Probiotic supplement caused man's fatal infection in rare case

In a rare case, a man died of a bloodstream infection that was triggered by a probiotic supplement.

These blood infections, known as probiotic-related bacteremia, are a known risk of taking probiotics, or live microorganisms that are meant to benefit the body in some way — for example, by repopulating the gut microbiome after a person takes antibiotics. Probiotic-related infections happen only occasionally, but having a weakened immune system or abnormalities in the gastrointestinal tract may raise the risk.

Various case reports have described incidents in which hospitalized patients ended up with bacteria in their blood after being given probiotics. More-detailed studies, including one published in 2019, have uncovered genetic evidence that the exact bacteria in a given probiotic were the culprit behind a patient's infection.

In the man's recent case, a genetic analysis confirmed that bacteria from a probiotic triggered his fatal infection. A description of the man's case was published Aug. 3 in the journal BMJ Case Reports. It noted that the patient had an extensive medical history, which likely raised his risk of this rare occurrence.

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The case began when the man, who was in his 70s and lived in Japan, was found collapsed on the floor of his home and then brought to an emergency room. Doctors found that the patient had severe metabolic acidosis, in which acid builds up in the blood. This condition had been brought on by a lung infection, a kidney injury and, potentially, heavy drinking, as the man had a history of alcohol dependence.

Further tests revealed that the man was positive for SARS-CoV-2, the virus behind COVID-19. He was transferred to an intensive care unit and received breathing support; a blood thinner; a steroid to combat inflammation; and tocilizumab, which blocks an inflammatory protein. He also got antibiotics, as doctors suspected and then confirmed that he also had a bacterial infection at the same time.

The antibiotics were needed but also gave the patient diarrhea, so his doctors also prescribed a probiotic containing a strain of Clostridium butyricum, which is widely used and has a strong safety profile. Studies suggest it's found in the guts of about 20% of healthy individuals. When given as a supplement, C. butyricum is thought to make the gut less favorable to pathogens and more favorable to helpful bacteria that aid in digestion and tamp down inflammation.

However, in this instance, the probiotic went rogue.

The man had been discharged from the ICU after about a month in the hospital and was undergoing rehabilitation in the general ward while taking the probiotic. Then, after nearly two months in the hospital, the patient developed fatigue, swelling and "severe, continuous" pain in his abdomen. Body scans revealed a dangerous lack of blood flow to the man's intestines.

While investigating the man's symptoms, the medical team also took a blood sample and found that C. butyricum bacteria grew in the sample. Blood is generally considered sterile, so this can be taken as a confirmation of a bloodstream infection. A close analysis of the grown microbe's genome confirmed that it was "identical" to that of the bacteria in the probiotic.

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Unfortunately, "the patient rapidly developed multiorgan failure," and surgery could not be pursued due to his unstable condition. "His treatment was transitioned to palliative care and he died on the 60th hospital day," the case report authors wrote.

Although probiotics have been used for many decades, this report and others like it raise concerns about otherwise-accepted products, the case report authors argue. And this isn't the first case involving this particular strain of C. butyricum, given that it is widely used, especially in Japan.

Probiotic-related bacteremia is seen most often in older patients with multiple medical conditions, such as a weakened immune system, chronic kidney disease, rheumatoid arthritis or gastric cancer. In this case, the patient was older and had a medical history that included smoking, colon cancer, high blood pressure and chest pain due to heart disease.

In addition, he was given a steroid, which can suppress the immune system, to treat his COVID-19 infection.

"While probiotics are routinely prescribed among ill patients with various gastrointestinal symptoms and conditions," the authors wrote, "rare yet severe adverse events may occur, as exemplified in this report."

This article is for informational purposes only and is not meant to offer medical advice.

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