The Group A drugs are currently levofloxacin or moxifloxacin, bedaquiline and linezolid, therefore XDR-TB is MDR/RR-TB that is resistant to a fluoroquinolone and at least one of bedaquiline or linezolid (or both). In a study of MDR-TB patients from 2005 to 2008 in various countries, 43.7% had resistance to at least one second-line drug. About 9% of MDR-TB cases are resistant to a drug from both classes and classified as XDR-TB.In the past 10 years TB strains have emerged in Italy, Iran, India, and South Africa which are resistant to all available first and second line TB drugs, classified as totally drug-resistant tuberculosis, though there is some controversy over this term. Increasing levels of resistance in TB strains threaten to complicate the current global public health approaches to TB control. New drugs are being developed to treat extensively resistant forms but major improvements in detection, diagnosis, and treatment will be needed. Prevention
There are several ways that drug resistance to TB, and drug resistance in general, can be prevented:
Rapid diagnosis & treatment of TB: One of the greatest risk factors for drug-resistant TB is problems in treatment and diagnosis, especially in developing countries. If TB is identified and treated soon, drug resistance can be avoided. Completion of treatment: Previous treatment of TB is an indicator of MDR TB. If the patient does not complete their antibiotic treatment, or if the physician does not prescribe the proper antibiotic regimen, resistance can develop.
Ciprofloxacin should not be used in the treatment of tuberculosis if other fluoroquinolones are available. As of 2008, Cochrane reports that trials of other fluoroquinolones are ongoing.There is no intermittent regimen validated for use in MDR-TB, but clinical experience is that giving injectable drugs for five days a week (because there is no-one available to give the drug at weekends) does not seem to result in inferior results. Directly observed therapy helps to improve outcomes in MDR-TB and should be considered an integral part of the treatment of MDR-TB.Response to treatment must be obtained by repeated sputum cultures (monthly if possible). Treatment for MDR-TB must be given for a minimum of 18 months and cannot be stopped until the patient has been culture-negative for a minimum of nine months. It is not unusual for patients with MDR-TB to be on treatment for two years or more.Patients with MDR-TB should be isolated in negative-pressure rooms, if possible. Patients with MDR-TB should not be accommodated on the same ward as immunosuppressed patients (HIV-infected patients, or patients on immunosuppressive drugs). Careful monitoring of compliance with treatment is crucial to the management of MDR-TB (and some physicians insist on hospitalisation if only for this reason). Some physicians will insist that these patients remain isolated until their sputum is smear-negative, or even culture-negative (which may take many months, or even years).