Genome study reveals human-to-human spread of multidrug resistant mycobacterial infection

Using DNA tracking of an outbreak among cystic fibrosis patients at a treatment centre in the UK, the scientists identified frequent patient-to-patient transmission despite stringent infection control measures.

The authors warn that the findings, published Online First in The Lancet, will have major implications for how patients with are cared for in hospitals and raise critical questions about the adequacy of current infection control measures and the potential for cross-infection in other .

Estimates suggest between 3% and 10% of individuals with cystic fibrosis in the USA and Europe are currently infected with multi-drug resistant M abscessus and numbers are rising. The organism causes progressive lung damage and is extremely difficult to treat.

Andres Floto from the University of Cambridge, Julian Parkhill from the Sanger Institute, and colleagues used whole genome sequencing and antimicrobial susceptibility testing to compare the of individual M abscessus isolates from 31 infected attending the Cambridge Centre for at Papworth Hospital between 2007 and 2011.

They also used social network analysis to compare opportunities for cross infection between patients carrying genetically clustered and unclustered cases, and environmental testing to exclude obvious potential sources of infection such as bronchoscopes and .

Findings showed that two clustered outbreaks were caused by genetically identical or near-identical strains of M abscessus subspecies massiliense (from 11 patients), that differed by less than ten .

"Isolates from these 11 patients were often more closely related to each other than to other samples from the same individual, strongly suggesting that cross-infection has occurred widely between patients", explains Floto.

What is more, he adds, "this group of patients had numerous opportunities for within-hospital transmission from other individuals, while widespread environmental sampling failed to detect any specific source of exposure to NTM infection."

The team further cemented their theory of cross-infection by demonstrating that the clusters of M abscessus subspecies massiliense had evidence of transmission of mutations acquired during infection of an individual to other patients, and isolated bacteria with resistance to amikacin and clarithromysin from several patients with no history of long-term use of these antibiotics.

"The increased resolution provided by over previous typing techniques allowed us to clearly identify the existence, and in some cases the direction, of patient-to-patient transmission, something that would not previously have been possible"*, says Parkhill.

According to Floto, "Despite our evidence of transmission of M abscessus subspecies massiliense between patients, the exact mechanism of cross-infection remains to be established. Because of strict infection control policies, we believe that transmission probably occurred indirectly, for example via fomite (eg, hair, clothing, and bedding) contamination or aerosol generating procedures such as lung function testing."

More information: Josephine M. Bryant, Dorothy M. Grogono, Daniel Greaves, Juliet Foweraker, Iain Roddick, Thomas Inns, Mark Reacher, Charles S. Haworth, Martin D. Curran, Simon R. Harris1, Sharon J. Peacock, Julian Parkhill1and R. Andres Floto. (2013) 'Evidence for transmission of Mycobacterium abscessus between Cystic Fibrosis patients from whole-genome sequencing. Published in the Lancet online 29 March 2013. doi: 10.1016/S0140-6736(13)60632-7 http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(13)60632-7/abstract

Related Stories

Autophagy: When 'self-eating' is good for you

Apr 04, 2012

(Medical Xpress) -- New discoveries by Cambridge scientists about a molecular waste-disposal process that ‘eats’ bacteria are influencing the clinical management of cystic fibrosis, and could be ...

Recommended for you

Tracing the rise of Ebola in West Africa

9 hours ago

Since the Ebola outbreak first emerged in West Africa, The Associated Press has been reporting on it. A timeline compiled from AP dispatches since March shows the dreaded disease being identified in a remote ...

Spinal manipulation helps relieve back-related leg pain

9 hours ago

(HealthDay)—Adding spinal manipulative therapy (SMT) to home exercise and advice (HEA) may improve short-term outcomes in patients with subacute and chronic back-related leg pain (BRLP), according to research ...

User comments