Rapid acquisition of decreased carbapenem susceptibility in a strain of Klebsiella pneumoniae arising during meropenem therapy

J Findlay, A Hamouda, S J Dancer, S G B Amyes

Research output: Contribution to journalArticle (Academic Journal)peer-review

36 Citations (Scopus)


A strain of Klebsiella pneumoniae (K1) was isolated from a catheterized patient with a urinary tract infection. The patient was subsequently treated with meropenem, after which K. pneumoniae (K2) was once again isolated from the patient's urine. Susceptibility testing showed that strain K1 was fully susceptible to carbapenem antibiotics with the exception of ertapenem, to which it exhibited intermediate resistance, whilst K2 was resistant to ertapenem and meropenem. From pulsed-field gel electrophoresis profiling both strains exhibited identical banding patterns. Both contained CTX-M-15, OXA-1, SHV-1 and TEM-1 β-lactamase genes following PCR analyses. Outer membrane protein analysis demonstrated that K1 and K2 lacked an OMP of c. 40 kDa, with an additional OMP of c. 36 kDa missing from K2. Mutation studies showed that the K2 OMP phenotype could be selected by single-step carbapenem-resistant mutants of K1. Expression of transcriptional activator ramA and efflux pump component gene acrA were up-regulated in both strains by RT-PCR. Neither strain expressed ompK35, but ompK36 was found in both. Sequence analysis revealed gene sequences of ompK35, ompK36 and ramR in both strains; notably, ramR contained a mutation resulting in a premature stop codon. Transconjugation studies demonstrated transfer of a plasmid into E. coli encoding the CTX-M-15, TEM-1 and OXA-1 β-lactamases. We concluded that the carbapenem-resistant phenotype observed from this patient was attributable to a combination of CTX-M-15 β-lactamase, up-regulated efflux and altered outer membrane permeability, and that K2 arose from K1 as a direct result of meropenem therapy.

Original languageEnglish
Pages (from-to)140-6
Number of pages7
JournalClinical Microbiology and Infection
Issue number2
Publication statusPublished - Feb 2012


  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins
  • Catheter-Related Infections
  • Conjugation, Genetic
  • DNA, Bacterial
  • Electrophoresis, Gel, Pulsed-Field
  • Gene Expression Profiling
  • Gene Transfer, Horizontal
  • Genotype
  • Humans
  • Klebsiella Infections
  • Klebsiella pneumoniae
  • Microbial Sensitivity Tests
  • Molecular Typing
  • Molecular Weight
  • Mutation
  • Plasmids
  • Reverse Transcriptase Polymerase Chain Reaction
  • Selection, Genetic
  • Thienamycins
  • Urinary Tract Infections
  • Urine
  • beta-Lactam Resistance
  • beta-Lactams
  • Journal Article
  • Research Support, Non-U.S. Gov't


Dive into the research topics of 'Rapid acquisition of decreased carbapenem susceptibility in a strain of Klebsiella pneumoniae arising during meropenem therapy'. Together they form a unique fingerprint.

Cite this