title: In-vitro emergence of beta-lactam-resistant variants of Pseudomonas aeruginosa.
abstract: The frequency with which resistant variants could be found in Pseudomonas aeruginosa ATCC 27853 during growth in media with and without antibiotics was determined for ticarcillin, piperacillin, cefotaxime, latamoxef, cefoperazone, ceftriaxone, ceftazidime, aztreonam and imipenem. The resistance frequency was highest for ceftriaxone, cefotaxime, cefoperazone and piperacillin (up to 2 X 10(-4)) and lowest for ticarcillin, latamoxef, ceftazidime, aztreonam and imipenem (less than 10(-8)). The resistant variants showed cross-resistance to all of the beta-lactam antibiotics tested with the exception of imipenem. The MIC profiles of all variants were similar regardless of which antibiotic the cultures had been exposed to previously. Although all resistant variants produced and excreted cephalosporinases, increased resistance was demonstrated to both cephalosporinase-susceptible and cephalosporinase-stable beta-lactam antibiotics.
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000494:pharmacology*; D001711:Biotransformation; D004352:Drug Resistance, Microbial; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams