Comparative MIC evaluation of a generic ceftriaxone by broth microdilution on clinically relevant isolates from an academic hospital complex in South Africa

We evaluated the in vitro microbiological efficacy of a generic ceftriaxone product against several clinically significant organisms collected from sterile sites. The minimum inhibitory concentration (MIC) of each was determined simultaneously with the reference and the generic ceftriaxone product. Comparative analysis of MICs between the two products for each isolate was performed using both categorical (interpretive) agreement and essential (actual MIC value) agreement. A total of 260 isolates were tested. Overall, there was categorical agreement of 98.9% and essential agreement of 95.8%. The categorical agreement for all isolates (96.7 - 100%) accorded with international standards, as no very major errors were seen and the major error rate was less than 3%. Of the 90 isolates of E. coli (40), Klebsiella spp. (40) and Salmonella spp. (10), 87.6% had an MIC less than or equal to 0.12 mg/l. The generic ceftriaxone product showed equivalent efficacy by MIC determination to the reference formulation. Ceftriaxone remains a viable and useful antimicrobial agent against a variety of clinically relevant organisms in our setting