Extensively drug resistant TB (XTB) in South Africa
Polly Clayden, HIV i-Base
Tuberculosis has long been neglected because it is treatable and predominantly affects the poor. Very concerning data on extensively drug resistant TB was presented in a study from South Africa.
In an oral late breaker, Neel Ghandi presented results from a study to determine the extent of multi drug resistant (MDR) and extensively drug resistant (XDR) among patients presenting with TB in in KwaZulu Natal. 
MDR TB is defined as having resistance to isoniazid and rifampicin. XDR TB is defined as having resistance to all first and second line TB drugs (isoniazid, rifampicin, ethambutol, streptomycin, kanamycin and cipropfloxacin) and was described in a recent CDC and WHO report (see articles later in this issue of HTB). Only 347 XDR TB isolates have been found worldwide. 
This was a cross-sectional study of patients suspected to have active TB at a rural district hospital. Isolates were collected for mycobacterial culture from January 2005 to March 2006.
The investigators found that out of a group of 1539 patients, 995 (68%) were culture negative and 544 (35%) patients were culture positive for TB. Of these, 323 (69%) were not resistant to both isoniazid and rifampicin and 221 (41%) were resistant (ie had MDR TB). Of these 53 (24% of MDR isolates, 10% of all positive cultures) had resistance to all first and second line drugs tested (ie had XDR TB).
The XDR TB patients were a median of 35 years (range 20-75 years), 25 (49%) were women; 42 (79%) were sputum smear positive and 11 (21%) were sputum smear negative. Of the group, 26 (51%) had no prior TB treatment; 14 (28%) had cured or completed treatment and 7 (14%) had defaulted or failed treatment.
The investigators suggested that the majority of these patients were newly infected with drug resistant TB strains, and had not developed drug resistance on treatment. They reported that 64% had been hospitalised for any cause prior to the onset of XDR TB. The group of patients included two healthcare workers who died with confirmed XDR TB (and four others with suspected XDR TB). Nonsocomial transmission in hospitals is probable Dr Ghandi said, but transmission in the community is also possible as 36% of XDR TB patients had no prior hospitalisations.
They also reported 26/30 (87%) XDR TB patients were infected with a genetically similar strain. 52 of 53 (98%) XDR TB patients have died; the median survival after sputum collection was 16 days (range: 2-210).
All 44 (88%) XDR TB patients who had been tested for HIV, were HIV positive and 15(34%) were on antiretroviral therapy.
The investigators wrote: The convergence of the TB/HIV epidemic with MDR and XDR TB in resource poor settings is a deadly threat to gains in survival achieved by TB DOTS and ARV therapy.
Gandhi NR, Moll A, Pawinski R et al. High prevalence and mortality from extensively-drug resistant (XDR) TB in TB/HIV coinfected patients in rural South Africa. XVI International AIDS Conference, Toronto, Canada.13 – 18 August 2006. Abstract THLB0210.