Tuberculosis (cont.)

Drug-resistant TB (TB that does not respond to drug treatment) has become a very serious problem in recent years in certain populations. For example, INH-resistant TB is seen among patients from Southeast Asia. The presence of INH-like substances in the cough syrups in that part of the world may play a role in causing the INH resistance. Drug-resistant cases are also often seen in prison populations. However, the major reason for the development of resistance is poorly managed TB care. This can result from poor patient compliance, inappropriate dosing or prescribing of medication, poorly formulated medications, and/or an inadequate supply of medication. Multidrug-resistant tuberculosis (MDR-TB) refers to organisms that are resistant to at least two of the first-line drugs, INH and Rifampin. More recently, extensively (extremely) drug-resistant tuberculosis (XDR-TB) has emerged. These bacteria are also resistant to three or more of the second-line treatment drugs.

XDR-TB is seen throughout the world but is most frequently seen in the countries of the former Soviet Union and Asia.

Preventing XDR-TB from spreading is essential. The World Health Organization (WHO) recommends improving basic TB care to prevent emergence of resistance and the development of proper laboratories for detection of resistant cases. When drug-resistant cases are found, prompt, appropriate treatment is required. This will prevent further transmission. Collaboration of HIV and TB care will also help limit the spread of tuberculosis, both sensitive and resistant strains.

Conceivably, TB could have been eliminated by effective treatment, vaccinations, and public-health measures by the year 2000. However, the emergence of HIV changed the whole picture. Because of HIV, a tremendous increase in the frequency (incidence) of TB occurred in the '80s and throughout the '90s. This increase in TB happened because suppression of the body's immune (defense) system by HIV allowed TB to occur as a so-called opportunistic infection. With the increasing HIV epidemic in Africa, serious concerns are being raised about the development of MDR-TB and XDR-TB in this population. Hopefully, control of HIV in the future will check this resurgence of tuberculosis.

The epidemic of HIV and TB has been a deadly combination especially on the African continent. A recent study comparing prophylactic regimens for prevention of active TB in HIV-infected individuals has shown effectiveness, however, the distribution of medication for both of these disease in the third world remains problematic.

Previous contributing author and editor:

Medical Author: Zab Mohsenifar, MD
Medical Editor: Leslie J. Schoenfield, MD, PhD

REFERENCES:

Cuevas, et al. "A Multi-Country Non-Inferiority Cluster Randomized Trial of Frontloaded Smear Microscopy for the Diagnosis of Pulmonary Tuberculosis." PloS Medicine 8.7 (2011).

Cuevas, et. al. "LED Fluorescence Microscopy for the Diagnosis of Pulmonary Tuberculosis; A Multi-Country Cross-Sectional Evaluation." PloS Medicine 8.7 (2011).

Martinson, N.A., et al. "New Regimens to Prevent Tuberculosis in Adults With HIV Infection." NEJM 365 July 7, 2011: 11-20.

United States. Centers for Disease Control and Prevention. "Guidelines for the Investigation of Contacts of Persons With Infectious Tuberculosis and Guidelines for Using the QuantiFERON-TB Gold Test for Detecting Mycobacterium tuberculosis Infection, United States." MMWR 54(No. RR-17) 2005.

United States. Centers for Disease Control and Prevention. "Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection -- United States, 2010." MMWR 59 (No. RR-5) June 25, 2010: 1-25.

Source: MedicineNet.com
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