engleski

First report of carbapenem resistance in Klebsiella pneumoniae due to porin loss from Croatia

Objectives: Recently a first K. pneumoniae resistant to ertapenem and meropenem was isolated in Dubrava University Hospital, Zagreb, Ceroatia. The aim of the study was to explain the mechanisms of reduced susceptibility to carbapenems in ESBL producing K. pneumoniae that occured during therapy. Methods: Initially an ESBL producing K.pneumoniae was isolated from blood culture of the cardiac transplant patient. The patient was treated with meropenem twice in six weeks. Two weaks later K. pneumoniae with reduced suscepeptibility to carbapenems was isolated from anal swab. ESBL was detected by DDST. MIC was determined by broth microdilution according to CLSI. Modified Hodge Test(MHT) was used to screen for production of carbapenemases. MBL E-test was used to screen for production of metallo-beta-lactamases. The presence of blaSHV, blaTEM, blaCTX-M, blaACT-1, blaKPC, blaOXA-23, blaOXA-51, blaOXA-58, blaOXA-69 and blaVIM was determined by PCR. The genetic relatedness of the strains was investigated using PFGE. To study porin content of the strains, outer membrane proteins (OMPs) were extracted and separated by SDS-PAGE. Results: The initial isolate was susceptible to ertapenem (MIC 0.125 mg/L), meropenem (MIC 0.032 mg/l) and imipenem (MIC 0.25mg/l). The strain obtained after patient was treated with meropenem showed reduced carbapenem susceptibility: ertapenem MIC 32mg/l , meropenem MIC 16 mg/l, and imipenem MIC 8 mg/l. PFGE profile showed that strains are highly related. Both strains were shown to possess blaSHV and blaCTX-M genes by PCR. Sequencing of bla ESBL genes revealed the presence of CTX-M-15/28 and SHV-11 beta lactamases in both strains. MHT was negative in both strains. The PCR reactions with primers specific for ACT-1, KPC and oxacillinases were negative. Both isolates produced OMP-A like protein. Initial isolate expressed one single porin (Omp36) while second isolate did not produce any of the two major porins of K. pneumoniae (Omp35 or Omp36). Conclusion: K. pneumoniae with decreased carbapenem susceptibility was isolated from surveillance culture (anal swab) after prolonged meropenem therapy. Since no carbapenemases were produced by the strains it is likely to expect that carbapenem resistance was due to hyperproduction of CTX-M beta–lactamase combined with porin loss. This study highlights the need to establish an antimicrobial resistance survellance network for K.pneumoniae and to further monitor the trends and new

Klebsiella pneumoniae; porin loss; CTX-M-15 beta-lactamase

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