In vivo modification of porin activity conferring antibiotic resistance to Enterobacter aerogenes.

Cephalosporins are widely used in chemotherapy of bacterial infections and resistance mechanisms seriously impair their antibacterial activity. Several resistant strains of Enterobacter aerogenes, a frequently isolated nosocomial pathogen, were analyzed. One isolate exhibited a strong modification of the porin antigenic pattern, especially with an immunological probe directed against an epitope located inside the pore lumen. A strong decrease of cefepime uptake was evidenced for this isolate, similarly to ones observed for porin-deficient strains: these kinetics show a serious alteration of the channel properties which may support cephalosporin resistance. This is the first E. aerogenes isolate using such adaptive response which defines an original enterobacterial answer to cephalosporin.