title: Phenotypic and genotypic characterization of Rhodococcus equi isolated from sputum.
abstract: BACKGROUND
  Rhodococcus equi is an opportunistic pathogen, causing rhodococcosis, a condition that can be confused with tuberculosis. Often, without identifying M. tuberculosis, physicians initiate empiric treatment for tuberculosis. R. equi and M. tuberculosis have different susceptibility to drugs. Identification of R. equi is based on a variety of phenotypic, chromatographic, and genotypic characteristics.
  
  
  OBJECTIVE
  This study aimed to characterize bacterial isolates from sputum samples suggestive of R. equi.
  
  
  METHODS
  The phenotypic identification included biochemical assays; thin-layer chromatography (TLC) and polymerase chain reaction (PCR) were used for genotypic identification.
  
  
  RESULTS
  Among 78 Gram-positive and partially acid-fast bacilli isolated from the sputum of tuberculosis-suspected patients, 51 were phenotypically and genotypically characterized as R. equi based on literature data. Mycolic acid analysis showed that all suspected R. equi had compounds with a retention factor (R(f)) between 0.4-0.5. Genotypic characterization indicated the presence of the choE gene 959bp fragments in 51 isolates CAMP test positive. Twenty-two CAMP test negative isolates were negative for the choE gene. Five isolates presumptively identified as R. equi, CAMP test positive, were choE gene negative, and probably belonged to other bacterial species.
  
  
  CONCLUSIONS
  The phenotypic and molecular techniques used constitute a good methodological tool to identify R. equi.
authors.affiliation: Instituto Adolfo Lutz, Núcleo de Ciências Biomédicas/Centro de Laboratório Regional (IAL-NCB/CLR-VI), Ribeirão Preto, SP, Brazil. pdsilva@ial.sp.gov.br
authors.forename: Paulo da
authors.initials: Pd
authors.lastname: Silva
authors.forename: Adolfo Carlos Barreto
authors.initials: AC
authors.lastname: Santos
authors.forename: Daisy Nakamura
authors.initials: DN
authors.lastname: Sato
authors.forename: Jaqueline Otero
authors.initials: JO
authors.lastname: Silva
authors.forename: Marta Inês Cazentini
authors.initials: MI
authors.lastname: Medeiros
authors.forename: Ana Maria Machado
authors.initials: AM
authors.lastname: Carneiro
authors.forename: Sergio Roberto de Andrade
authors.initials: SR
authors.lastname: Leite
authors.forename: Clarice Queico Fujimura
authors.initials: CQ
authors.lastname: Leite
mesh_terms: D002855:Chromatography, Thin Layer; D004269:DNA, Bacterial / Q000032:analysis; D003937:Diagnosis, Differential; D005838:Genotype; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis / Q000382:microbiology*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D016929:Rhodococcus equi / Q000235:genetics* / Q000302:isolation & purification; D013183:Sputum / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial