title: Inducible Clindamycin Resistance in Staphylococcus aureus Isolated from Clinical Samples.
abstract: BACKGROUND
  The resistance to antimicrobial agents among Staphylococci is an increasing problem. This has led to renewed interest in the usage of Macrolide-Lincosamide-Streptogramin B (MLS(B)) antibiotics to treat Staphylococcus aureus (S. aureus) infections. The resistance to macrolide can be mediated by msr A gene coding for efflux mechanism or via erm gene encoding for enzymes that confer inducible or constitutive resistance to MLS(B)antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D test on a routine basis.
  
  
  METHODS
  One hundred and ninety S. aureus isolates were subjected to routine antibiotic susceptibility testing including oxacillin (1 µg) and cefoxitin (30 µg) by modified Kirby Bauer disc diffusion method. Inducible resistance to clindamycin in S. aureus was tested by 'D test' as per CLSI guidelines.
  
  
  RESULTS
  Twenty (10%) isolates showed inducible clindamycin resistance, 18 (9%) showed constitutive resistance while remaining 16 (8%) showed MS phenotype. Inducible resistance and constitutive resistance were found to be higher in MRSA as compared to MSSA (20%, 16% and 6%, 6%, respectively).
  
  
  CONCLUSIONS
  Clindamycin is kept as a reserve drug and is usually advocated in severe MRSA infections depending upon the antimicrobial susceptibility results. This study showed that D test should be used as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in Staphylococci for the optimum treatment of patients.
authors.affiliation: Department of Microbiology, Yenepoya Medical College, Deralakatte, Mangalore, Karnataka, India.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Prabhu
authors.forename: Sunil
authors.initials: S
authors.lastname: Rao
authors.forename: Venkatakrishna
authors.initials: V
authors.lastname: Rao