title: Collateral damage of flomoxef therapy: in vivo development of porin deficiency and acquisition of blaDHA-1 leading to ertapenem resistance in a clinical isolate of Klebsiella pneumoniae producing CTX-M-3 and SHV-5 beta-lactamases.
abstract: OBJECTIVE
  The study aimed to characterize the genetic basis of flomoxef and collateral ertapenem resistance in a clinical isolate of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) after flomoxef exposure.
  
  
  METHODS
  Four ESBL-KP isolates (Lkp11-14) were recovered sequentially from four episodes of bacteraemia in an elderly patient. Laboratory investigations included genotyping by PFGE, resistance gene analysis by PCR and sequencing, and outer membrane protein analysis by SDS-PAGE. Plasmid analysis by DNA-DNA hybridization, electroporation and conjugation was also performed.
  
  
  RESULTS
  Lkp14 was recovered after 21 days of flomoxef therapy. It demonstrated an indistinguishable PFGE pattern when compared with those produced by Lkp11-13. However, resistance to both flomoxef and ertapenem emerged in Lkp14. Molecular characterization revealed that, in addition to the pre-existing ESBL production (CTX-M-3 and SHV-5) and OmpK35 deficiency found in Lkp11-13, Lkp14 had acquired an extra plasmid-mediated AmpC beta-lactamase gene (blaDHA-1) and failed to express OmpK36, because of insertional inactivation by an insertion sequence IS5. Other resistance mechanisms, such as production of carbapenem-hydrolysing enzymes or expression of chromosomal efflux, were apparently not involved. Conjugational transfer of the plasmid-mediated blaDHA-1 gene into Lkp11 resulted in a significant increase in the MICs of cephamycins and beta-lactamase inhibitors, but not in those of carbapenems.
  
  
  CONCLUSIONS
  Lkp14 was apparently derived from the previously flomoxef-susceptible isolates, Lkp11-13. After flomoxef exposure, the in vivo acquisition of the plasmid-mediated blaDHA-1 gene has led to flomoxef resistance in Lkp14, and the concomitant depletion of OmpK36 expression has resulted in a collateral effect of ertapenem resistance and diminished susceptibilities to imipenem and meropenem.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, 123 Ta-Pei Road, Niao-Sung, Kaohsiung 833, Taiwan.
authors.forename: Chen-Hsiang
authors.initials: CH
authors.lastname: Lee
authors.forename: Chishih
authors.initials: C
authors.lastname: Chu
authors.forename: Jien-Wei
authors.initials: JW
authors.lastname: Liu
authors.forename: Yi-Shung
authors.initials: YS
authors.lastname: Chen
authors.forename: Chiung-Jung
authors.initials: CJ
authors.lastname: Chiu
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Su
mesh_terms: D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001426:Bacterial Proteins / Q000235:genetics; D002511:Cephalosporins / Q000627:therapeutic use*; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D018274:Electroporation; D000077727:Ertapenem; D005260:Female; D005838:Genotype; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D007710:Klebsiella Infections / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D018272:Porins / Q000172:deficiency*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013845:Thienamycins / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; D018272:Porins; D013845:Thienamycins; D047090:beta-Lactams; D015378:Imipenem; C417271:beta-lactamase CTX-M-3; C117193:beta-lactamase SHV-5; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C494147:beta-lactamase DHA-1, Salmonella; D000077731:Meropenem; D000077727:Ertapenem; C045693:flomoxef