Bacteria threatens kidney transplant patients

Nocardia infections thrive in patients whose immune systems have been diminished by cancer treatment or organ transplants.

Dave Yasvinski 3 minute read October 12, 2021
Kidney transplant infection

Kidney transplant patients are at particular risk because the drugs required to stop an immune system from rejecting an organ also increase the risk of infection the longer they are taken.

A bacterium commonly found in soil and water presents a profound risk to the compromised immune systems of kidney transplant patients, causing pneumonia, brain abscess and even death, according to a new analysis.

The research, published in the Journal of Investigative Medicine, revealed that nocardia infections, which thrive in patients whose immune systems have been diminished by cancer treatment or organ transplants, represent a serious threat requiring the vigilance of healthcare professionals. Kidney transplant patients are at particular risk because the drugs required to stop an immune system from rejecting an organ also increase the risk of infection the longer they are taken.

While the dose and specific drug can be adjusted, this medicine is required as long as the transplanted organ remains in a new patient, according to Sandeep Padala, a nephrologist at the Medical College of Georgia and the Augusta University Health System. “Kidney transplant patients are at risk for all kinds of infections,” he said.

To determine the extent of the risk, researchers examined 203,233 kidney transplant recipients from the U.S. Renal Data System between 2001 and 2011, searching for patients who suffered from nocardiosis and failure of the kidney after infection, among other demographic factors. They found 657 patients, a lower percentage than previous studies, had experienced this infection; most patients were above the age of 65 and had received their kidneys from deceased donors, the most common source for transplants.

“Being older, having a brain abscess or being on specific immunosuppressants ended up translating to a higher risk of transplant rejection for these patients,” said Stephanie Baer, corresponding author of the analysis and an infectious disease physician at the Medical College of Georgia.

Recipients who developed the infection had been given widely used immunosuppressive drugs, including cyclosporine and tacrolimus. Those who were given a T-cell reducing drug called antithymocyte globulin before developing a brain abscess from a nocardia infection were the most likely to experience organ failure. Nearly 43 per cent of all patients examined experienced transplanted organ failure, a number that rose to 67 per cent among those with nocardia.

Surprisingly, transplant recipients with a history of organ rejection — common among those with nocardiosis — faced a decreased risk of subsequent organ failure, likely because doctors were on heightened alert to avoid a repeat occurrence, researchers said. They urged physicians to maintain this level of vigilance in all patients, especially those experiencing pneumonia and a brain abscess. “It they don’t respond to the routine antibiotics, then you have to start looking for unusual things,” Baer said.

“It’s a very difficult organism to both diagnose and treat because it’s a higher order bacteria; it’s more sophisticated than most bacteria. It only likes to infect specific places in the body like the lungs and the brain and you have to use special stains to see it.”

Treatment is complicated by the fact nocardia generally responds only to antibiotics that are toxic to the kidneys. It can also be confused with actinomyces, another type of bacteria found in the soil, meaning the prevalence of nocardiosis may be greater than the data suggests. According to the Centers for Disease Control and Prevention, nocardia can be acquired by digging in the dirt with a cut finger or just breathing in dust but it can also be transferred into a surgical wound if it is present on medical equipment — another factor behind calls for increased diligence.

Nocardiosis can be particularly devastating if the infection reaches the brain or spinal cord, with the CDC reporting up to 44 per cent of patients succumbing to the infection once it reaches this stage. According to researchers — who said less than 10 patients died among the 657 they studied — more research is needed to pinpoint the process of infection and develop strategies to treat patients while minimizing health risks.

Dave Yasvinski is a writer with Healthing.ca