Susceptibility Pattern and Epidemiology of Mycobacterium tuberculosis in United Emirati Hospital

Human tuberculosis (TB) has re-emerged at an alarming rate as one of the deadliest contagious diseases; not only in the developing world, but also in the developed countries. Its re-emergence indicates failure to control its transmission. What causes part of the alarm is the growing number of isolates displaying resistance to the first line drugs used in its control. The very high volume of travel to the United Arab Emirates (UAE) is yet another reason for concern over the spread of the disease. This study reports on the pattern of multiple drug (MDR) resistance exhibited by Mycobacterium tuberculosis (MTB) isolates from a major hospital in the UAE.

All pulmonary and extrapulmonary tuberculosis patients with positive culture results from January 2001 to December 2008 were included in the study. Cultures were performed at the mycobacteriology laboratory of the Emirati Hospital, Abu Dhabi, UAE, using the conventional Lewes-Johnson media. M. tuberculosis was isolated by standard procedures. M. tuberculosis complex was identified by conventional biochemical tests. Anti-mycobacterial sensitivity testing was done by the disk method as described by Wayne & Krasnow.

From 2002 to 2008, 43 nonrepetitive culture-positive cases were identified. The resistance rates of M. tuberculosis to tested first-line agents were as follows: isoniazid, 34.5%; pyrazinamide, 34.8%; rifampin, 32.5%; streptomycin, 25.6%; and ethambutol, 20.9%. The resistance rate to isoniazid, rifampin and pyrazinamide was 7%; to isoniazid, rifampin and streptomycin was 2.3%; and to isoniazid, rifampin, streptomycin and pyrazinamide was 2.3%. The resistance rate to all the five agents together was 4.6%.

This study is the first in the UAE to report such high levels of resistance to anti-TB drugs; 27.7% for anti-tuberculosis Drugs such as isoniazid and pyrazinamide are of great significance to achieve proper treatment in M. tuberculosis infections in future. Indeed, isoniazid and rifampicin are important components of any regimen for the treatment of drug susceptible TB.