Tuberculosis (TB) is one of the most important challenges for the health care system of any state. In 2016, 9 million new cases were registered globally, the Republic of Moldova ranking among 30 countries with the biggest burden of multidrug-resistance tuberculosis (MDRTB). One of the most relevant control actions represents the early case detection, especially of MDR-TB. The precocious treatment is considered the most efficient tool for interrupting the epidemiological chain of disease transmission. The cultural methods remain the golden standard for TB diagnosis, despite low sensibility and long duration of cultivation. Conventional microscopy for identification of acid-fast-bacilli is the first step in the microbiological investigation. Its low sensibility endangers the epidemiological situation. In 2011 the WHO established conditional recommendations to use Xpert MTB/RIF assay in testing adults, children and persons with HIV suspected for TB, or for testing the non-respiratory specimens targeting the diagnosis of extrapulmonary TB. It is an in-vitro diagnostic device, owned by Cepheid Company and is a semi-nested, quantitative, real-time polymerase chain reaction for the DNA detection of all Mycobacterium tuberculosis (MBT) complex species and rifampicin resistance mutations of the rpoB gene. The system automates the sample processing, nucleic amplification and detection of the target sequences of rpoB gene. Any biological specimen can be processed considering that it requires the minimum of 2 ml of sample volume. The high sensitivity (97,3%) of the Xpert MTB/RIF among culture positive specimens and 99.5% in smear positive patients contributes to earlier detection and precocious treatment according to the rifampicin resistant results. The aim of the research was to establish the impact of the microbiological methods in diagnosis delay and treatment outcome in patients with MDR-TB. Material and methods: It was performed a selective, descriptive and retrospective study conducted according to a linear model, carried out on 226 new cases of pulmonary MDRTB investigated according to the National Clinical Protocol. Were used laboratory examinations: general blood and urine analysis, chest X-ray, sputum microscopy for acid fast bacilli, conventional microbiological investigations (smear microscopy, Lowenstein – Jensen culture, BACTEC assay) and innovative platform of the Xpert MTB/RIF test. Patients were distributed in a study group (1st group) 85 cases with MDR-TB detected through Xpert MTB/RIF test and the control group (2nd group) 141 cases treated for MDR-TB, according to the results of the drug susceptibility test on conventional microbiological methods (Lowenstein – Jensen culture either BACTEC assay). Results and discussions. Assessing the groups according to the sex distribution was established the predominance of men in all groups. So, in the 1st group were 61 (71.7%) and women 24 (28.3%) with a male/female ratio = 2.5/1 and in the 2nd group 106 (75.1%) were men and 35 (24.8%), ratio=3/1. Detection particularities established the predominance of the passive case-finding 68 (80.1%) in the 1st group and 106 (75.2%) patients in the 2nd group. Assessing the diagnosis delay, it was identified that each fourth patient in both groups were diagnosed in more than three months after the disease onset. The early diagnosis till 30 days after the disease onset was established in each fifth patient in the 1st group 7 (8.4%). Pulmonary infiltrative TB was diagnosed in the most of the patients in both groups: 79 (93.1%) in the 1st group and 132 (93.6%) in the 2nd group. Severe forms were in a limited number 6 (7.1%) in the 1st group and 7 (4.9%) in the 2nd group. Treatment success was in a higher rate in the 1st group 59 (69.4%) vs. the 2nd group 84 (59.6%). Were loss to follow-up more frequently patients from the 2nd group 21 (14.9%) vs. 9 (10,6%). Died in a similar rate 22 (15.6%) in the 2nd group compared and 12 (14.1%) in the 1st group. Conlcusions: Xpert MTB/Rif assay diminish the rate of late detected forms of pulmonary TB, adapts the treatment according to the resistance to Rifampicin and improves disease outcome.