Published: July 26, 2007
We share in the optimism associated with the recent news that indicates patients originally identified with extensively drug-resistant tuberculosis (XDR TB) may have additional drug treatment options. Yet, the reality remains that these patients and many others across the world are suffering from a very serious form of multi-drug resistant tuberculosis (MDR TB). Drug-resistant TB poses a grave and growing threat to global public health which we as a nation must take action to address.
We must ensure that the public health messages and necessary responses to drug-resistant tuberculosis are not quickly forgotten, but rather propel us toward new solutions. First, it is critical that we ensure that the public understand the basic facts about how this disease evolves, how it is transmitted, and how to protect their own health and that of others. Like many infectious diseases, tuberculosis takes weeks to months to identify or diagnose, is challenging to treat and can sometimes be spread by people who don't appear to be ill. The challenging nature of TB also means that effectively treating it, and preventing its transmission, requires a sustained partnership between health care providers, local and state public health practitioners and patients infected with the disease.
Second, it is worth reiterating that anyone with active TB disease, regardless of whether it is drug-resistant, should avoid situations that place them in prolonged contact with others, including flying on commercial aircraft. TB is generally not spread by casual contact, but typically requires relatively prolonged contact in shared airspace. The environment on long flights in commercial aircraft, particularly those of eight or more hours in length, has been previously implicated in TB transmission, especially to passengers seated in close proximity. This is the basis for the World Health Organization (WHO) guidelines for the prevention of TB transmission during air travel. Protecting the health of international air travelers requires building and sustaining partnerships between public health and infected individuals.
Third, in moving forward, we need to increase our efforts to communicate strongly and clearly about risks posed by tuberculosis; strengthen our efforts to reduce the fear and stigma associated with this devastating disease; and clarify and reinforce the roles that patients, clinicians, and public health officials play in infectious disease control.
There's no doubt we have had considerable success in TB prevention and control in the United States. There's also no doubt the increasing prevalence of drug-resistant tuberculosis bacteria across the world is a reminder that much more needs to be done. Beyond improved awareness and education, scientific advances will also be required to reduce the threat of this disease. The current methods to diagnose TB are complex, are not available everywhere they are needed, and require far too much time to provide results. New methods are needed that can give us reliable answers in hours or days instead of weeks. Similarly, new safe and effective vaccines and treatments are urgently needed to combat drug-resistant TB bacteria to prevent a return to the pre-antibiotic era.
Effective public health response to MDR and XDR TB requires accelerated efforts and earnest engagement by multiple sectors of society. All of us—patients, providers, health officials, and policymakers—share a responsibility to take action now to prevent further transmission.
Martin S Cetron, MD
Captain, U.S. Public Health Service
Director, Global Migration and Quarantine
Centers for Disease Control and Prevention
Kenneth G. Castro, M.D.
Assistant Surgeon General, U.S. Public Health Service
Director, Tuberculosis Elimination
Centers for Disease Control and Prevention
How can drug susceptibility testing have different results on specimens from the same patient?
TB bacteria can show variable resistance to second-line TB medications. Thus, a change or difference in test results can, and does, happen when it comes to MDR and XDR TB. Different specimens/samples from the same person can produce different results. The patient may also be infected with more than one strain of TB. TB that consists of more than one strain is not uncommon. For example, in one recent study, 19% of patients were infected with two different strains of TB at the same time. [Reference: Warren RM et al. Patients with Active Tuberculosis often Have Different Strains in the Same Sputum Specimen. Am J Respir Crit Care Med 2004;169:610-4.]
What is extensively drug resistant tuberculosis (XDR TB)?
XDR TB is a more serious form of multidrug-resistant TB (MDR TB). In both cases, the TB is resistant to the "first-line" antibiotics available for treatment, as well as some of the second-line antibiotics. Both MDR TB and XDR TB, are difficult to treat and are often fatal. 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 second-line drugs, patients are left with very limited treatment options that are even less effective than for MDR TB that does not qualify as XDR TB.
What is drug susceptibility testing?
Drug susceptibility testing uses laboratory techniques to determine which medicines will kill the TB bacteria in the patient's specimen. The results of drug susceptibility tests can help clinicians choose the appropriate treatment regimen for each patient.
What can be done to improve our ability to prevent and reduce the numbers and cases of TB?
New tools for TB diagnosis, treatment, and prevention are needed to achieve the goal of TB elimination. New diagnostic tools for TB detection, especially drug-resistant TB, are needed. Rapid diagnostic tests, such as those that have been developed for HIV, are still unavailable for drug-resistant TB.