Title: Drug sensitivity testing (DST)
Course: Communicable Diseases Part 2 - Ethiopia (Full)

Drug sensitivity testing (DST)

Drug sensitivity testing (DST), performed in a reference laboratory, is the only means by which resistance to anti-TB drug(s) can be confirmed. DST involves growing TB bacteria and treating the culture with one or more anti-TB drugs and seeing if the bacteria are killed or not. If the bacteria are not killed by giving the drug(s), they are considered resistant.

Table 16.2 makes the point that there are three sources for the development of drug resistance. The first and most important category reflects shortcomings by health providers — they can give an inadequate drug regimen, or the wrong guidelines, or they can fail to treat correctly through lack of training and a poor monitoring system. The second category is related to the drugs themselves — they can be of poor quality, in short supply or they can be poorly stored. The last factor contributing to the development of drug resistance relates to the TB patients themselves, and reflects factors such as poor adherence, lack of information about the disease and the influence of social barriers, any one of which can result in patients discontinuing the drugs.

Table 16.2 Causes of inadequate anti-tuberculosis treatment contributing to development of MDR-TB.

Healthcare providers | Drugs | Patients
Inadequate regimens

Inappropriate guidelines

Non-compliance with guidelines

Absence of guidelines

Poor training

No monitoring of treatment

Poorly organised or funded TB control programmes
Inadequate supply

Poor quality

Unavailability of certain drugs (stock-outs or delivery disruptions)

Poor storage conditions

Wrong dose or combination
Inadequate drug intake

Poor adherence (or poor DOT)

Lack of information

Lack of money (no treatment available free of charge)

Lack of transportation

Adverse side-effects

Social barriers

Poor absorption of drugs

Substance dependency disorders

Treatment of MDR-TB is more complicated and takes longer than treatment of TB that is not resistant to the first-line drugs. In Ethiopia, the management of MDR-TB is currently available only at St Peter Specialized TB hospital, but there are plans to expand provision to other regions. As a health worker, the most significant way in which you can help now and in the years ahead is to do all you can to ensure that patients adhere to their treatment, in order to increase the number of cured cases and reduce the incidence of drug-resistant TB.