To the Editor:
Extensively drug-resistant tuberculosis (XDR-TB) (defined as TB caused by Mycobacterium tuberculosis strains with in vitro resistance to isoniazid and rifampicin plus any fluoroquinolone and at least one of the second-line injectable drugs, amikacin, capreomycin or kanamycin) on top of being a growing public health concern, represents a nightmare for the clinician [1–4]. The crucial therapeutic issue is the difficulty of identifying at least four available “active” anti-TB drugs, to ensure treatment success as well as to prevent the emergence of additional drug resistance [1–4].
After more than 40 years without new anti-TB drugs appearing on the horizon, new chemical compounds (i.e. bedaquiline, PA-824 and delamanid) seem promising for these difficult-to-treat cases of TB [4, 5].
While the necessary experimental studies will prove how to use them, more and more interest is currently focused on existing antibacterial drugs with new indications for drug-resistant TB, particularly linezolid, meropenem, clofazimine and cotrimoxazole [6–9].
Based on in vitro and pharmacological data, suggesting that linezolid (an oxazolidinone antibiotic) could be efficacious in treating mycobacterial infections, and on anedoctal evidence of its effectiveness in the smallest groups of patients, it was used off-label, despite its high price, to treat multidrug-resistant (MDR) TB cases in several countries. The little scientific supporting data on the efficacy, safety and tolerability of linezolid came from ad hoc randomised, controlled clinical trials, as well as from large observational studies [7].
The European Respiratory Journal recently published a systematic review and a meta-analysis of individual patients focused on the main published epidemiological observational studies (n=12), describing cohorts of TB patients (n=121) treated with linezolid-containing regimens in 11 countries [7 …
