Virulent Bacteria Strain Poses Particular Risk to CF Patients, Study Warns

An infection caused by Mycobacterium abscessus, a species of multi-drug resistant mycobacteria, is a growing threat to cystic fibrosis (CF) patients, researchers in the U.K. warn. The infection shows signs of being increasingly contagious, and increasingly virulent.

The study reporting on the bacterium — which can cause severe pneumonia and has been identified in patients at CF treatment centers — is titled “Emergence and spread of a human-transmissible multidrug-resistant nontuberculous mycobacterium,” and was published in the November edition of the journal Science.

Led by researchers at the University of Cambridge and the Wellcome Trust Sanger Institute, the study suggests that conventional cleaning methods may not be effective in eliminating this bacterium, which, the researchers said, appears to be both airborne and transmitted through contaminated surfaces.

An earlier study the team conducted at one U.K. specialist center for CF patients suggested person-to-person transmission was possible, and that finding may have been confirmed through a newer and larger study in more than 500 CF patients carrying the bacterium.

“This mycobacterium can cause very serious infections that are extremely challenging to treat, requiring combination treatment with multiple antibiotics for 18 months or longer,” Andres Floto, professor from the Department of Medicine at the University of Cambridge, said in a press release. “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.”

M. abscessus, by causing severe pneumonia, can accelerate inflammation in the lungs, and may prevent a safe lung transplant. The infection is increasingly difficult to treat, with success rates as low as one in three, the researchers said.

The team did whole genome sequencing on more than 1,000 mycobacteria isolates from 517 patients being treated at CF centers across Europe, the U.S., and Australia. Their findings revealed that most of the CF patients had transmissible forms of M. abscessus, with isolates found worldwide.

“We show that the majority of M. abscessus infections are acquired through transmission, potentially via fomites [infected objects] and aerosols, of recently emerged dominant circulating clones that have spread globally,” the researchers wrote. “We demonstrate that these clones are associated with worse clinical outcomes, show increased virulence …  and thus represent an urgent international infection challenge.”

To reduce the risk of transmission, the Adult Cystic Fibrosis Centre at Papworth Hospital has implemented new infection control policies, many of which have been adopted across the U.K. A new hospital CF unit, opening on the Biomedical Campus of the University of Cambridge in 2018, will also incorporate an air handling system designed to prevent the spread of airborne infections.

The researchers now are looking into how the pathogen spreads, studying its underlying mechanisms, and exploring the possibility that healthy individuals might be carrying the mycobacteria from country to country.

“Our research should provide a degree of hope: now that we know the extent of the problem and are beginning to understand how the infection spreads, we can start to respond,” said Professor Julian Parkhill with the Wellcome Trust. “Our work has already helped inform infection control policies and provides the means to monitor the effectiveness of these.”

Genome sequencing of the mycobacteria isolates also revealed potential new drug targets, and the team is working on developing these further.