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Nosocomial outbreak of CTX-M-15-producing E. coli in Norway
Umaer Naseer1, Olav B Natås, Bjørg C Haldorsen
1Reference Centre for Detection of Antimicrobial Resistance (K-res), Department of Microbiology and Infection Control, University Hospital of Northern Norway, Norway. Umaer.Naseer@fagmed.uit.no
Abstract:
Seven E. coli isolates expressing resistance to 3rd generation cephalosporins were recovered from blood (n=2), kidney and lung tissue (n=1), and urinary tract (n=4) samples from seven patients hospitalised or recently discharged from the Divisions of Geriatrics and Pulmonary Medicine, Central Hospital of Rogaland, between July and September 2004. All isolates expressed a typical ESBL-cefotaximase profile (cefotaxime MIC>ceftazidime MIC) with clavulanic acid synergy. A bla(CTX-M-15) genotype was confirmed in six strains that were coresistant to gentamicin, nitrofurantoin, trimethoprim-sulfamethoxazole and ciprofloxacin. A bla(CTX-M-3) genotype was detected in the last strain. XbaI-PFGE patterns of the six bla(CTX-M-15) isolates revealed a clonal relationship. Bla(CTX-M-15) strains were also positive for the ISEcp1-like insertion sequences that have been shown to be involved in the mobilization of bla(CTX-M.) Further analyses revealed two bla(CTX-M-15)-positive E. coli urinary isolates clonally related to the outbreak strain from two different patients at the same divisions in January and February 2004. These patients were later re-hospitalised and one had E. coli with an ESBL-cefotaximase profile in sputum and nasopharyngeal specimen during the outbreak period. Clinical evaluation suggests that the CTX-M-producing E. coli strains contributed to death in three patients due to delayed efficient antimicrobial therapy. The outbreak emphasises the epidemic potential of multiple-antibiotic-resistant CTX-M-15-producing E. coli also in a country with low antibiotic usage and low prevalence of antimicrobial resistance.
Insights
An outbreak of multidrug-resistant Escherichia coli (E. coli) producing extended-spectrum beta-lactamases (ESBLs) occurred in a hospital. The CTX-M-15-producing E. coli strains were linked to patient deaths, highlighting their epidemic potential.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Seven E. coli isolates exhibiting resistance to third-generation cephalosporins were identified in hospitalized patients.
- These isolates displayed an extended-spectrum beta-lactamase (ESBL) cefotaximase profile, indicating resistance mechanisms.
- The study occurred in a setting with historically low antibiotic usage and resistance prevalence.
Purpose of the Study:
- To characterize the genetic basis and epidemiological spread of ESBL-producing E. coli isolates.
- To investigate the clonal relationship and mobile genetic elements associated with antibiotic resistance.
- To assess the clinical impact and contribution of these resistant strains to patient outcomes.
Main Methods:
- Phenotypic characterization of antibiotic resistance, including minimum inhibitory concentration (MIC) testing.
- Genotypic analysis to identify beta-lactamase genes (blaCTX-M) and insertion sequences (ISEcp1).
- Pulsed-field gel electrophoresis (PFGE) for assessing clonal relatedness of isolates.
Main Results:
- Six out of seven E. coli isolates harbored the blaCTX-M-15 gene, showing co-resistance to multiple antibiotics.
- One isolate contained the blaCTX-M-3 gene. Clonal analysis revealed a close relationship among blaCTX-M-15 strains.
- The presence of ISEcp1-like insertion sequences suggested a role in the mobilization of blaCTX-M genes.
Conclusions:
- The blaCTX-M-15-producing E. coli strains demonstrated significant epidemic potential, even in low-resistance settings.
- These multidrug-resistant strains were associated with severe outcomes, including death, in patients with delayed treatment.
- The findings underscore the need for vigilant surveillance and control of ESBL-producing E. coli outbreaks.
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