Analysis of the Degradation of Broad-Spectrum Cephalosporins by OXA-48-Producing Using MALDI-TOF MS.

The objective of the study was to evaluate the activity of OXA-48 against different broad-spectrum cephalosporins and to identify the reaction products by MALDI-TOF MS. The action of OXA-48 on cefotaxime, ceftazidime, and ceftriaxone was assessed by this method, using an J53 transconjugant carrying only the 62 Kb IncL plasmid containing the gene, and the same strain without any plasmid was included as a negative control. In addition, a collection of 17 clinical OXA-48-producing , which were susceptible to broad-spectrum cephalosporins, was evaluated. MALDI-TOF MS-based analysis of the transconjugant carrying the -harboring plasmid, and also the clinical isolates, showed degradation of cefotaxime into two inactive compounds-decarboxylated and deacetylated cefotaxime (370 Da) and deacetyl cefotaxime (~414 Da), both with the hydrolyzed beta-lactam ring. Reaction products were not obtained when the experiment was performed with ceftriaxone or ceftazidime. From a clinical point of view, our study supports the idea that the efficacy of cefotaxime against OXA-48-producing is doubtful, in contrast to ceftazidime and ceftriaxone which could be valid choices for treating infections caused by these bacteria. However, further clinical studies confirming this hypothesis are required.