Flesh-eating bacteria strips skin off leg of River Murray boatie

by Daniel Keane on 10 Mar 2017 Murray Bridge man Bill Andrews had never heard of Shewanella bacteria until days after it entered his left leg, causing a horrifying flesh-eating infection. 'It just felt like somebody was down there with a saw going to cut my leg off,' he said. 'I woke up with throbbing in the leg. I switched the light on to have a look and it was about the size of a football, my left ankle. I had to go to the toilet. I got only about two thirds of the way to the bedroom and I collapsed on the floor.'

Mr Andrews' case of a flesh-eating Shewanella infection is believed to be the first ever reported in South Australia. He ended up losing about 20 per cent of the flesh in his calf. Mr Andrews said he was at his local boat ramp at Hume Reserve on the River Murray waterfront when, he suspects, the bacteria made its way through a scratch in his skin. 'Worst-case scenario would have been, had it been left much longer, I would have lost my leg,' he said.

'I've had three skin grafts — two of them approximately two inches wide by eight inches long. The other one is about three inches by three inches. 'I've more or less got to start learning to walk again.

Fewer than 300 cases in 35 years: SA Health

At first, Mr Andrews went to the Murray Bridge hospital, but it was only after blood tests were carried out at the Royal Adelaide Hospital that the infection was diagnosed. SA Health said it was extremely rare for the bacteria, which is found in sea and fresh water as well as the soil, to cause a flesh-eating infection. 'Shewanella is fairly common but infection isn't,' SA Health water quality advisor David Cunliffe said.

'There was a recent survey published and they looked at all reported cases worldwide, and they found less than 300 cases (this extreme) in the last 35 years. Depending on underlying conditions, it can be fatal.'

Dr Cunliffe said while it was an alarming example of Shewanella infection, there was little need for public concern. 'If you do have a wound or skin abrasion or skin lesion, keep it covered,' he said. 'But we don't want to give the message that the River Murray is a dangerous place. It's not sterile but (it) is a place where you can enjoy yourself and the chances of getting an infection like this are extremely low.'

But Mr Andrews, who is recovering with the help of a walking frame, believes his case should serve as a warning to river users. 'I'll never go in there again unless I've got waders on.'

MicrobeWiki has this to say about the bacteria:

Shewanella putrefaciens is a bacteria that is found mainly in marine environments. It is a gram negative bacteria, meaning it does not dye during gram staining, which usually indicates a stronger antibiotic resistance. It is also a facultative anaerobe, meaning it can undergo aerobic respiration when oxygen is present, and can reduce iron and magnesium metabolically.

Because of this Shewanella putrefaciens can reduce Uranium and create uranium deposits (Fredrickson). Sheweanella putrefaciens grows quickly on both solid and liquid media and is recognizable for its pink color. Shewanella putrefaciens was first isolated from dairy products in 1931 by Derby and Hammer. It is classified as an Achromobacter and later named by MacDonell and Colwell in 1985 (McNair).

Effect on Marine Life

Shewanella putrefaciens can be found in freshwater, brackish, and salt water ecosystems. Many healthy marines animals are contaminated with Shewanella putrefaciens only to have it be realized when food caught by seafood industries spoils due to the bacteria’s presence. In freshwater animals, and in particular fish species of trout, the bacteria has been shown to cause disease. The effect of the bacteria is seen through external lesions and visible bacterial colonies. Fatality from Shewanella Putrefaciens usually only occurs if the fish are already in poor health, under environmental stress or a whole body inner infection occurs that impedes organ function (Fisheries).

Most research done on Shewanella putrefaciens in relation to marine life concentrates on the prevention of bacterial outbreaks in fisheries. Much of the problem in prevention comes from Shewanella's tendency to become a contaminant or saprophyte, meaning it is often found living among other bacterial infections on previously damaged organs, as well as the bacteria's ability to survive at extreme low temperatures and respiratory diversity (Hau). These things combined make the bacteria hard to detect until after the death of an organism, and hard to kill without the use of antibiotics. Shewanella putrefaciens is also known to cause the rotting smell associated with dead fish because of its production of trimethylamines (McNair)

Impact on Humans

Shewanella putrefaciens as a human’s pathogen is very rare. If it does effect human health it is typically only seen to show effects in combination with other bacterial infections such as E.coli, pneumonia, and streptococcus. Infections form Shewanella putrefaciens mainly occur in soft tissue such as skin, intra-abdominal areas, or in the blood (Pagani) (McNair).

Shewanella putrefaciens is a main food spoilage bacteria in marine fish, which in turn can effect human health, but also creates a problem for the food industry. It also possess an even larger problem for the food industry because of its ability to form film on the food processing equipment that is mainly made of stainless steal.

Studies done by Applied and Environmental Microbiology society looked deeper into this problem and the possibility that Shewanella Putrefaciens colonies on the equipment may be the source of further bacterial pollution while also causing corrosion of the equipment itself. The persistence of Shewanella putrefaciens colonies on the equipment, even after disinfection, is partially due to the fact that it is a gram negative bacterium that has a higher resistance to antibiotics.

The results of this study showed that although disinfection did not have a significant impact on Shewanella putrefaciens growth on the equipment, the presence of the bacteria P. fluorescens did inhibit growth. This is due to the fact Shewanella putrefaciens tends to grow in 'microbial communities' where other bacteria is part of the film formed. When P. fluoresens is present in microbial film with Shewanella putrefaciens it outcompetes and limits its growth (Bagge).

Conclusion

Shewanella putrefaciens is also well known for its use in biotechnology. Shewanella putrefaciens is a metal reducing, facilitate anaerobe and this quality contributes to its ability to be used in biotechnology. It is used as many things from a bioremediate of chlorinated compounds to a radionuclide and a biocatalyst. Its ability to be a biocatalyst and to reduce iron has led to interesting research done with Shewanella putrefaciens being used in fuel cells. This research is being done at the Korean Institute of Science and Technology and has shown that Shewanella has the ability to be used in a fuel cell as part of a biosensor for lactate.

This means with the presence of Shewanella putrefaciens as an electron acceptor and metal reducer of iron was a change of charge detected in the fuel cell when lactate was added. This presence of an electrochemical reaction could mean a lot of things for the use of Shewanella putrefaciens in fuel cells later on (Kim). The bacteria has also been shown to derive energy by reducing uranium, manganese, Vanadium, and Technetium (Min).