Background: Confirmation of a pathogen's susceptibility to an antimicrobial is essential to achieve the best treatment approach. Antibiotic Susceptibility Tests (AST) includes manual and automated techniques, Minimal Inhibitory Concentration (MIC) which require 3 to 5 days for AST results; the Direct Manual AST (DMAST) method shortens this result time window, without decreasing the specificity or sensitivity of current AST approaches. Time is crucial in day-to-day clinical practice, especially in bacterial infections which can lead to numerous pathological consequences and antibiotic misuse and resistance. Methods & Materials: DMAST modifies the CLSI (Clinical and Laboratory Standards Institute) disc diffusion tests using urine samples. In this protocol, DMAST was used in urine samples, following the direct smear process on a Mueller Hinton Agar Petri dish; this allows obtaining results in only 8 to 18 hours after sample collection. Each DMAST sample was analyzed after 8 hours and 18 hours incubation at 37˚C. In order, to compare the reliability of this new technique DMAST with MIC system, the same sample was processed as the micro dilution MIC method, it was used the Phoenix 100 equipment; the results were analyzed in 3 to 8 days. This study was done in 62 samples per group ages ranged from: 9 months to 92 years old, 47 female and 15 male cases, were analyzed in each AST inhibition zone in described time window. Results: Overall, agreement between the two methods was: DMAST with Gram negative bacteria in urine colony counts >100.000 UCF/mL compared with the MIC system. Statistically parameters: Sensitivity 97.9%, Specificity 81.8%, PPV (Positive Predictive Value) 99.5% and NPV (Negative Predictive Value) 44.4% and showed no statistical differences, probability of > 0.09 between DMAST and MIC (p>0.09). Conclusion: Daily clinical practice requires optimal diagnostic methods decreasing the use of wide spectrum antibiotics and health costs. DMAST reliably presents results in an earlier time window (saving around 64-120 hours for diagnosis) than MIC procedures. The present study suggests the initial DMAST can give sensitivity results in 8-18 hours for urgent cases and late MIC for confirmatory purposes.