title: Resazurin Microtiter Assay for Clarithromycin Susceptibility Testing of Clinical Isolates of Mycobacterium abscessus Group.
abstract: BACKGROUND
  Mycobacterium abscessus group has heterogeneous susceptibility pattern among species. The species is most common cause of nosocomial infections. Macrolides minimum Inhibitory concentration (MIC) determination is essential for the treatment.
  
  
  METHODS
  Thirty-six strains were randomly selected for performing Resazurin Microtiter Assay (REMA) for clarithromycin testing in comparison to MIC test according to Clinical and Laboratory Standards Institute (2011) recommendation. REMA has been used for detection of drug resistance in M. tuberculosis. Extended incubation was performed to detect induced resistance.
  
  
  RESULTS
  Thirty microliters of resazurin (0.01%) was added after visually taking MIC reading. Resistance was observed in 11.1% of M. bolletti and 4.8% of M. abscessus strains; and induced resistance was detected in 77.8% and 95.2% of M. bolletti and M. abscessus strains, respectively. All strains of M. massiliense were susceptible. The samples presented same MIC value both by visual reading and through resazurin.
  
  
  CONCLUSIONS
  The present study showed 100% concordance between both readings, with REMA providing easier to read and report results benefit. This change in reading can also reflect on the MIC determination and report, improving the test.
authors.affiliation: Nucleo de Tuberculose e Micobacterioses, Instituto Adolfo Lutz, Sao Paulo, Brazil.
authors.forename: Natalia Fernandes
authors.initials: NF
authors.lastname: Garcia de Carvalho
authors.affiliation: Nucleo de Tuberculose e Micobacterioses, Instituto Adolfo Lutz, Sao Paulo, Brazil.
authors.forename: Daisy Nakamura
authors.initials: DN
authors.lastname: Sato
authors.affiliation: Laboratório de Micobacteriologia, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista "Júlio de Mesquita Filho,", Araraquara, Brazil.
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Pavan
authors.affiliation: Nucleo de Tuberculose e Micobacterioses, Instituto Adolfo Lutz, Sao Paulo, Brazil.
authors.forename: Lucilaine
authors.initials: L
authors.lastname: Ferrazoli
authors.affiliation: Nucleo de Tuberculose e Micobacterioses, Instituto Adolfo Lutz, Sao Paulo, Brazil. erchimara@yahoo.com.br.
authors.forename: Erica
authors.initials: E
authors.lastname: Chimara
mesh_terms: D017291:Clarithromycin / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009161:Mycobacterium / Q000302:isolation & purification*; D010078:Oxazines / Q000378:metabolism*; D014966:Xanthenes / Q000378:metabolism*
chemical_list: D010078:Oxazines; D014966:Xanthenes; C005843:resazurin; D017291:Clarithromycin
keywords: Mycobacterium abscessus; clarithromycin; resazurin microtiter assay; susceptibility testing