National 17.9.2016 05:48 am

Killer TB lingers in lungs even after healing

A doctor examines a patient with Tuberculosis. (Photo by Gallo Images/Sunday Times/James Oatway)

A doctor examines a patient with Tuberculosis. (Photo by Gallo Images/Sunday Times/James Oatway)

PET/CT scans showed that only 14% of patients had no remaining inflammation in the lung after TB treatment was completed.

Stellenbosch University (SU) researchers have found evidence suggesting the bacteria causing tuberculosis often remains in the lungs after successful treatment. The research was recently published in the scientific journal Nature Medicine.

The study, conducted by the Immunology Research Group (IRG) at SU’s faculty of medicine and health sciences (FMHS), tracked areas of inflammation in the lungs of 99 HIV-negative adults in Cape Town that were diagnosed with TB.

PET/CT scans, which show advanced imaging that accurately shows sites of inflammation, performed during and after treatment showed that only 14% of patients had no remaining inflammation in the lung after TB treatment was completed.

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In 86% of the patients, some lesions with active inflammation remained, and in roughly a third of patients, new or apparently exacerbated lesions were seen despite most patients being cured.

Patients are considered cured if their symptoms improve and no TB bacteria are detected in sputum by standard tests.

“Previous research has shown that the TB bacteria have a remarkable ability to survive, even in the presence of antibiotics, and that these persisting bacteria are very difficult to detect or to destroy,” says the lead researcher, Dr Stephanus Malherbe, from the FMHS’s IRG.

In many patients, traces of TB in the form of mRNA was also detected in the sputum and fluid obtained through lung washings. “mRNA is a type of nucleic acid formed during metabolism and decays rapidly. Its presence would suggest there are still live bacteria in the lung after successful treatment,” says Malherbe.

“These findings point to a very important role for the body’s immune response to suppress or eradicate any residual live bacteria after treatment. This suggests treatment aimed at boosting the immune response may improve outcomes in the future,” Malherbe says.

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