الفهرس 
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Abstract
Background: Multidrug-resistant tuberculosis (MDR-TB) is a major public health problem with ultimate concern in the developing countries. Effective management of MDR-TB counts on rapid and accurate diagnosis. Line probe assay (LPA) and GeneXpert MTB/RIF are two World Health Organization (WHO) approved probe based molecular drug susceptibility testing (DST) methods for rapid diagnosis of drug resistant tuberculosis. Both methods target the same 81 bp Rifampicin Resistance Determining Region for detection of Rifampicin resistance associated mutations using DNA probes. Aim: To detect prevalence of MDR-TB among naive and previously treated pulmonary TB patients from MOHP chest hospitals and chest medicine department (MUHs) with detection of mutations pattern and frequency in rpoB, katG and inhA genes in confirmed MDR-TB isolates, followed by comparison between molecular drug susceptibility testing methods in diagnosis of rifampicin resistance (GeneXpert versus Line probe assay). Setting: Genetic unit and MDICU at the Medical Microbiology and Immunology Department, Faculty of Medicine, Mansoura University. Results: The overall prevalence of MDR-TB among those diagnosed by PTB was estimated in this study by 8.6%, out of whom the primary resistance was estimated by 2% among new cases, while secondary resistance was 14.6% among previously treated patients. The most prominent genetic mutation conferring Rifampicin resistance was in codon S531 L of rpoB gene while among isoniazid resistant strains, S315T substitution mutation in the katG gene, C-15T substitution mutation in inhA gene were the recorded mutations. When DST was used as a gold standard, LPA had a better performance characteristic than GeneXpert. Conclusion: The use of the LPA in early detection of MDR-TB directly from the smear positive samples showed satisfactory diagnostic yield which may support its alternative use to conventional DST in daily clinical practice. •Key words: Line probe assay, GeneXpert, MDR-TB.