Sirus Amini1, Sven Hoffner2, Mohammad Reza Allahyar Torkaman3, Gholamreza Hamzehloo3, Mohammad Javad Nasiri4, Mahshid Salehi5, Golnar Sami Kashkooli6, Mohammad Sadegh Shahraki7, Maryam Mohsenpoor8, Saman Soleimanpour9, Raha Mir9. 1. Regional Tuberculosis Reference Laboratory, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: sirusamini@gmail.com. 2. Swedish Institute for Infectious Disease Control, Stockholm, Sweden. 3. Regional Tuberculosis Reference Laboratory, Tehran University of Medical Sciences, Tehran, Iran. 4. Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 5. Regional Tuberculosis Reference Laboratory, Isfahan University of Medical Sciences, Isfahan, Iran. 6. Tuberculosis Reference Laboratory, Shiraz University of Medical Sciences, Shiraz, Iran. 7. Regional Tuberculosis Reference Laboratory, Zahedan University of Medical Sciences, Zahedan, Iran. 8. Tuberculosis Reference Laboratory, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. 9. Antimicrobial Resistance Research Center, Bu-Ali Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran.
Abstract
INTRODUCTION: Conventional indirect drug susceptibility testing (DST) of Mycobacterium tuberculosis with solid media is inexpensive and reliable, but time-consuming. This study aimed to evaluate direct DST for testing sputum samples without culture to significantly reduce the time required to detect multidrug-resistant tuberculosis (MDR-TB). METHODS: Direct and indirect DST of isoniazid (INH), rifampicin (RIF) and ethambutol (EMB) were performed on 334 sputum smear-positive specimens. RESULTS: There was full agreement between the results obtained from direct testing and after isolation of the bacteria by culture. Thus, the sensitivity and specificity were observed to be 100% for all three tested drugs when compared with indirect DST. In comparison with indirect DST, none of the samples with the direct method took >25days to report the DST (between 15-25days with a mean detection time of 20 days). CONCLUSIONS: Direct DST on solid media was shown to give reliable results at a much earlier stage than conventional phenotypic DST. The direct method was found to be more rapid, more accurate and simpler. In addition, it reduced the handling of pathogenic bacteria and thus reduced the bio hazards related to conventional DST.
INTRODUCTION: Conventional indirect drug susceptibility testing (DST) of Mycobacterium tuberculosis with solid media is inexpensive and reliable, but time-consuming. This study aimed to evaluate direct DST for testing sputum samples without culture to significantly reduce the time required to detect multidrug-resistant tuberculosis (MDR-TB). METHODS: Direct and indirect DST of isoniazid (INH), rifampicin (RIF) and ethambutol (EMB) were performed on 334 sputum smear-positive specimens. RESULTS: There was full agreement between the results obtained from direct testing and after isolation of the bacteria by culture. Thus, the sensitivity and specificity were observed to be 100% for all three tested drugs when compared with indirect DST. In comparison with indirect DST, none of the samples with the direct method took >25days to report the DST (between 15-25days with a mean detection time of 20 days). CONCLUSIONS: Direct DST on solid media was shown to give reliable results at a much earlier stage than conventional phenotypic DST. The direct method was found to be more rapid, more accurate and simpler. In addition, it reduced the handling of pathogenic bacteria and thus reduced the bio hazards related to conventional DST.
Authors: F Bahraminia; M Zangiabadian; M J Nasiri; M Fattahi; M Goudarzi; R Ranjbar; A A Imani Fooladi Journal: New Microbes New Infect Date: 2021-06-23