Mutations in the ampC promoter of Escherichia coli isolates resistant to oxyiminocephalosporins without extended spectrum beta-lactamase production.
Escherichia coli strains showing an increased resistance to oxyiminocephalosporins without an extended spectrum beta-lactamase production have been screened for mutations in their ampC beta-lactamase gene promoter. Mutations were found by direct sequencing of seven promoters at positions -42, -32 (box -35), -18, -1, +5, +24 (attenuator), +31 (attenuator) and +58. By using rapid and simple methods, three of these mutations (-42, -32 and +24), which could enhance transcription, were searched in 37 resistant and 25 sensitive isolates. The -42 mutation was present in 33 of the 37 promoters from the resistant isolates. The -32 and +24 mutations were present only in three and two promoters, respectively, and they were combined in the most resistant strain of the study. The +24 mutation was detected in another strain associated with a 1-bp insertion between the -35 and -10 conserved sequences. None of these mutations was detected in the ampC beta-lactamase from the sensitive isolates.
Caroff
N
N
Laboratoire de Bactériologie-Virologie, Faculté de Pharmacie, Nantes, France. interepi@chu-nantes.fr
Espaze
E
E
Bérard
I
I
Richet
H
H
Reynaud
A
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins; D001483:Base Sequence; D002440:Cefoxitin / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology; D002513:Cephamycins / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D002513:Cephamycins; D002440:Cefoxitin; C048795:AmpC beta-lactamases; D001618:beta-Lactamases