Beta-lactam resistance in Aeromonas spp. caused by inducible beta-lactamases active against penicillins, cephalosporins, and carbapenems.
Use of cefoperazone in a patient with Aeromonas caviae in the respiratory tract selected a mutant that constitutively produced beta-lactamase. This mutant, in contrast to its parental strain with an inducible beta-lactamase, showed enhanced resistance to newer cephalosporins and aztreonam. This observation suggested that species of Aeromonas, like those of other genera with inducible beta-lactamases, may pose therapeutic problems associated with the rapid development of multiple beta-lactam resistance. Thus, a study was designed to identify the beta-lactamases in 12 strains representing four species of Aeromonas and assess their role in drug resistance. Eleven strains possessed inducible beta-lactamases. One strain showed no detectable activity. An analysis of substrate and inhibitor profiles, isoelectric points, and beta-lactam susceptibility patterns revealed the presence of at least four distinguishable inducible beta-lactamases. These enzymes were involved in the resistance of strains within the genus to penicillins, cephalosporins, aztreonam, and imipenem but not cefoxitin. Unlike most other organisms with inducible beta-lactamases, all four strains of A. caviae, one of four strains of A. sobria, and one of three strains of A. hydrophila possessed two distinct inducible beta-lactamases. Furthermore, substrate and inhibitor profiles revealed that many of these Aeromonas beta-lactamases were distinct from inducible enzymes that have been characterized in other genera of gram-negative bacteria.
Bakken
J S
JS
Department of Medical Microbiology, Creighton University School of Medicine, Omaha, Nebraska 68178.
Sanders
C C
CC
Clark
R B
RB
Hori
M
M
D000333:Aeromonas / Q000187:drug effects*; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001398:Aztreonam / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D002511:Cephalosporins / Q000378:metabolism; D004352:Drug Resistance, Microbial; D004790:Enzyme Induction; D006801:Humans; D015378:Imipenem / Q000378:metabolism; D007525:Isoelectric Focusing; D008297:Male; D010406:Penicillins / Q000378:metabolism; D001618:beta-Lactamases / Q000096:biosynthesis*
D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D002511:Cephalosporins; D010406:Penicillins; D015378:Imipenem; D001618:beta-Lactamases; D001398:Aztreonam