A common, usually harmless group of bacteria linked to higher death rates in kidney patients

A large group of bacteria found in our soil, our water and our shower heads are harmless to most of us, but a new study shows they are linked to an increased risk of death in people with kidney failure.

In what appears to be the first study of its kind, researchers at the Medical College of Georgia and the Charlie Norwood VA Medical Center in Augusta looked at the US Renal Data System patients with the final stage kidney diseasesor ESRD who were also diagnosed with a nontuberculous mycobacterium infection, or NTM.

They found a significant and independent increase in mortality with a diagnosis of NTM in these patients, indicating that early diagnosis and treatment of NTM infection may improve survival in patients with ESRD, they report in Journal of Investigative Medicine.

“It’s important to be aware that some patients may be at greater risk for NTM and that NTM carries a mortality risk,” says Stephanie L. Burr, MD, an infectious disease physician at MCG and chief of the Division of Infection Control and Epidemiology at the Charlie Norwood VA Medical Center.

These “conditionally pathogenic” microorganisms, which were found even in dialysis machinestend to cause serious problems only when the patient has lung involvement or functions of the immune system.

Patients with kidney failure are thought to have compromised immune function and are generally considered to be at higher risk of infection, so MCG and VA researchers wanted to better determine the prevalence, risk factors, and associated death in those who also had NTM infection.

They looked specifically at 0.3% of the 1.1 million patients in the database with ESRD and a diagnosis of NTM in the decade ending in 2015. Patients were either on dialysis or had a kidney transplant.

“We looked for risk factors for the bacterium … and we looked at the different diseases it causes, e.g lung diseasesskin diseases and common diseases and looked at mortality in these patients,” says Baer, ​​corresponding author.

With a few exceptions, like skin diseaseShe says that NTM infection has almost always increased mortality in patients with ESRD.

The researchers emphasize that their findings highlight the need for physicians to remain vigilant about NTM infections in patients with TPN.

“This demonstrates a connection,” says co-author Wendy B. Bolag, Ph.D., a cell physiologist in MCG’s Department of Physiology. “We don’t know if NTM is the direct cause of mortality or if it’s more of a signal for the doctor to be aggressive with the patient at that point.”

This means that patients with ESRD may need to be tested for NTM if there are symptoms that indicate its presence and treated with appropriate antibiotics, they say. This may further mean that they need to be screened for conditions such as HIV, which directly affect the immune system, and those who have had a kidney transplant may need to have their medicines adjusted to prevent their immune system from attacking them on a transplanted organ.

To make sure they were looking at exactly the link between TPN and NTM, the researchers controlled for other known risk factors for contracting NTM, such as being black, having diabetes or liver disease, or HIV infection. The database did not contain information on other potentially confounding factors, such as BMI and blood levels of pro-inflammatory factors.

They found a higher risk of NTM infection with peritoneal dialysis compared with hemodialysis. Peritoneal dialysis can be done at home and uses cleansing fluid and the lining of the peritoneal cavity to filter waste compared to machine-assisted hemodialysis, but it’s not exactly clear why there is a difference. Rheumatic diseases such as arthritis, which may require drugs that suppress the immune response and such painful inflammation, also increase the risk of NTM, as does a history of organ transplantation, and the researchers note that due diligence is necessary in those with this added risk factors.

They noted that kidney transplant patients who had NTM infections were less likely to die, potentially due to factors such as recovery of kidney function, closer follow-up with health care providers, and that patients selected for transplant may be healthier. than those on dialysis. .

The database doesn’t specify which NTM was the most common, but they suspect it was the M. avium complex, which is by far the most common type in the southeastern United States, Baer says.

“It’s all around us. It can cause an allergy called hot tub cough or sneeze,” Baer says.

There are over 70 identified species of NTM and growing. These bacteria wrap themselves in a protective biofilm and become increasingly resistant to disinfectants and antibiotics.

NTM infection may cause nonspecific symptoms such as fever, weight loss, night sweats, and lethargy. Lung nodules and lymph nodes that do not resolve may be prominent signs.

“The good news is that it’s all around us and most of us never worry about it until it’s there immune system becomes compromised,” Bolag notes.

TPN and NTM infections are increasing, with the frequency of TPN being more than that tripling between 1990 and 2018, according to the Centers for Disease Control and Prevention. The increase in NTM is likely due to an aging COPD population and an increase in the number of people with weakened immune responses, Baer says.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, nearly 786,000 people in the United States have ESRD, 71% are on dialysis, and 29% have had kidney transplant.

Mycobacteria are a large group of organisms known to cause serious diseases such as leprosy and tuberculosis. NTMs are part of this group, excluding those that cause leprosy and tuberculosis.

The paper’s first author, Esther Toth, is an MCG medical student who is currently doing a year of research in the laboratory of Steven Holland, MD, director of the Division of Intramural Research and chief of the Immunopathogenesis Section at the National Allergy Institute. and infectious diseases.