Drug Resistant Tuberculosis

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Drug resistant  TB (DR-TB) is the presence of bacilli resistant to one or more anti-tuberculosis medicines. Resistance patterns are defined as follows:

Mono-resistance

  • Resistance to one first line drug only (H, R, Z, E or S)

Poly-resistance

  • Resistance to more than one first line drug, excluding combination of H and R

Multidrug resistance (MDR-TB)

  • Resistance to at least both H and R

Fluoroquinolone resistant tuberculosis

  • Resistance to fluoroquinolones with or without resistance to other anti-TB drugs.

Rifampicin Resistance (RR)

  • Resistance to rifampicin with or without resistance to other anti-TB drugs, including any resistance to Rifampicin (i.e. including mono- and poly­ resistance.)

In Zimbabwe, most of patients are enrolled into the DR-TB treatment programme following an Xpert MTB/Rif test confirming resistance to rifampicin (MTB Detected/ Rif Resistance Detected.) Such patients receive the MDR-TB treatment regimen recommended (refer to Clinical Management of Drug Resistant Tuberculosis Guidelines).

While patients may have documented risk factors that predispose them to DR-TB, patients may also present with a primary episode of DR-TB with no apparent risk factors. Risk factors for developing DR­ TB (or worsening the pattern or resistance) include the following:

  • Patients who remain (or again become smear positive) during or after completing a TB treatment regimen.
  • Improper treatment of TB/DR-TB which includes treatment interruptions, incorrect doses for the patient's weight
  • Contact with a DRTB patient
  • HIV infection
  • Residence in high burden DRTB regions

The management of MDR-TB or XDR-TB cases is rapidly changing with emerging evidence on more patient friendly and effective regimens. The drugs and drug grouping used in the treatment of DR­ TB is shown in table below. For the latest guidance and practice recommendations on the management of DR-TB, please refer to the Clinical Management of Drug Resistant Tuberculosis Guidelines.

List of Drug Resistant TB (DR-TB) Medicines Used in Zimbabwe

Second-line medicines are B level medicines with V level of priority. However, second-line medicines are also to be found at primary health facilities for specific managing DRTB

Drug Grouping and Rationale

Medications

Group A

Drugs associated with improved outcomes and lower mortality in Individual Patient Data/meta analysis

Bedaquiline

Levofloxacin or Moxifloxacin

Linezolid

Group B

Drugs associated with improved outcomes in IPD/meta analysis

Clofazimine

Cycloserine

Group C

Remaining agents for regimen construction listed in order of priority for use

Ethambutol

Delamanid

Pyrazinamide

Carbapenems plus clavulanic acid

Amikacin, streptomycin

Ethionamide/prothionamide

PAS