PREVALENCE OF OUTER-MEMBRANE PORIN ALTERATION IN BETA-LACTAM-ANTIBIOTIC-RESISTANT ENTEROBACTER-AEROGENES

We evaluated the prevalence of impermeability as a mechanism associate d with resistance against beta-lactam antibiotics in members of the fa mily Enterobacteriaceae. During a 1-year period, 80 strains were selec ted from 3,110 routinely isolated strains according to their noticeabl e cross-resistance pattern to cephalosporins, They were tested for (i) outer membrane nonspecific porins involved in the entry of small hydr ophilic molecules; (ii) the MICs of cefepime, cefotaxime, imipenem, an d moxalactam; and (iii) beta-lactamase production, Immunological inves tigations using specific probes showed that 23 of 80 strains presented an alteration of the porin content, most of them expressing an additi onal resistance mechanism, The prevalence of this porin-deficient phen otype is especially high in Enterobacter aerogenes and concerns 6.4% o f the clinical isolates.