title: Can ampicillin/sulbactam resistance in Acinetobacter baumannii be predicted accurately by disk diffusion?
abstract: The objective of this study was to compare the performance of disk diffusion and agar dilution for the determination of susceptibility to ampicillin/sulbactam (SAM), ceftazidime, cefepime, imipenem, meropenem, polymyxin B and tigecycline of 121 Acinetobacter baumannii clinical isolates. The antimicrobial susceptibility testing methods were performed as recommended by the Clinical and Laboratory Standards Institute (CLSI). For SAM, in addition the Etest method was performed according to the manufacturer's instructions. The error rates for the antimicrobial agents for 121 isolates tested were within the acceptable ranges established by the CLSI, with the exception of SAM and polymyxin B. For polymyxin B, there were 1.7% very major errors and for SAM there were 15% comparing disk diffusion with agar dilution. The very major error rate of SAM comparing the Etest with agar dilution was 10%. These high observed rates of very major error cast doubt on the disk diffusion and Etest techniques as appropriate methods for detecting resistance to SAM.
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Giselle Fukita
authors.initials: GF
authors.lastname: Viana
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Silvia Maria Dos Santos
authors.initials: SM
authors.lastname: Saalfeld
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Rafael Renato Brondani
authors.initials: RR
authors.lastname: Moreira
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Thatiany Cevallos
authors.initials: TC
authors.lastname: Menegucci
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Lourdes Botelho
authors.initials: LB
authors.lastname: Garcia
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil.
authors.forename: Celso Luiz
authors.initials: CL
authors.lastname: Cardoso
authors.affiliation: Departamento de Patologia, Análises Clínicas e Toxicológicas, Universidade Estadual de Londrina, Londrina, Paraná, Brazil.
authors.forename: Floristher Elaine Carrara
authors.initials: FE
authors.lastname: Marroni
authors.affiliation: Departamento de Ciências Básicas da Saúde, Universidade Estadual de Maringá, Maringá, Paraná, Brazil. Electronic address: mcbtognim@uem.br.
authors.forename: Maria Cristina Bronharo
authors.initials: MC
authors.lastname: Tognim
keywords: Acinetobacter baumannii; Agar dilution; Ampicillin/sulbactam; Disk diffusion; Etest