Aspergillus and Mycobacterium are often seen together in respiratory samples such as sputum. This is known as ‘concomitant isolation’. The relevance of this in terms of infection, disease progression or the effect on other pre-existing conditions such as bronchiectasis, COPD or asthma, is poorly understood at the moment. There’s even debate over whether isolating both organisms from the same sample means that one or both are causing infection or just simply that they are both living in the individual without causing a problem.
A new study from researchers in France has attempted to understand how often concomitant isolation occurs and to better understand what this means for patients and their clinical outcomes.
The study looked back at 1384 patients in a hospital near to Paris who has positive cultures for Aspergillus (896) and Mycobacterium (488), over a 3 month period.
50 patients had at least one positive culture for both Mycobacterium and Aspergillus. The most commonly isolated Aspergillus species was Aspergillus fumigatus (33). Seven patients in the study had pulmonary aspergillosis. One third were immunocompromised and 92% had an underlying lung disease such as bronchiectasis.
The authors looked at data from blood samples, microbiology and scans to distinguish colonisation from infection. They concluded that while cases of the two organisms causing infections at the same time was rare, it is very important to perform all available tests and follow ups and discuss cases of co-infection or co-colonisation at multi-disciplinary team meetings to ensure that the best therapeutic decisions are made. This is especially important because development of chronic aspergillosis can worsen outcomes for patients already infected with Mycobacterium. Early diagnosis of CPA for patients with Mycobacterium is crucial.
In addition, the authors note that chronic lung conditions such as bronchiectasis might increase the likelihood of co-colonisation and so more work is needed to understand how the two organisms interact with each other in the lung.
More studies are also needed to see if these results are the same in other health care centres and hospitals and to see what differences, if any, are seen in patients colonised or infected by just one organism as well as both.
Read the full paper over on the Aspergillus website.