Tuberculosis (TB) is a serious and life-threatening bacterial infection, and though it is treatable, more drug-resistant strains are emerging, limiting treatment options for patients. A team of Moroccan researchers are looking at the use of the polymerase chain reaction (PCR) to speed up diagnosis of tuberculosis and detection of resistance. This could help patients get the best possible treatment, and make a step towards thwarting the spectre of an epidemic of increasingly uncontrollable disease.
Around 5% of people with tuberculosis in 2010 had multidrug resistant (MDR) disease (resistant to at least isoniazid and rifampicin). The first case of extremely drug resistant TB (MDR plus additional resistance to a fluoroquinolone and any second-line injectable drug) was seen in 2005, and by January 2010, there had been at least one case in 58 different countries.
In research published in Infection and Drug Resistance, the team collected sputum samples from 100 new tuberculosis patients and 33 previously-treated individuals who had relapsed on treatment, or who had chronic disease. Using PCR and DNA sequencing, the researchers carried out mutation analysis of the rpoBI gene (linked to resistance to rifampicin), and the katG gene and inhA promoter region (linked with resistance to isoniazid).
This analysis found seven strains resistant to isoniazid alone; 17 resistant to rifampicin alone; and that nine people were carrying MDR (multidrug-resistant) TB strains. Of these, four had relapsed on treatment, four had chronic disease, and one was a new case. The most common mutation in the rpoB gene (making up almost half of the mutations in this gene) was a single base substitution. There was only one type of mutation in the katG gene.
According to the team, PCR has potential as an accurate and rapid method for detection of drug-resistant TB in clinical specimens, and could be of great interest in the management of TB in critical cases to help physicians choose the correct drug regime based on the strains and mutations in each individual. As well as improving the outcomes for patients, this kind of personalised medicine could also limit the emergence of MDR and XDR strains, which pose a threat to global tuberculosis management and control.
While xxpress PCR was not used in this research, its speed and thermal accuracy could provide the fast turnaround and reliable results required for this kind of application.
Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.