache just like in our campylobacter video the mustache is here to help you remember that vibrio cholerae is a curved bacillus now you

can see that we've shown a flag in the background this is to help you remember that vibrio is flagellated this is a gram stain of vibrio cholerae notice that it's pink or red appearing curved and has prominent flagella for example

right here so remember vibrio cholerae is a flagellated gram-negative curved bacillus all right the flag we showed a second ago is to help you remember that vibrio is flagellated but also notice that it has a picture of africa on it

some of these guys are from africa so they like to bring along flags from their home country when they go camping anyway the african flag is here to help you remember that vibrio cholerae is endemic to developing countries such as

africa now you can see that we've added another guy to the scene who appears to be preparing a lemon cobbler just like in our other videos the lemons are here to help you remember that vibrio is acid labile this means that it's inactivated

by the gastric acid in the stomach so a large inoculum is required to cause infection next notice that we've shown another guy towards the front of the image who was using a pump to fill up his mattress with air if you've ever

been camping you've probably seen one of these before anyway the pump is here to help you remember that proton pump inhibitors or ppis increase the risk of infection hopefully this is pretty intuitive if an organism is normally inactivated by gastric acid then a

medication that reduces gastric acid such as a ppi will result in an increased risk of infection now we've added a girl to the scene who is wearing a blue necklace just like in our other videos this is here to help you remember

that vibrio cholerae is oxidase positive this is an image of the oxidase test which we covered in more detail in section 20 which is our niceria overview video recall that if the organism is oxidase positive then the disc will turn

a blue or pink color which is what we can see on the left right here so remember vibrio is oxidase positive all right now we've shown one of the camper guys dumping his food into the water pretty inconsiderate but i guess what

can you do right anyway he's clearly contaminating the water with his food so we've included this in the image to help you remember that vibrio cholerae is transmitted via ingestion of contaminated water okay now let's turn our attention back to the dracula

vampire guy as you can see there's something next to his feet let's zoom up so you can see this better ah those are alkaline batteries that he used to power his flashlight to enhance the effects of his scary story the word alkaline should

help you remember that vibrio cholerae is found in alkaline environments okay now notice that we've shown two tents in the background after all these people are camping so it makes sense that they brought tents along with them right just

like before we've included the tents here to help you remember that vibrio cholerae produces a toxin called cholera toxin that over activates adenylate cyclase and increases levels of cyclic amp this in turn results in chloride secretion and water is pulled into the

lumen of the intestinal tract resulting in watery diarrhea so people camping with tents for increased cyclic amp remember the scared guy in the orange jacket well you can see that he got so scared that he accidentally knocked over

the pot of rice they were making for dinner the rice is here to help you remember that vibrio cholerae causes what's known as rice water diarrhea this occurs because cholera toxin does not invade the intestinal mucosa rather it

induces mucus production of goblet cells and causes epithelial cells to slough off giving the stool a rice appearance because the pathogen doesn't invade the intestinal mucosa the pathogen doesn't produce intestinal damage so no blood or inflammatory debris is present in the

stool this is an image of a stool sample from a patient with vibrio cholerae notice that the stool is white and contains particles of mucus and epithelial cells giving it the characteristic rice appearance understanding the pathophysiology here is pretty high yield so remember the

cholera toxin will cause a stool sample to contain mucus and epithelial cells okay let's move on we've also included a waterfall in the background to help you remember that vibrio cholerae causes watery diarrhea not bloody diarrhea finally if we turn our attention back to

the girl with the blue necklace we can see that she's filling up a cup of water from a water jug this will be our symbol for rehydration therapy which is hopefully pretty intuitive after all she is in the act of rehydrating herself so

the water jug is here to help you remember that the treatment for vibrio cholerae is oral rehydration solution it's a self-limited condition that does not require antibiotics okay now that we've covered vibrio calorie let's move on to discuss vibrio vulnificus to

represent this we've shown a car with the prominent volvo logo seen on the trunk so volvo car for vibrio vulnificus next notice that we've shown several snacks on the back of the trunk including monkey animal crackers by now

you should know that this is our symbol for lactose fermentation on mcconkey agar so vibrio volnificus ferments lactose on mcconkey agar this is a figure of mcconkey agar and like we discussed in prior videos the pink color right here indicates that the organism

is a lactose fermenter so vibrio vulnificus would appear pink like this on mcconkey agar alright now notice that we've shown some oysters in the trunk this is to help you remember that vibrio vulnificus is associated with raw oyster

consumption next notice the pack of beer in the trunk this is to help you remember that vibrio vulnificus is associated with alcohol consumption the owner of this volvo is leaning against the car and enjoying some beer you can

also see that he just threw a beer to his friend with the mustache anyway the guy sipping the beer is here to help you remember that vibrio vulnificus can cause sepsis finally notice that we've shown the car owner's dog right next to

the trunk he's a dalmatian so you can see that we've shown him with a liver spot which is to help you remember that vibrio vulnificus can cause liver damage alright now that we've covered the image let's review with a question a resident

physician is working in ghana on a humanitarian trip when a 19 year old male presents to the clinic with a three-day history of watery diarrhea he states that he recently drank some water that may have been contaminated a stool

sample reveals gram-negative oxidase-positive flagellated bacilli the resident informs the medical team that his condition is caused by a toxin that a invades the gastrointestinal mucosa b results in an absence of neutrophils in the stool c spreads hematogenously to

vital organs or d increases levels of cyclic gmp okay there are a few key points from the question stem that should have helped you get the answer right first this scenario is occurring in ghana which is considered a

developing country second the patient has watery diarrhea third he drink contaminated water and fourth a stool sample revealed gram negative oxidase positive flagellated bacilli collectively these clues leave us with a diagnosis of vibrio cholerae so with this in mind the correct answer is b

results in an absence of neutrophils in the stool from the image recall that the guy knocking over the rice right here should help you remember that vibrio cholerae produces a toxin that results in rice water diarrhea as i mentioned earlier

the rice appearance that you can see in this image occurs because the toxin induces mucus production and causes the intestinal epithelial cells to slough off based on this you should have been able to deduce that the organism doesn't

produce intestinal damage or else blood and inflammatory debris would be present in the stool therefore the toxin is non-inflammatory and results in an absence of neutrophils in the stool so if we return to the question you can see

that a is incorrect because it doesn't invade the gi mucosa this is more typical of shigella or salmonella which cause bloody diarrhea so a is incorrect c is incorrect because this is describing salmonella which can disseminate hematogenously again

salmonella causes a bloody diarrhea so c is incorrect finally d is incorrect because vibrio cholera increases the levels of cyclic amp not cyclic gmp so again the correct answer is b results in an absence of neutrophils in the stool

and with that we've covered everything you need to know about vibrio cholerae and vibrio vulnificus