An Australian woman has became the first documented person in the world to survive a pathogen that is usually the cause of the deadly “blackleg” disease in cattle and sheep.
The woman’s doctors this week published the case in the Medical Journal of Australia, detailing the successful treatment of the pathogen, after the only other two known cases in humans – one in the US and the other in Japan – had proved fatal.
Dr Ria Ko, the lead author of the article, was an infectious diseases advanced trainee at the Prince of Wales Hospital in Sydney when the 48-year-old woman presented last year with multi-organ failure, including of the liver and kidneys, and very low blood pressure.
The women was immediately admitted to intensive care with abdominal pain, diarrhoea, signs of shock and fever. Ko performed blood culture testing and discovered that a bacterium in the patient’s blood that she had never heard of before – Clostridium chauvoei – was the underlying cause of the infection.
When exploring exposure history of the patient, it is common with infectious diseases to ask about exposure to gardening soil. Ko discovered the woman had been in the process of moving houses and repotting her plants, and had scratches on her arms from her cats, who had been agitated by the change in the environment.
“We thought that the most likely point of entry for this bug would be from contaminated soil, with Clostridium chauvoei entering her bloodstream through these scratches,” she said.
While there was little in medical papers about how to treat humans infected with the bacteria, it was well known in the veterinary world as the leading cause of blackleg in cattle and sheep, Ko said.
In animals, when infected soil enters the bloodstream through cuts, it quickly causes myonecrosis, the death of the muscle in the legs, Ko said. “Sheep and cattle can’t complain or communicate they have this pain so we read in the literature that the most common presenting symptom of blackleg is death, because farmers find this animal dead and then find out they have blackleg.”
In her patient, the pathogen produced toxins causing necrotising enterocolitis, whereby sections of the bowel tissue die and can be described as “flesh-eating”, Ko said.
A/Prof David Beggs, a cattle veterinary specialist at the University of Melbourne, said the Clostridium bacterium that causes blackleg is a cousin of the bacteria that cause botulism and tetanus, which are also picked up from the soil and grow when they get into a nutrient-rich environment that has no oxygen.
Blackleg in cattle looks similar to gas gangrene syndrome in humans, where all the tissue around the infection dies and it becomes very gassy, Beggs said.
“What happens is typically the young calves look a bit lame and when you feel the leg where they’re lame, it feels like there’s a bubble wrap in there because the bacteria eat away at the flesh and cause gas to be produced.
“And the dead tissue that’s been macerated by the bacteria get into the bloodstream and cause blood poisoning. So you end up firstly with gangrene, which is just the tissue dying, and the gas getting there and then, secondly, with blood poisoning. Same in people.”
Over her first week, the woman made a relatively quick recovery, with her liver and kidney function improving after receiving antibiotics and hyperbaric oxygen therapy, a procedure used to increase the amount of oxygen reaching body tissue, Ko said.
She said hyperbaric oxygen therapy was used because there is some evidence for limiting the growth of Clostridium infection that has caused gas gangrene in diabetics’ foot infections.
The patient was discharged from intensive care on her fourth day in hospital. However, on the ninth day her abdominal pain returned and a CT scan revealed a hole in her bowel wall that required urgent surgery. “The pathologist was able to identify the area of bowel that was so thin, it was like paper thin … and then eventually perforated,” Ko said.
The woman was discharged from hospital two and a half weeks after the surgery. The academic paper said while the aggressive pathogen had until now been considered lethal, successful treatment was possible through a multidisciplinary approach.
Prof Anton Peleg, the head of infectious diseases at the Alfred hospital and Monash University, said the woman was “lucky” she survived the infection.
“There’s only been two other described cases in the literature of this type of bacteria, causing a severe infection, and in those cases, the two patients passed away,” Peleg said.
Ko’s publication comes less than a month after the world’s first case of a parasitic roundworm infecting a human’s brain made headlines and infectious diseases experts warned the threat of novel infections is rising.
Peleg said this case could also be classified as a zoonotic infection because it came from a bacterium that predominantly infects animals. However, he said “this case represents a very unusual scenario”.
“I don’t think this would be high on the list as a concern as increasing zoonotic infection in humans … as this would [not] be the start of a higher number of cases of this bacterial infection,” Peleg said.
Ko said the case was not a zoonotic disease in the traditional sense when the infection is directly transmitted from an animal. “It’s just that the bacterium often is more pathogenic in the livestock population, but it’s opportunistically also infected the human host this time.”
“The important thing is that this is not an infectious disease,” Beggs said. “The bacteria are commonly in the environment and there have to be a whole heap of circumstances that come together for cattle or humans to get infected with them.”
Peleg said the case highlights the importance of wearing gloves while gardening and washing hands afterwards. He said the other way the bacterium may have caused infection in the woman was if she ingested the bacterium’s spores into her gastrointestinal tract.
Ko also said ingestion was possible but there was no significant exposure to contaminated vegetables or fruit in the woman’s history.