title: Triton Hodge Test: Improved Protocol for Modified Hodge Test for Enhanced Detection of NDM and Other Carbapenemase Producers.
abstract: Accurate detection of carbapenemase-producing Gram-negative bacilli is of utmost importance for the control of nosocomial spread and the initiation of appropriate antimicrobial therapy. The modified Hodge test (MHT), a carbapenem inactivation assay, has shown poor sensitivity in detecting the worldwide spread of New Delhi metallo-β-lactamase (NDM). Recent studies demonstrated that NDM is a lipoprotein anchored to the outer membrane in Gram-negative bacteria, unlike all other known carbapenemases. Here we report that membrane anchoring of β-lactamases precludes detection of carbapenemase activity by the MHT. We also show that this limitation can be overcome by the addition of Triton X-100 during the test, which allows detection of NDM. We propose an improved version of the assay, called the Triton Hodge test (THT), which allows detection of membrane-bound carbapenemases with the addition of this nonionic surfactant. This test was challenged with a panel of 185 clinical isolates (145 carrying known carbapenemase-encoding genes and 40 carbapenemase nonproducers). The THT displayed test sensitivity of >90% against NDM-producing clinical isolates, while improving performance against other carbapenemases. Ertapenem provided the highest sensitivity (97 to 100%, depending on the type of carbapenemase), followed by meropenem (92.5 to 100%). Test specificity was not affected by the addition of Triton (87.5% and 92.5% with ertapenem and meropenem, respectively). This simple inexpensive test confers a large improvement to the sensitivity of the MHT for the detection of NDM and other carbapenemases.
authors.affiliation: Servicio Antimicrobianos, Laboratorio Nacional y Regional de Referencia en Antimicrobianos, Instituto Nacional de Enfermedades Infecciosas, ANLIS Dr. Carlos G. Malbrán, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Fernando
authors.initials: F
authors.lastname: Pasteran
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Santa Fé, Argentina.
authors.forename: Lisandro J
authors.initials: LJ
authors.lastname: Gonzalez
authors.affiliation: Servicio Antimicrobianos, Laboratorio Nacional y Regional de Referencia en Antimicrobianos, Instituto Nacional de Enfermedades Infecciosas, ANLIS Dr. Carlos G. Malbrán, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Albornoz
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Santa Fé, Argentina.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Bahr
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Santa Fé, Argentina.
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Vila
authors.affiliation: Servicio Antimicrobianos, Laboratorio Nacional y Regional de Referencia en Antimicrobianos, Instituto Nacional de Enfermedades Infecciosas, ANLIS Dr. Carlos G. Malbrán, Ciudad Autónoma de Buenos Aires, Argentina acorso@anlis.gov.ar.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Corso
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000032:analysis*; D003902:Detergents / Q000378:metabolism; D000077727:Ertapenem; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D000077731:Meropenem; D008826:Microbial Sensitivity Tests / Q000379:methods*; D017830:Octoxynol / Q000378:metabolism; D012680:Sensitivity and Specificity; D013845:Thienamycins / Q000494:pharmacology; D001618:beta-Lactamases / Q000032:analysis*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003902:Detergents; D013845:Thienamycins; D047090:beta-Lactams; D017830:Octoxynol; D001618:beta-Lactamases; C063912:carbapenemase; D000077731:Meropenem; D000077727:Ertapenem