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The Molecular Characterization of Extended-Spectrum Beta-Lactamase (ESBL) and Carbapenem- Resistant Enterobacteriaceae (CRE) in Chicago Children, a two center study

Session: Poster Abstract Session: Pediatric - Bacterial Studies
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Posters
  • Logan_Molecular_ESBL_IDWeek_Poster_2014_Final.pdf (849.7 kB)
  • Background: The study objectives were to 1) determine the genetic basis of ESBL and CRE phenotypes in Enterobacteriaceae isolates from children in two medical centers; 2) determine genetic relatedness of dominant ESBL and CRE strains.

    Methods: We conducted a retrospective cohort study of clinical gram-negative isolates obtained from children ages 0-17 years hospitalized between 2011-12 at Rush and Lurie Children's Hospitals. PCR amplification of b-lactamase (blaTEM, blaSHV, blaCTX-M, blaKPC) genes was performed using established primers and amplified under thermocycling conditions.  Repetitive-sequence-based PCR (rep-PCR)  was used to assess the similarity of strains. Multilocus sequence typing (MLST) and DNA sequencing was performed on representative isolates from rep-PCR strain types for bacterial nomenclature and characterization. Plasmid DNA was extracted from select isolates and transformed into electrocompetent E. coli.

     

    Results: Ninety-two isolates exhibited ESBL and/or CRE phenotypes. The predominant organism was E. coli 55/92 (59.8%) and predominant genotype was blaCTX-M 37/92 (40.2%). Some isolates contained >1 bla gene.  Rep-PCR performed on the 55 E. coli revealed a diverse group with the most predominant strain accounting for 8/55 (14.5%) isolates (Figure 1). MLST was performed on select E. coli  (LC5, LC34, LC54) and K. pneumoniae (LC8 & LC77). LC34 represents the predominant E. coli  strain by rep-PCR and LC54 was selected as an unrelated strain type. LC34 was ST43 (ST131 in Achtman's MLST scheme). DNA sequencing confirmed the bla as CTX-M-15.  LC54 carrying blaTEM was identified as ST3. LC5 and LC77 carried blaKPC. ST types for LC5 and LC77 were ST29 and ST105 respectively and DNA sequencing confirmed presence of KPC-2 carbapenemase. DNA containing antibiotic resistance genes from LC5 (KPC-2) and LC34 (CTX-M-15) E. coli strains were successfully transferred suggesting plasmid-based origin.

    Conclusion: ESBL and CRE in children are diverse in origin. E. coli  carrying the bla CTX-M gene are thought to be primarily community-acquired , whereas dissemination of blaKPC is traditionally in the healthcare setting. Like in adults, CTX-M is spread in E.coli ST131.  In contrast, K.pneumoniae KPC bearing strains were non ST258, suggesting a different dissemination pattern than in adults.

     

     

     

     

     

     

    Figure 1. Relatedness of E. coli

     

    Latania K. Logan, MD1,2,3, Steve Marshall, MS4, Andrea M. Hujer, BS2,5, Xiaotian Zheng, MD PhD6 and Robert Bonomo, MD2,7, (1)Rush University Medical Center, Chicago, IL, (2)Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, (3)Rush Medical College, Chicago, IL, (4)Louis Stokes Cleveland VA Medical Center, Cleveland, OH, (5)Case Western Reserve University, Cleveland, OH, (6)Ann and Robert H. Lurie Children's Hospital of Chicago/Northwestern University, Chicago, IL, (7)Medicine, Pharmacology and Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH

    Disclosures:

    L. K. Logan, None

    S. Marshall, None

    A. M. Hujer, None

    X. Zheng, None

    R. Bonomo, None

    Findings in the abstracts are embargoed until 12:01 a.m. EDT, Oct. 8th with the exception of research findings presented at the IDWeek press conferences.

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