title: Inducible and constitutive clindamycin resistance in Staphylococcus aureus in a northeastern Indian tertiary care hospital.
abstract: BACKGROUND
  Staphylococcus aureus is one of the most common pyogenic bacteria. They are notorious for developing prompt resistance to newer antimicrobials. With increasing incidence of methicillin-resistant S. aureus (MRSA) isolates, the treatment options are also becoming limited. Clindamycin is an excellent drug for skin and soft tissue infections, but resistance mediated by the inducible phenotype (iMLS(B)) leads to in vivo therapeutic failure even though there may be in vitro susceptibility. The double disk approximation test (D-test) can reliably detect the presence of such isolates. This study was aimed to detect and report the prevalence of the iMLS(B) phenotype in NEIGRIHMS, a tertiary care center in Northeast India.
  
  
  METHODS
  A total of 243 consecutive isolates were subjected to routine identification tests followed by antimicrobial sensitivity testing. Erythromycin-resistant isolates were tested for inducible resistance phenotype by the D-test.
  
  
  RESULTS
  Among strains tested, 95 (39%) were erythromycin resistant. Twenty-six (10.7%) isolates were D-test positive (iMLS(B) phenotype), 41 (16.88%) were constitutively resistant (cMLS(B) phenotype), and 28 isolates (11.52%) were found to be negative by D-test. The incidence of both inducible and constitutive phenotypes was higher in MRSA isolates compared to methicillin-sensitive S. aureus (MSSA) isolates.
  
  
  CONCLUSIONS
  This study revealed a moderate prevalence of the inducible clindamycin phenotype in the staphylococcal isolates tested. Clinical microbiology laboratories in areas of high MRSA prevalence should consider performing the D-test routinely. This will help prevent prescription of drug(s) whose therapeutic efficacy is doubtful.
authors.affiliation: North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong, India. dramitbanik@gmail.com.
authors.forename: Amit
authors.initials: A
authors.lastname: Banik
authors.forename: Annie Bakorlin
authors.initials: AB
authors.lastname: Khyriem
authors.forename: Jeetendra
authors.initials: J
authors.lastname: Gurung
authors.forename: Valarie Wihiwot
authors.initials: VW
authors.lastname: Lyngdoh
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002981:Clindamycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D006801:Humans; D007194:India / Q000453:epidemiology; D010641:Phenotype; D015995:Prevalence; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D062606:Tertiary Care Centers; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D002981:Clindamycin; D004917:Erythromycin