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Title: Molecular characterisation of ESBLs from Klebsiella pneumoniae and Escherichia coli
Author: Dashti, Ali
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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In this study, one hundred-and-one unique patient isolates of K. pneumoniae (69) and E. coli (32), flagged as ESBL positive by the Vitek system (GNS 526 card) were collected. These strains were isolated from a variety of clinical specimens submitted to the clinical bacteriology laboratories of the Royal Infirmary of Edinburgh (RIE). Of the 101 strains tested, 15 E. coli were subsequently found to be ESBL-negative by E-test ESBL strips. On re-testing with Vitek using the (GNS 532 card which had superseded the GNS 526 card), 14 of these were found to be ESBL-negative despite originally flagging as ESBL-positive. The remaining 87 ESBL-producing strains were also subjected to the double disc diffusion (DDD) method for the detection of ESBLs. OF these, one was falsely negative for ESBL-production by E-test ESBL strips, and 7 false negative by the double disc diffusion method. The 87 isolates were tested for susceptibility to a wide range of antibiotics by both Vitek microdilution technique (NCCLS) and disc diffusion method (NCCLS). In addition, MICs of the isolates were obtained by agar dilution to aminoglycosides (gentamicin and tobramycin) and the quinolone, ciprofloxacin, and by E-test strips to cefotaxime and ceftazidime. To study the epidemiology of ESBL producing strains of K. pneumoniae and E. coli, all isolates were examined by Pulsed-field gel-electrophoresis (PFGE) analysis using the Xba1 restriction enzyme. K. pneumoniae demonstrated seven distinct clusters, each containing isolates with similar coefficients, which were identified among 62 isolates. A high level of genetic heterogeneity was found among the remaining 6 isolates, and one isolate was non-typeable by PFGE. PFGE demonstrated that 5 of the 18 E. coli were genetically related, 2 isolates belonged to one group, 8 isolates were genetically distinct and 3 were non-typeable.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available