title: Evaluation of constitutive and inducible resistance to clindamycin in clinical samples of Staphylococcus aureus from a tertiary hospital.
abstract: BACKGROUND
  Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become common in hospitals and the community environment, and this wide resistance has limited patient treatment. Clindamycin (CL) represents an important alternative therapy for infections caused by S. aureus. Antimicrobial susceptibility testing using standard methods may not detect inducible CL resistance. This study was performed to detect the phenotypes of resistance to macrolides-lincosamides-streptogramin B (MLSB) antibiotics, including CL, in clinical samples of S. aureus from patients at a tertiary hospital in Santa Maria, State of Rio Grande do Sul, Brazil.
  
  
  METHODS
  One hundred and forty clinical isolates were submitted to the disk diffusion induction test (D-test) with an erythromycin (ER) disk positioned at a distance of 20mm from a CL disk. The results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI).
  
  
  RESULTS
  In this study, 29 (20.7%) of the 140 S. aureus samples were resistant to methicillin (MRSA), and 111 (79.3%) were susceptible to methicillin (MSSA). The constitutive resistance phenotype (cMLSB) was observed in 20 (14.3%) MRSA samples and in 5 (3.6%) MSSA samples, whereas the inducible resistance phenotype (iMLSB) was observed in 3 (2.1%) MRSA samples and in 8 (5.8%) MSSA samples.
  
  
  CONCLUSIONS
  The D-test is essential for detecting the iMLSB phenotype because the early identification of this phenotype allows clinicians to choose an appropriate treatment for patients. Furthermore, this test is simple, easy to perform and inexpensive.
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Angelita
authors.initials: A
authors.lastname: Bottega
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Mônica de Abreu
authors.initials: Mde A
authors.lastname: Rodrigues
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Fernanda Aguirre
authors.initials: FA
authors.lastname: Carvalho
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Tatiana Feyh
authors.initials: TF
authors.lastname: Wagner
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Isabel Agne Souza
authors.initials: IA
authors.lastname: Leal
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Silvana Oliveira dos
authors.initials: SO
authors.lastname: Santos
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Roberta Filipini
authors.initials: RF
authors.lastname: Rampelotto
authors.affiliation: Departamento de Análises Clínicas e Toxicológicas, Universidade Federal de Santa Maria, Santa Maria, RS, BRAZIL.
authors.forename: Rosmari
authors.initials: R
authors.lastname: Hörner
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002981:Clindamycin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D062606:Tertiary Care Centers
chemical_list: D000900:Anti-Bacterial Agents; D002981:Clindamycin; D004917:Erythromycin