Increasing Drug Resistance in XDR TB | CDC EID

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Volume 17, Number 3–March 2011
Dispatch
Increasing Drug Resistance in Extensively Drug-Resistant Tuberculosis, South Africa
N. Sarita Shah, Jessica Richardson, Prashini Moodley, Salona Moodley, Palav Babaria, Melissa Ramtahal, Scott K. Heysell, Xuan Li, Anthony P. Moll, Gerald Friedland, A. Willem Sturm, and Neel R. Gandhi


Author affiliations: Tugela Ferry Care and Research Collaboration, Tugela Ferry, South Africa (N.S. Shah, J. Richardson, P. Babaria, S.K. Heysell, A.P. Moll, G. Friedland, N.R. Gandhi); Albert Einstein College of Medicine, Bronx, New York, USA (N.S. Shah, J. Richardson, X. Li, N.R. Gandhi); Montefiore Medical Center, Bronx (N.S. Shah, J. Richardson, X. Li, N.R. Gandhi); Nelson R. Mandela School of Medicine, Durban, South Africa (P. Moodley, S. Moodley, M. Ramtahal, A.W. Sturm); Yale University, New Haven, Connecticut, USA (P. Babaria, G. Friedland); and Philanjalo Care Center, Tugela Ferry (A.P. Moll)

Suggested citation for this article

Abstract
We expanded second-line tuberculosis (TB) drug susceptibility testing for extensively drug-resistant Mycobacterium tuberculosis isolates from South Africa. Of 19 patients with extensively drug-resistant TB identified during February 2008–April 2009, 13 (68%) had isolates resistant to all 8 drugs tested. This resistance leaves no effective treatment with available drugs in South Africa.

Extensively drug-resistant tuberculosis (XDR TB) was first reported in 2005 and has been identified worldwide (1,2). XDR TB is associated with poor treatment outcomes (3), especially among persons co-infected with HIV (4,5). XDR TB strains are created when multidrug-resistant TB (MDR TB) is inadequately treated, which enables amplification of second-line drug resistance (6,7). Inadequate treatment for XDR TB may result in additional resistance, severely limiting options for effective treatment.

Drug-susceptibility testing (DST) for first-line and second-line TB drugs is essential for developing effective MDR TB and XDR TB treatment regimens (8,9). However, DST requires laboratory facilities that are unavailable in most settings with high incidence of TB. In the last global report of drug resistance, only one third of countries conducted routine DST on suspected cases of TB; the remaining countries restricted testing to high-risk patients (2). Thus, most high-incidence settings use standardized MDR TB or XDR TB treatment regimens based on epidemiologic data from periodic drug-resistance surveys. Because the epidemiology of drug-resistant TB is changing rapidly (10), successful use of standardized regimens depends on accurate population-level drug-resistance data.

In 2005, a large HIV-associated XDR TB epidemic was detected in Tugela Ferry, South Africa (5). Continuous, routine drug resistance surveillance for all suspected TB cases has since been implemented in Tugela Ferry and >500 XDR TB cases have been diagnosed; >90% of patients are coinfected with HIV. Most early XDR TB isolates from Tugela Ferry were resistant to 4 or 5 drugs (isoniazid, rifampin, ofloxacin, and kanamycin, plus ethambutol or streptomycin) (4). XDR TB isolates have become resistant to an increasing number of drugs, such that by 2007, >90% were resistant to all 6 first-line and second-line drugs tested (Figure 1) (4).

DST for other second-line drugs (in addition to ofloxacin and kanamycin) is not routinely performed in South Africa. However, the standardized XDR TB treatment regimen includes second-line drugs for which drug resistance data are lacking. Thus, we sought to further characterize second-line TB drug resistance among XDR TB isolates in Tugela Ferry by expanding DST to include capreomycin and ethionamide.

full-text:
Increasing Drug Resistance in XDR TB | CDC EID


Suggested Citation for this Article
Shah NS, Richardson J, Moodley P, Moodley S, Babaria P, Ramatahal M, et al. Increasing drug resistance in extensively drug-resistant tuberculosis, South Africa. Emerg Infect Dis [serial on the Internet]. 2011 Mar [date cited]. http://www.cdc.gov/EID/content/17/3/510.htm


DOI: 10.3201/eid1703.101363


Comments to the Authors
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N. Sarita Shah, Departments of Medicine and Epidemiology and Population Health, Albert Einstein College of Medicine, 111 E 210 St, Bronx, NY 10467, USA; email: saritashah2@gmail.com