Ever had a dodgy chicken sandwich that left your stomach in knots? Or heard of someone feeling numbness after a bout of food poisoning? It might have been down to a little mischief-maker called 'Campylobacter'. In this post, we'll dive into what this bacterium is all about, why it loves to hide in chicken, and some of its peculiar habits like thriving in warm environments and being a bit shy around oxygen. Plus, we'll discuss a mysterious condition called 'Guillain-Barré Syndrome' that might follow this food poisoning – a syndrome where your body's own defense system goes a bit rogue. And, of course, we'll give you some top tips to keep these unwanted dinner guests away from your plate. Ready to become a food safety expert? Let's dive in!
Understanding Campylobacter: A Domino Effect from its Habitat
Before we delve into this cascade of knowledge, it would be helpful to first read through a basic article on Gram staining and microbial characteristics available on our blog. This foundational reading will pave the way for the smooth flow of understanding that follows, akin to a well-aligned domino fall.
1. Habitat of Campylobacter: This bacterium mainly lives in the intestines of birds, where there's plenty of moisture.
2. Type of Bacterium: Because of its habitat, we know that Campylobacter is a Gram-negative bacterium.
3. Nature of Infection: Being Gram-negative, it's a type of bacterium that causes infectious food poisoning.
4. Unique Growth Temperature: What makes Campylobacter stand out is its optimal growth temperature, which is high at 42°C, and it can't grow below 30°C.
5. Physical Vulnerabilities: Just like other Gram-negative bacteria, Campylobacter is sensitive to dry conditions and extreme heat.
6. Oxygen Requirement: Most bacteria can be categorized based on their oxygen needs: those that need oxygen (aerobic), those that can grow with or without oxygen (facultative anaerobic), and those that can only grow without oxygen (obligate anaerobic). Campylobacter, however, doesn't fit neatly into any of these groups. It can't grow in regular air (with 20% oxygen), nor can it grow in complete absence of oxygen. Instead, it thrives in conditions with moderate oxygen levels, between 3% and 15%. This characteristic is termed "microaerophilic". Unlike other bacteria that can switch their metabolism based on oxygen presence, microaerophilic bacteria like Campylobacter need certain oxygen levels to sustain their metabolism.
This characteristic sets them apart from another group known as "facultative anaerobes". These bacteria are quite adaptable! Depending on the oxygen availability, they can switch between fermentation and another process known as the citric acid cycle. It's like having a dual power source.
On the other hand, microaerophiles have a more straightforward approach. They primarily depend on the citric acid cycle for their energy. But there's an interesting twist! While they rely on this oxygen-dependent process, they're sensitive to high oxygen levels in the air. It's like they need just the right amount of oxygen to thrive, but too much becomes a problem for them.
Think of them as those friends who love a bit of sunshine but can easily get sunburned. While they generally like oxygen, too much of it can harm them.
For a clear explanation on the difference between anaerobic and aerobic bacteria, see the article below for more information.
Understanding Gram-Negative Bacteria: The Role of the OF Test
7. Grow during distribution of Chicken? Given that its minimum growth temperature is 30°C, Campylobacter doesn't proliferate in standard storage temperatures for chicken or its processed products. So, concepts like adjusting pH or using preservatives to control its growth in food aren't applicable.
8. Growing Campylobacter in Labs: Being a Gram-negative bacterium, we can use certain compounds in a selective medium to promote Campylobacter's growth while suppressing the growth of Gram-positive bacteria.
By understanding these points sequentially, much like toppling dominos, we can better grasp the nature of Campylobacter and its implications in food safety.
The Spiral Shape of Campylobacter
Bacteria come in various shapes, but two common ones you might have heard of are spherical (coccus) and rod-shaped (bacillus). But today, let's talk about a unique one - the spiral or helical shape.
Unlike many other bacteria, Campylobacter doesn't fit into the categories of coccus or bacillus. Instead, it sports a distinctive spiral shape. Now, there aren't many bacteria out there with this corkscrew-like form. One of its famous spiral-shaped cousins is Helicobacter pylori, which is known for causing stomach ulcers.
Interestingly, there was a time when scientists believed that Helicobacter pylori was a type of Campylobacter. However, with advancements in molecular biology, specifically the analysis of 16S ribosomal DNA, they discovered that the two are actually distinct and belong to different genera. Quite a plot twist in the world of microbiology!
The Natural Home for Campylobacter
It's believed that the primary natural hosts for the bacteria Campylobacter are birds. Let's delve into why:
１．Widespread Presence in Birds: Campylobacter can be found in the gastrointestinal tracts of many different bird species in the wild. Sure, we sometimes find it in pigs and cows too, but here's the thing: when birds carry Campylobacter, they don't show any symptoms. They're totally chill! On the other hand, in pigs and cows, the bacteria might cause some serious problems like miscarriages or dysentery.
２．The Temperature Connection: Campylobacter thrives at a toasty 40-42°C. Coincidentally, this temperature aligns with a bird's body temperature. Think about birds for a moment. If they can't swiftly take off from the ground and soar into the sky, they're in danger. So, they essentially have to keep their "bodily engines" idling at all times, maintaining this high body temperature. Also, when a creature as small as a bird flies, the relationship between its surface area and volume means it loses heat rapidly. This means birds need to have their body temperatures set about 5°C higher than mammals.
Given these reasons, it's no surprise that the optimal temperature for Campylobacter matches the body temperature of birds. So, looking at all the evidence, it's reasonable to say birds are the natural hosts for Campylobacter. Cool, right?
The Culprit Behind Campylobacter Gastroenteritis: Chicken Meat
When we talk about the food most often linked to Campylobacter gastroenteritis, we're essentially talking about chicken. Now, we typically don't munch on raw chicken, right? So, most cases of Campylobacter food poisoning arise from undercooked dishes like fried chicken. But it's not just about the cooking! Picture this: you buy raw chicken, chop it up with a knife, and that same knife contaminates another dish with Campylobacter - another common way to get food poisoning.
Interestingly, in Japan, some folks do enjoy eating raw chicken, which annually turns out to be a primary cause of Campylobacter food poisoning there.
By the way, unlike bacteria like Salmonella, once Campylobacter is transferred, let's say from a knife, it doesn't multiply in the contaminated food. Why? Because it needs a minimum temperature of 30°C to grow.
Here's a twist though: Campylobacter, being genetically close to the stomach-loving Helicobacter pylori, can withstand the acidity of stomach acid. So, it doesn't take much for it to infect us. Believe it or not, just a single drop of chicken juice containing around 500 bacterial cells can do the trick.
This means that secondary contamination from tools like knives can lead to food poisoning, even with a small number of bacterial cells. So, worldwide, it's not just about eating raw or undercooked chicken. Cross-contamination plays a big role too. Despite the differences in how people in Japan and elsewhere might get Campylobacter gastroenteritis, the common denominator is always the Campylobacter present on chicken. Quite a sneaky little bugger, isn't it?
Why It Takes So Long to Get Sick from Campylobacter
One of the tricky things about Campylobacter gastroenteritis is that it takes longer to show up than other foodborne illnesses. Picture this: If you eat something contaminated with Salmonella or E. coli, which causes bloody diarrhea, you'd typically start feeling sick within about 24 hours. But with Campylobacter? It's a bit more sneaky. You might not feel off for 2 to 7 days after you've eaten the bad stuff.
Why is this? Well, bacteria like Salmonella and E. coli double their numbers pretty quickly. It takes them only 20 to 30 minutes to divide and multiply at our body's temperature. But Campylobacter? It's like the sloth of the bacteria world. At 37°C, it needs a whole hour just to split into two. And if you drop the temperature below 30°C, it can't divide at all.
Because Campylobacter needs higher temperatures to grow and takes its sweet time multiplying, it's why we have to wait longer to see if we've won the food poisoning lottery with this bug. Not the kind of prize anyone wants to win, right?
Why Campylobacter Might Be Sneakier Than You Think
When Campylobacter bacteria infect the cells lining our intestines, they disrupt the normal absorption and secretion processes. This leads to an increased release of fluid, resulting in the all-too-familiar symptom: diarrhoea.
However, the initial symptoms of Campylobacter poisoning aren't that bad. In fact, most people recover within 2 to 5 days.
But here's the twist: about 10 days after recovering, 1 in 1,000 people will develop something called Guillain-Barré Syndrome. Sounds fancy, but trust me, it's not something you'd want. It causes the nerves in our arms and legs to become paralyzed. Moving, walking, even breathing can become challenging in severe cases.
Now you might be wondering, why does this happen after Campylobacter poisoning? It's believed that Guillain-Barré Syndrome is triggered when our immune cells, which should be defending us, mistakenly attack our own nerve cells.
Why would our own body turn against us?
Well, the structure of certain sugars (polysaccharides) on our nerve cells looks suspiciously like those found on the outer layer of Campylobacter. So, when we get infected, our immune system gears up to fight off Campylobacter by targeting these sugars. And while they're pretty good at beating the bacteria, some of these overeager immune cells stick around after the battle. With Campylobacter gone, they might mistake our own cells, which have similar-looking sugars, as the enemy. This misidentification can lead to Guillain-Barré Syndrome.
It's fascinating how something so small can have such a ripple effect in our bodies, isn't it?
Guillain-Barré Syndrome: Not Just After Food Poisoning, But COVID-19 Too?
Remember that Guillain-Barré Syndrome (GBS) I mentioned earlier? The one that can paralyze our arms and legs after Campylobacter poisoning? Well, it's not just caused by food poisoning. Various infections can trigger it. In fact, while Campylobacter is the most commonly reported precursor to GBS, other infections, including the flu, have also been linked to it.
And here's where it gets even more interesting: There have been reports suggesting that even COVID-19 might lead to GBS in some cases. It's currently under investigation and has been highlighted in several studies.
Isn't it amazing (and a bit scary) how interconnected the world of viruses and our body's reactions can be?
Food Distribution & Campylobacter
When we think about food poisoning bacteria, there are quite a few culprits. But Campylobacter stands out in a unique way. Let's dive into why.
Firstly, Campylobacter prefers warm temperatures for growing, around 42°C, which is hotter than most other food poisoning bacteria. But more intriguing is that it won’t grow below 30°C. Think about it: how often is your room hotter than 30°C? Unless you're in a tropical region, not that often, right? So if chicken, which often carries Campylobacter, is left out at room temperature, the bacteria isn't likely to grow. That's a unique characteristic, especially when compared to other bacteria like E. coli and Salmonella, which grow at temperatures as low as 10°C.
So, even if there’s a slip-up in temperature control while distributing chicken, Campylobacter won't proliferate. Additionally, because it's "microaerophilic", it doesn’t grow well on most foods, including chicken.
Now, what does this all mean for us? Well, for Campylobacter, keeping food in the fridge or strictly managing its temperature doesn't really help in preventing its spread. And there's no point in developing antibacterial agents to suppress its growth in food either. The real challenge is managing the initial level of Campylobacter contamination in chicken farms and processing facilities.
In the U.S., for example, it's common to treat chicken with sodium hypochlorite at poultry processing facilities. However, there are emerging methods using a mix of peracetic acid and organic acids to remove Campylobacter.
Note: In the EU, they don't use chemicals like sodium hypochlorite in poultry processing. They even ban the import of chicken treated this way . Why? It's not just concerns over the chemical treatment itself, but a belief that relying heavily on such strong disinfectants might be a band-aid solution, masking potential hygiene issues earlier in the processing chain.
