Moxalactam is not more active on extended spectrum beta-lactamase (ESBL) producing bacteria than on non-ESBL producers Bhoj R Singh Division of Epidemiology, ICAR-Indian Veterinary Research Institute, Izatnagar, IndiaDear editorIn a recently published article1 moxalactam has been claimed to be very effective on extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae, concluding “MOX demonstrated excellent bactericidal effect, which is worthy of further exploration to serve as an alternative therapeutic agent against ESBL-producing Enterobacteriaceae”. Similar claims have also been made earlier.2 Out of interest we examined antimicrobial sensitivity data with reference to sensitivity to moxalactam, carbapenem resistant, and extended-spectrum β-lactamase (EBSL) and metallo-β-lactamase (MBL) production, among clinically important bacteria from the last 6 years (2011–2017), available from the Division of Epidemiology at Indian Veterinary Research Institute, Izatnagar. The analysis (Figure 1) revealed that conclusions drawn earlier1,2 on the basis of a study on a few strains may not be valid. My analysis revealed that of the 3,242 bacteria tested in our laboratory, using Clinical and Laboratory Standards Institute3 guidelines, 50.6% were identified as ESBL producers. Observations further revealed that moxalactam was certainly a more effective antibiotic on clinically important bacteria than most of the extended spectrum β-lactam antibiotics but no significant difference was detected between ESBL and non-ESBL producer bacteria with respect to their sensitivity to carbapenem (meropenem, imipenem and ertapenem), moxalactam and aztreonam. However, non-ESBL producing bacteria were more often positive for MBL production (p