Multidrug-Resistant Infection Spreading Globally Among CF Patients

Mycobacterium abscessus poses new threat

A multidrug-resistant infection that can cause life-threatening illness in people with cystic fibrosis (CF) and can be passed from patient to patient has spread globally and is becoming increasingly virulent, according to new research published in Science.

The study, led by investigators at the University of Cambridge and the Wellcome Trust Sanger Institute in the United Kingdom, also suggests that conventional cleaning will not be sufficient to eliminate the pathogen, which can be transmitted through contaminated surfaces or in the air.

Mycobacterium abscessus, a species of multidrug-resistant mycobacteria, has recently emerged as a significant global threat to individuals with CF and other lung diseases. It can cause severe pneumonia leading to accelerated inflammatory damage to the lungs and may prevent safe lung transplantation, according to the researchers. It is also extremely difficult to treat––fewer than one in three cases is treated successfully.

It was thought that patients acquired the infection from the environment and that transmission between individuals never occurred. The researchers had previously studied one specialist CF center in the U.K. and identified genetic and epidemiologic evidence suggesting person-to-person transmission of M. abscessus, but it was unclear whether this was a one-off incident.

Now, by sequencing the genomes of more than 1,000 isolates of mycobacteria from 517 individuals attending CF specialist centers in Europe, the U.S., and Australia, the researchers found that most of the CF patients had acquired transmissible forms of M. abscessus that had spread globally. Further analysis suggested that the infection may have been transmitted within hospitals via contaminated surfaces and by airborne transmission. This presents a potentially serious challenge to infection-control practices in hospitals, according to the investigators.

Using a combination of cell-based and mouse models, the researchers showed that the recently evolved mycobacteria were more virulent and were likely to cause more-serious disease in infected patients.

“This mycobacterium can cause very serious infections that are extremely challenging to treat, requiring combination treatment with multiple antibiotics for 18 months or longer,” said Professor Andres Floto of the University of Cambridge. “The bug initially seems to have entered the patient population from the environment, but we think it has recently evolved to become capable of jumping from patient to patient, getting more virulent as it does so.”

One question that the researchers will now aim to answer is how the pathogen managed to spread globally. Their new study showed that not only can it spread between individuals within specialist centers, but it has also been able to spread from continent to continent. The mechanism for this is unclear, but the researchers speculate that healthy individuals may be unwittingly carrying the mycobacteria between countries.

The researchers’ sequencing data also revealed potential new drug targets, and the team is now working with other groups at the University of Cambridge and at Colorado State University in the U.S. to develop these targets further.

Source: University of Cambridge; November 10, 2016.