beta-lactamases and outer membrane investigations in beta-lactam-resistantComamonas acidovorans strains

Imipenem-induced beta-lactamase (level of expression, specific activity and kinetic parameters (V-max and K-m) in response to nitrocefin) and outer me mbrane proteins (OMPs) (hydrophobicity, permeability and electrophoretic pa ttern) were characterized in, one beta-lactam sensitive (PAC-9), one resist ant (PAC-1) and two resistant laboratory mutants (PAC-9M, PAC-9M2) of Comam onas acidovorans strains. beta-lactamases from both mutant strains showed d ifferent V-max values compared to the parental strains. beta-lactam resista nce was found to be associated in PAC-1 with inducible beta-lactamase produ ction and OMP alteration by the appearance of a 102-KDa protein. Moreover, PAC-1 was less permeable to nitrocefin than PAC-9. These data indicate that C. acidovorans resistance to beta-lactam resulted from synergy between bet a-lactamase and OMP alterations. (C) 1999 Elsevier Science B.V. and Interna tional Society of Chemotherapy. All rights reserved.