Evaluation of four phenotypic methods to detect plasmid-mediated AmpC β-lactamases in clinical isolates

  1. Gude, M.J. 1
  2. Seral, C. 2
  3. Sáenz, Y. 3
  4. González-Domínguez, M. 1
  5. Torres, C. 4
  6. Castillo, F.J. 2
  1. 1 Hospital Clínico Universitario Lozano Blesa
    info

    Hospital Clínico Universitario Lozano Blesa

    Zaragoza, España

    ROR https://ror.org/03fyv3102

  2. 2 Universidad de Zaragoza
    info

    Universidad de Zaragoza

    Zaragoza, España

    ROR https://ror.org/012a91z28

  3. 3 Centro de Investigación Biomédica de La Rioja
    info

    Centro de Investigación Biomédica de La Rioja

    Logroño, España

    ROR https://ror.org/03vfjzd38

  4. 4 Universidad de La Rioja
    info

    Universidad de La Rioja

    Logroño, España

    ROR https://ror.org/0553yr311

Mostrar afiliaciones +
Revista:
European Journal of Clinical Microbiology and Infectious Diseases

ISSN: 0934-9723

Año de publicación: 2012

Volumen: 31

Número: 8

Páginas: 2037-2043

Tipo: Artículo

DOI: 10.1007/S10096-011-1537-Y SCOPUS: 2-s2.0-84866412819 WoS: WOS:000306952700046 GOOGLE SCHOLAR

Otras publicaciones en: European Journal of Clinical Microbiology and Infectious Diseases

Resumen

Four phenotypic methods (three dimensional test, AmpC test, cloxacillin synergy test and cefotetan/cefotetancloxacillin E-test) to detect plasmid-mediated AmpC β- lactamases (pAmpC) were compared in 125 clinical Enterobacteriaceae isolates with AmpC profile: 74 E. coli (blaCMY-2: 70; blaDHA-1: 4), five K. pneumoniae (blaCMY-2: 2; blaDHA-1: 3), six P. mirabilis (blaCMY-2: 6) and 40 negative isolates for pAmpC β-lactamases. All evaluated methods showed a good sensitivity (>95%) but low values of specificity (<60%) in E. coli, explained by an increase of AmpC expression caused by chromosomal ampC promoter/ attenuator mutations (-42, -18, -1, +58, predominantly). The cefotetan/cefotetan- cloxacillin or cloxacillin synergy test may be advocated as phenotypic screening test, and the AmpC test as confirmatory test for detection of pAmpC in isolates that lack or minimally express chromosomally encoded AmpC β-lactamases. In the case of E. coli, the phenotypic evaluated tests were not able to differentiate between chromosomal ampC overexpression or acquisition of plasmid-encoded ampC genes. © Springer-Verlag 2012.