months is an alternative for those who are unable to take isoniazid or who have had known exposure to isoniazid-resistant TB. 3HR—Isoniazid and rifampicin may be given for 3 months. 2RZ—The 2-month regimen of rifampicin and pyrazinamide is no longer recommended for treatment of LTBI because of the greatly increased risk of drug-induced hepatitis and death. 3RPT/INH - 3-month (12-dose) regimen of weekly rifapentine and isoniazid. Evidence for treatment effectiveness: A 2000 Cochran review containing 11 double-blinded, randomized control trials and 73,375 patients examined six and 12 month courses of isoniazid (INH) for treatment of latent tuberculosis. HIV positive and patients currently or previously treated for tuberculosis were excluded. The main result was a relative risk (RR) of 0.40 (95% confidence interval (CI) 0.31 to 0.52) for development of active tuberculosis over two years or longer for patients treated with INH, with no significant difference between treatment courses of six or 12 months (RR 0.44, 95% CI 0.27 to 0.73 for six months, and 0.38, 95% CI 0.28 to 0.50 for 12 months). A 2013 systematic review published by the Cochrane Collaboration, compared Rifamycins (monotheraphy and combination therapy) to INH monotheraphy as an alternative in preventing active TB in HIV negative populations. The evidence suggested that shorter Rifampicin regimes (3 or 4 months) had higher treatment completion rates and fewer adverse events when compared to INH. However, the overall quality of evidence as per GRADE criteria was low to moderate. Another meta-analysis came to a similar conclusion, namely that rifamycin-containing regimens taken for 3 months or longer had a better profile in preventing TB reactivation. Research There is some evidence from animal and clinical studies that suggests that moxifloxacin-containing regimens as short as four months may be as effective as six months of conventional therapy. Bayer is currently running a phase II clinical trial in collaboration with the TB Alliance to evaluate shorter treatment regimens for TB; encouragingly, Bayer have also promised that if the trials are successful, Bayer will make moxifloxacin affordable and accessible in countries that need it. Another approach for anti-TB drug development, which does not rely on antibiotics, consists of targeting NAD+ synthase, an essential enzyme in tuberculosis bacteria but not in humans. Low level laser therapy for treating tuberculosis is not supported by reliable evidence. History Streptomycin and para-aminosalicylic acid were developed by the mid-1940s. In 1960, Edinburgh City Hospital physician Sir John Crofton, addressed