Medical Fun Facts Podcast

MFF0015: Anthrax

Firstly an apology. I’ve been trying to produce a show on Mondays and Thursdays. Last night I ended up in a meeting and I then had to write a report. I didn’t finish that until late and I just decided no podcast. So sorry.

I bet you’re wondering why I’m mentioning anthrax on the podcast.

I tend not to mention work-related subjects so I’ll steer clear of that aspect of anthrax.

Did you know Australia has an anthrax belt that stretches from central NSW to northern Victoria?

I’ve been told that it was thought anthrax was relatively common in cattle which were driven by drovers when droving was common in Australia.

The Bacillus anthracis bacterium is fascinating.

Other Bacillus species, especially Bacillus cereus are relatively common to isolate in medical testing laboratories. Bacillus cereus can be found in specimens collected from superficial sites like skin. We also see it in blood cultures, most commonly as a contaminant. If you’re ever a patient in an emergency department and someone comes to collect blood for culture, make sure they disinfect your skin and wait for the antiseptic to dry before penetrating you with a needle. We’re really concerned from an infection rather than an intoxication perspective when the wounds are severe and associated with road trauma and the person suffers deep abrasions.  The other major concern we have about Bacillus cereus is food poisoning. This particular bacterium can produce toxins that can cause gastrointestinal problems. There are two types of food poisoning scenarios with Bacillus cereus, viz., vomiting which is caused by a toxin which is produced when the bacteria grow in the food, and diarrhoea which is also caused by a toxin but this happens when the bacteria are growing in your small bowel. The vomiting syndrome usually occurs soon after eating the ‘poisoned’ food and people recover usually within a day. For the diarrhoeal disease, the incubation time is usually between 8 to 16 hours and the diarrhoea can last for about 12 hours. In some people, it can run on for a few days. Did you like that pun?

Back to Bacillus anthracis the bacterium. Unlike other common species in the genus, the anthrax bacillus is not motile, it doesn’t produce hæmolysis on blood agar, and colonies have a ground glass appearance and exhibit tenacity when teased with a bacterial loop. I bet you’re wondering how to get a bacterial loop to tease a colony. Well, that’s a secret amongst microbiologists. By the way, do you know the collective noun for a group of microbiologists? We form a colony!!!

In clinical specimens like cerebrospinal fluid, the cells form long chains and look quite pretty.

Clinically anthrax the disease has many manifestations depending on the inoculating event.

Let’s think about cutaneous or skin infections first. But before that let’s back up and mention that Bacillus anthracis is a bacterium that can form spores. Bacteria change their metabolism and phenotype when environmental conditions become austere. It’s a survival tactic and the Anthrax bacillus is well known for its spore-forming capability.

So in cutaneous infection what usually happens is spores penetrate the skin and after a few days to a week, you’ll start to see a lesion which will slowly grow, it will become angry red and may ulcerate. If there are multiple penetrations of the skin, for example, if the skin has lots of abrasions and it’s exposed to lots of spores, multiple lesions can appear.

Oropharyngeal anthrax occurs when you eat contaminated food. This can result in outbreaks in settings where there may have been a feast on say contaminated water buffalo. A couple of days after eating the infected flesh, fever and neck swelling occurs as a result of infection of the oropharynx.

Fortunately, intestinal anthrax is relatively rare and occurs when eating undercooked infected meat. Abdominal pain and fever appear first followed by nausea, vomiting, malaise, loss of appetite, bloody vomit, bloody diarrhoea and sometimes watery diarrhoea. If not recognised and not treated promptly, death is rapid and the mortality is 50%.

Inhalational anthrax occurs when spores are inhaled. It happens in the textile and tanning industry when people work with contaminated animal products like wool, skins, and hides. Patients present with nonspecific low-grade fever, a non-productive cough, and may complain of discomfort in the middle of the chest. After initial improvement, bang, things go downhill and patients have a high fever, shortness of breath, they may go blue in the lips and face, they sweat like a pig, vomit blood and have chest pain similar to someone having a heart attack. If that’s not bad enough a complication of inhalational anthrax is septicæmic anthrax which occurs when everything starts going bad. The infection is in your blood and you get black blood. Black blood is never a good sign. Basically, you’re going to die.

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