Resistance to cefepime and cefpirome due to a 4-amino-acid deletion in the chromosome-encoded AmpC beta-lactamase of a Serratia marcescens clinical isolate.
A multiresistant Serratia marcescens strain, HD, isolated from a patient with a urinary tract infection, was resistant to amino-, carboxy-, and ureidopenicillins, ceftazidime, and cefepime and was susceptible to cefotaxime and ceftriaxone, according to the guidelines of the NCCLS. No synergy was found between expanded-spectrum cephalosporins and clavulanic acid, according to the double-disk synergy test. The bla(AmpC) gene of the strain was amplified by PCR and cloned into Escherichia coli DH10B, giving rise to high-level resistance to ceftazidime, cefepime, and cefpirome. Sequencing analysis revealed that the bla(AmpC) gene from S. marcescens HD had a 12-nucleotide deletion compared to the bla(AmpC) gene from reference strain S. marcescens S3, leading to a 4-amino-acid deletion located in the H-10 helix of the beta-lactamase. Kinetic analysis showed that this enzyme significantly hydrolyzed ceftazidime, cefepime, and cefpirome. This work underlined that resistance to the latest expanded-spectrum cephalosporins may be mediated by structurally modified AmpC-type beta-lactamases.
Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Paris-Sud, Université Paris XI, 94275 Le Kremlin-Bicêtre, France.
Hedi
H
Mammeri
Laurent
L
Poirel
Pascal
P
Bemer
Henri
H
Drugeon
Patrice
P
Nordmann
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D000077723:Cefepime; D018550:Cephalosporin Resistance / Q000235:genetics; D002510:Cephalosporinase / Q000235:genetics / Q000378:metabolism; D002511:Cephalosporins / Q000494:pharmacology*; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D006868:Hydrolysis; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics / Q000502:physiology*; D010957:Plasmids / Q000235:genetics; D017384:Sequence Deletion; D016868:Serratia Infections / Q000382:microbiology*; D012706:Serratia marcescens / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*; D000097572:Cefpirome
D001426:Bacterial Proteins; D000077723:Cefepime; D002510:Cephalosporinase; D002511:Cephalosporins; D001618:beta-Lactamases; D000097572:Cefpirome; C048795:AmpC beta-lactamases