A Study on the Prevalence of IS256 Insertion Sequence and Biofilm Formation in Staphylococcus Epidermidis Isolated from Healthy Human Skin

Introduction: Biofilm formation mediated by a polysaccharide intercellular adhesin (PIA) is considered a major pathogenic factor of staphylococcus epidermidis. PIA production is regulated by icaADBC operon. IS256 causes phase variation of biofilm formation by inactivation of ica operon. This study was aimed at investigating the prevalence of IS256 and biofilm formation in staphylococcus epidermidis isolated from healthy human skin.   Materials & Methods: 91 isolates of staphylococcus epidermidis were collected from the surface of healthy human skin. All the isolates were examined in terms of ability of biofilm formation by Microtiter plate assay. PCR technique with specific primers was used to determine the presence of IS2556. Additionally, all the isolates containing  IS256 were examined in term of aminoglycoside resistance, fluoro- quinolones, macrolides, and glycopeptides by disk diffusion method. Data were analyzed using SPSS software.   Findings: Out of the 91 isolates, only 8 (8/79%) cases contained IS256. The microtiter plate assay results showed that attachment abilities 58 (63/73%) lacked, 6 (6/6%) were weak, 14 (15/38%) were moderate and 13 (14/29%) were strong biofilm producers. The isolates containing IS256, 6 (75%) lacked, 1 (12/5%) was weak, and 1(12/5%) was moderate biofilm producer. The  isolates containing IS256, 3 (37/5%) were resistant to gentamicin, 2 (25%) to amikacin, 2 (25%) to streptomycin, 1(12/5%) to ciprofloxacin, 1(12/5%) to ofloxacin and 4 (50%)  were resistant to erythromycin, but no resistance to vancomycin was observed.   Discussion & Conclusions: The results demonstrated no relation  between the IS256 and biofilm formation. Not mutch resistance to aminoglycosides was observed in isolates containing IS256 hich. This is quite incompatible with the so-called role of IS256 in forming aminoglycoside resistanc