title: Laboratory tests in the detection of extended spectrum beta-lactamase production: National Committee for Clinical Laboratory Standards (NCCLS) screening test, the E-test, the double disk confirmatory test, and cefoxitin susceptibility testing.
abstract: Extended spectrum beta-lactamase (ESBL) production by Klebsiella sp. and E. coli is an emerging problem. In this study, 107 clinical isolates (53 E. coli, 47 K. pneumoniae and 7 K. oxytoca) screened as ESBL producers by the NCCLS disk diffusion procedure were submitted to a double disk confirmatory test (DDT) and to the E-test double strip for confirmation of ESBL production by demonstration of clavulanic acid inhibition effect (CAIE). Only 72/107 (67%) of the isolates were confirmed as ESBL producers by DDT, with diverse results among species. By the E-test, 58/107 (54%) isolates were confirmed as ESBL producers, and 18/107 (17%) were not determinable. Susceptibility to cefoxitin was found in 57/68 (83%) of strains that did not show CAIE. ESBL detection remains a controversial issue and clinical laboratories are in need of a simple and effective way to recognize strains with this kind of resistance.
authors.affiliation: Federal Faculty of Medical Sciences, Foundation of Porto Alegre, RS 90050-170, Brazil. pedroaze@fffcmpa.tche.br
authors.forename: Pedro A
authors.initials: PA
authors.lastname: d'Azevedo
authors.forename: Ana Lúcia S
authors.initials: AL
authors.lastname: Gonçalves
authors.forename: Maiara I
authors.initials: MI
authors.lastname: Musskopf
authors.forename: Carina G
authors.initials: CG
authors.lastname: Ramos
authors.forename: Cícero A G
authors.initials: CA
authors.lastname: Dias
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002440:Cefoxitin / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D041121:Klebsiella oxytoca / Q000187:drug effects / Q000201:enzymology*; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology*; D008826:Microbial Sensitivity Tests / Q000379:methods; D010641:Phenotype; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D002440:Cefoxitin; D001618:beta-Lactamases