Antibiotic resistance has become the most importunate health issue and remains a major public health concern worldwide. Production of extended spectrum β-lactamases (ESBL) is one of the major causes of resistance to β-lactam antibiotics. Several in-vitro studies have demonstrated the significant impact of inoculum size on the effectiveness of β-lactam-β-lactamase inhibitor combination. Higher concentration of β-lactamase inhibitor (Sulbactam) will be needed to combat the increased production of ESBLs in infections with high inoculum. The primary objective of the present study is to evaluate Minimum Inhibitory Concentration (MICs) of ESBL producing Enterobacteriaceae, against Ceftriaxone alone and Ceftriaxone with Sulbactam combination (1:1 and 2:1) in presence of normal and higher inoculum of these bacteria. The secondary objective of the study is to demonstrate the in-vitro efficacy of Ceftriaxone-Sulbactam (CS) in presence of higher inoculum of bacteria.