Increasing transmission of drug resistant tuberculosis in the UK

Download PDF Copy

May 1 2008

A changing population structure and ongoing migration have increased cases of drug resistant tuberculosis, according to a study published on bmj.com today.

The incidence of tuberculosis in England, Wales and Northern Ireland has been on the increase with more than 8000 cases reported in 2006. In addition, resistance to antituberculosis drugs has been increasing globally.

Of mounting concern is the increasing transmission of drug resistant tuberculosis among difficult to treat, marginalised groups in urban areas such as London, and the problems this could create for tuberculosis control.

Dr Michelle Kruijshaar and colleagues present the latest trends in resistance to antituberculosis drugs between 1998 and 2005 using data from the National Surveillance System, involving 28 620 confirmed cases of tuberculosis.

Overall, the researchers found that the proportion of cases resistant to any first line drug had increased from 5.6% to 7.9%. They report an increasing proportion of isoniazid resistance (6.9%) and small increases in rifampicin resistance (1.2%) and multidrug resistance (0.9%).

Importantly, outside London there was a significant increase in resistance to isoniazid. The authors suggest this reflects the increasing number of patients with tuberculosis who are not born in the UK. Analyses showed an increase in the number of cases in people from Sub-Saharan Africa and the Indian subcontinent that could be related.

In London, the rise in isoniazid resistance has been linked to an ongoing outbreak from 1999 that has involved over 300 cases to date. This outbreak has been associated with imprisonment and drug misuse and includes mainly the UK born population. The authors reinforce the importance of recognising symptoms early in this group.

They also note that the proportion of multidrug resistance showed a small increase (from 0.8% to 0.9%)-with the levels seen in the UK similar to those in other Western European countries-and suggest that most multidrug resistance cases occur due to problems with patient management rather than as a result of transmission within the UK.

These findings highlight the importance of early case detection by clinicians, rapid testing of susceptibility to drugs, additional support services to ensure that patients complete treatment, as well as continuous surveillance, and more help with tuberculosis control in countries with high incidence, conclude the authors.

The rising incidence of tuberculosis in the UK, combined with the rising proportion of resistant cases, increases the potential for onward transmission, warn the authors of an accompanying editorial.

James Lewis and Violet Chihota call for a range of strategies to be implemented including strengthening tuberculosis control and improving research into new diagnostics and drugs for multidrug resistant strains.

"Drug resistant tuberculosis in the UK cannot be controlled solely with local strategies -a global perspective is needed", they conclude.

What is tuberculosis (TB)?

Tuberculosis (TB) is a disease caused by germs that are spread from person to person through the air. TB usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, or the spine. In most cases, TB is treatable and curable; however, persons with TB can die if they do not get proper treatment.

What is multidrug resistant tuberculosis (MDR TB)?

Multidrug-resistant TB (MDR TB) is TB that is resistant to at least two of the best anti-TB drugs, isoniazid and rifampin. These drugs are considered first-line drugs and are used to treat all persons with TB disease.

What is extensively drug resistant tuberculosis (XDR TB)?

Extensively drug resistant TB (XDR TB) is a rare type of MDR TB. XDR TB is defined as TB which is resistant to isoniazid and rifampin, plus resistant to any fluoroquinolone and at least one of three injectable second-line drugs (i.e., amikacin, kanamycin, or capreomycin).

Because XDR TB is resistant to first-line and secondline drugs, patients are left with treatment options that are much less effective.

XDR TB is of special concern for persons with HIV infection or other conditions that can weaken the immune system. These persons are more likely to develop TB disease once they are infected, and also have a higher risk of death once they develop TB.

How does drug resistance happen?

Resistance to anti-TB drugs can occur when these drugs are misused or mismanaged. Examples include when patients do not complete their full course of treatment; when health-care providers prescribe the wrong treatment, the wrong dose, or length of time for taking the drugs; when the supply of drugs is not always available; or when the drugs are of poor quality.

How is TB spread?

Drug-susceptible TB and MDR TB are spread the same way. TB germs are put into the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings. These germs can float in the air for several hours, depending on the environment. Persons who breathe in the air containing these TB germs can become infected.

TB is not spread by