Drug-resistant tuberculosis

Drug-resistant tuberculosis

          You can read articles from Bureau of AIDS, Tuberculosis and Sexually Transmitted Diseases, Department of Disease Control, Ministry of Public Health About drug-resistant tuberculosis here.

Drug-resistant tuberculosis (TB)

          Drug-resistant TB in Thailand has been a long-standing problem since the TB control program began almost 50 years ago. Because TB in Thailand is difficult to control, this causes frequent drug shortages and drug resistance. In the past, before 1985, a short-term 6-month drug treatment was used in tuberculosis patients. The problem of drug-resistant tuberculosis is not severe, and drug resistance has mainly been identified with resistance to isoniazid and streptomysin. The patients were still successfully cured using a rifampicin-containing regimen. The situation of drug-resistant tuberculosis persists after the application of short-term drug treatment. Last decade reported about the new drug-resistant TB, namely High multidrug resistance tuberculosis (MDR-TB), which can be found in many health cares or hospitals. The main cause of MDR-TB is that short-term drug treatment based on DOTS strategy is not effective. The problem with MDR-TB is likely to increase and become more complex due to the shortage of backup drug systems. Sometimes, patients in this group have ineffective behaviors for medication. Therefore, public health personnel caring for TB patients should have a good understanding of this issue.

Related definitions

Primary drug resistance is defined as resistance in untreated patients.

Acuquired drug resistance is defined as resistance in treated or ongoing patients.

MDR-TB is defined as resistance to at least two TB drugs, especially INH and Rifam, with or without other drug resistance

DOTS-Plus for MDR-TB is a TB care intervention to resolve and mitigate MDR-TB by using 2 linedrug (Cat4) under the DOTS system with drug susceptibility test results for consideration.

Who is likely to be MDR-TB? Principles of finding patients with suspected MDR-TB and determination of whether multidrug-resistant tuberculosis are important.

Patients who tend to be multidrug-resistant TB include:

           Patients with possibility of multidrug-resistant TB before treatment:

1. AIDS-infected patients, patients with a history of exposure with MDR-TB patients, including medical personnel.
2. Border prison patients

Patients with possibility of multidrug-resistant TB during treatment:

1. On treatment for cat 1, symptoms worsened with non-negative sputum at the end of the 2^nd month, and after 1 month of four-drug treatment, sputum remained positive.
2. On treatment of cat 1, results in treatment fail with the regular drug treatment, especially treatment with DOTS. This group is at high risk of MDR-TB.

On treatment of cat 2, the sputum results are not negative at the end of the 3^rd month of treatment.

On treatment of cat 2, the sputum results are not negative at the end of the 5^th month of treatment, the TAD that had returned and positive result in sputum.

Diagnosis of MDR-TB is essential to diagnose sputum or specimen with results indicating drug resistance. To support diagnosis, there are steps to operate as follows:

1. TB drugs should be discontinued 2 days before sending specimens for drug susceptibility test (DST).
2. To test drug sensitivity, the examination items or specimens should be sent from the hospital to be cultured for tuberculosis at the Office of Disease Prevention and Control for 2 days.
3. The results will be informed on website.

The primary care will be provided while waiting for DST in cases multidrug resistance is suspected. In the case of patients who tend to be multidrug-resistant tuberculosis, you should do the following:

1. Send sputum culture for DST.
2. While waiting for the results of the DST, the following guidelines should be followed:

2.1 In case of being treated with the cat1 drug system and the treatment result is failure, there are 2 options as follows:

2.1.1 Consider changing the drug system to a second-line drug system, that is, treatment with empiric cat4(1) drug system (Section 6.1).

1. 1. 2. Treat with the current cat1 drug system (H and R) and wait for DST results.

If treatment failure from the cat1 system and regular medication by DOT system is found, the cat 2 system should not be switched due to the low cure effect.

Guidelines for determining to comply with items 2.1.1 or 2.1.2, five criterias can be used to consider the possibility of multidrug-resistant TB as follows:

1. Clinical responses (cough, fever, changes in body weight)
2. Changes in sputum during treatment (Fall and rise)
3. History of receiving DOT in the previous treatment
4. Lung radiographs at the date of diagnosis of Cat 1 systemic treatment failure.
5. Having a history of risk factors for multidrug-resistant TB before treatment.

1. 2. In case of treatment with the cat2 system and treatment failure during DST, there are two alternative approaches: consider changing the system to a second line system, i.e., treatment with empiric Cat4(2) system. (Section 6.2). The cat2 (HR, R and E) system is applied first and wait for the DST result.
   3. For other cases, the patient's current medication system should be given first and DST results should be awaited.

3. When DST results are returned, there are guidelines for applying DST results to modify the drug system as follows:

1. 1. In case of items 2.1 and 2.2, if treatment while waiting for the DST results still uses the same drug system, the drug should be adjusted according to the DST results.
   2. In case of items 2.1 and 2.2, if an empirical Cat 4(1) or empirical Cat 4(2) dosing system has already been initiated during waiting for the DST results, the drug should be adjusted according to the DST results based on sputum response during complementary second-line anti-TB therapy. It is sometimes possible to continue with the empirical Cat 4(1) or empirical Cat 4(2) regimen.
   3. Other cases besides items 2.1 and 2.2
      1. If the DST result is MDR-TB, the DST results of the 7-drug system or the basic drugs will be used for treatment together with the DST-based drug system using the principles in item 7 (Treatment for MDR cases).
      2. If the DST result is not MDR-TB, the clinical response and sputum direct smear results should be considered while waiting for the DST result. In some cases, the previous drug system can be used without switching to TB medication line 2.

If DST results, clinical response, and direct smear results are not related, a history of regular medication, the clinical response, and direct smear results will be mainly considered for determining which drug system should be used. In the case of using line 2 TB drugs, item 7 should be applied. DOT should be done by health officers or doctor.

Thank you

Bureau of AIDS, Tuberculosis and Sexually Transmitted Diseases, Department of Disease Control, Ministry of Public Health.