Two Klebsiella pneumoniae strains selected according to their high cross-resistance pattern to cephalosporins were characterized by (i) outer membrane protein content such as OmpA or nonspecific porins, (ii) MICs of various cephalosporins and unrelated antibiotics, (iii) beta-lactamase production, and (iv) active efflux of fluoroquinolones. An association of porin deficiency and beta-lactamase production induced a noticeable cephalosporin resistance. In addition to these mechanisms, the presence of an active efflux participating in high-level fluoroquinolone resistance was identified in one strain. The decrease of antibiotic uptake associated with efflux explains the Klebsiella adaptation against the drugs present in the environment.
Copyright 2000 Academic Press.