Medical Fun Facts Podcast

MFF0053: Flood water soft tissue infections

It’s Monday 3 April 2017. I hope you didn’t fall victim to any April fool’s day jokes on Saturday.

Australian listeners will know that over the last week we’ve witnessed Tropical Cyclone Debbie doing a number on the east coast of Australia with significant damage to parts of central Queensland and severe flooding in south-east Queensland and north-east New South Wales.

It got me thinking about water-borne soft tissue infections. So, as a little departure from the ‘diagnostics series’ I wanted to talk about water-borne soft tissue infections.

Tropical cyclones and tropical depressions causing severe flooding are common in Australia. As a result, soft tissue infections are also common during flooding events. I recall my first ‘learning’ of this during medical school, the late Richard Kemp explained the spike in infections after the 1974 Brisbane floods. Those floods ended the career of my grandparents as restaurant owners.

One of the most significant bacterial infections associated with water include soft tissue infection and septicæmia associated with my favourite bacterium, viz., Chromobacterium violaceum. Richard Kemp described a series of patients he’d seen who had very odd shoulder infections with at least one developing a septicæmia. All the patients were men, their ages ranged from early 20s to middle age and they were relatively fit. The infections were caused by Chromobacterium violaceum. It turns out, each of these men were assisting with flood relief and helping victims remove furniture and carpet from their sodden dwellings. It was common practice to roll carpet and then shoulder it to get out of the house. I don’t know if you’ve ever lifted a roll of carpet. The underside of it can be quite abrasive. The contaminated flood water had soaked the carpet and as abrasions formed on the shoulders of these men, they became infected with various bacteria. Some of the more severe infections were due to Chromobacterium violaceum.

Chromobacterium violaceum

I spoke about this in the wake of Tropical Cyclone Yasi in 2011. At the time, I was the Assistant Secretary for the Health Emergency Management Branch of the Office of Health Protection. I was giving evidence at Senate Budget Estimates on 31 May 2011. You can read the Hansard transcript. If you head to page 152 you can read what I said to the senators.

In that evidence, I also mention a couple of other favourite bacteria.

Aeromonas hydrophila and similar species in the genus Aeromonas can also cause very nasty soft tissue infections and septicæmia. This is particularly true for patients with liver disease. I recall there was an outbreak of infection near Collie in WA many years ago when some teenagers and young adults were playing a version of rugby known as mud football. The footy pitch was soaked in water from a local river water you can generate quite a lot of soft tissue infections.

There have also been reports of significant infections caused by aeromonads with no evidence of flooding or water. These have occurred in people who were camping in ‘dry’ river beds, they may have slipped and fell and had abrasions. The abrasions become infected and if left unchecked the infection can become quite severe.

Burkholderia pseudomallei

The final flood bacterium to discuss is Burkholderia pseudomallei. I could go on for hours about this bacterium. It was the mainstay of interest for me when I was working in Darwin. You can predict when the first cases of Melioidosis would occur when the first heavy rains would fall in the Top End. Like the other bacteria mentioned, Burkholderia pseudomallei is an environmental bacterium that lives in the water table. At the beginning of the wet season when the water table rises and the surface soil becomes damp, people exposed to the soil are prone to infection. It doesn’t happen to everyone, however, if you have a break in your skin or if you’re immunosuppressed because of diabetes mellitus, then soft tissue infection is common.

Specialist microbiologists and infectious diseases physicians are well versed in these sorts of infections and events, and many of us salivate at the prospect of growing these bacteria from clinical specimens. As I mentioned earlier, my all-time favourite bacterium is Chromobacterium violaceum and it’s because it is so pretty on an agar plate. These bacteria are known for their ability to produce a pigment called violacein. Production of violacein varies so that some variants are a light lilac while others are an intense purple that for all intents and purposes is black.

I truly hope none of the flood victims or the emergency services personnel become infected with any of these bacteria. They have the potential to be deadly. The good thing is that doctors trained locally in Queensland get taught about these infections in medical school and usually catch them early.

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