title: Molecular & phenotypic characterization of Staphylococcus epidermidis in implant related infections.
abstract: OBJECTIVE
  The discrimination between the Staphylococcus epidermidis colonizing the deep seated indwelling devices and those which are mere commensals has always been a challenge for the clinical microbiologist. This study was aimed to characterize the S. epidermidis isolates obtained from device related infection for their phenotypic and molecular markers of virulence and to see whether these markers can be used to differentiate the pathogenic S. epidermidis from the commensals.
  
  
  METHODS
  Fifty five S. epidermidis isolates from various device related infections such as endophthalmitis following intra-ocular lens (IOL) implantation, intravascular (IV) catheter related sepsis and orthopaedic implant infections, were studied for slime production, biotyping, antibiotic sensitivity; and mec A and ica positivity by the recommended procedures.
  
  
  RESULTS
  Twenty three (41.8%) isolates were multi-drug resistant, 26 (65.2%) were slime producers, 30 (54.5%) were adherent, 23 (41.8%) possessed the intercellular adhesin (ica) gene, and 28 (50.9%) harboured the mec A gene. Biotypes I and III were the commonest, most members of which were multi- drug resistant. Twenty two (73.3%) of the 30 adherent bacteria were slime producers as opposed to only 4 (16%) of the 25 non-adherent bacteria (P<0.001). A vast majority i.e. 21 (91.3%) of the 23 ica positive organisms were adherent to artificial surfaces in contrast to only 9 (28.1%) of the 32 non-ica positive organisms (P<0.001). Twenty (86.9%) of the 23 ica positive bacteria were slime producers, as opposed to only 6 (18.7%) of the 32 ica negative bacteria (P<0.001). Of the 23 multi-drug resistant isolates, 19 (82.6%) carried the mec A gene.
  
  
  CONCLUSIONS
  The present findings showed that ica AB and mec A were the two important virulence markers of S. epidermidis in implant infections and slime was responsible for the sessile mode of attachment on the devices.
authors.affiliation: Department of Ocular Microbiology, Dr R.P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Sujata
authors.initials: S
authors.lastname: Prasad
authors.forename: N
authors.initials: N
authors.lastname: Nayak
authors.forename: G
authors.initials: G
authors.lastname: Satpathy
authors.forename: H L
authors.initials: HL
authors.lastname: Nag
authors.forename: P
authors.initials: P
authors.lastname: Venkatesh
authors.forename: S
authors.initials: S
authors.lastname: Ramakrishnan
authors.forename: Supriyo
authors.initials: S
authors.lastname: Ghose
authors.forename: T C
authors.initials: TC
authors.lastname: Nag
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D019736:Prostheses and Implants / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000235:genetics / Q000302:isolation & purification*; D014774:Virulence