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S Rossetti, LP D'Alessandro; Genotypic Markers of Staphylococcus epidermidis Virulence Among Strains Isolated From Postoperative Endophthalmitis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4433.
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Purpose:To investigate the presence of genotypic markers of Staphylococcus epidermidis virulence, icaA, icaD and mecA among strains isolated from postoperative endophthalmitis and to compare them with conjunctival strains isolated from healthy eyes. Methods:The presence of icaA, icaD and mecA was determined in a collection of 27 Staphylococcus epidemidis strains isolated from postoperative endophthalmitis and in 20 strains from conjunctiva of healthy volunteers by a PCR method. For amplification of an internal control, we used universal primers targeting 16S rRNA gene. Slime-forming ability was tested on Congo red agar plates. Results:Twenty of 27 (74%) endophthalmitis isolates were positive for icaA and icaD genes. Twenty two of 27 (81%) endophthalmitis isolates were positive for mecA gene. Black colonies on Congo red agar were present in 18 of 27 (67%) isolates from endophthalmitis. Two of 20 (10%) S. epidermidis from conjunctiva of healthy eyes were positive for icaA, icaD and mecA genes. Black colonies on Congo red agar were also present in 2 of 20 isolates from conjunctiva of healthy eyes. Conclusion:Genotypic markers of virulence icaA, icaD and mecA appear to be important factors in the induction of S. epidermidis postoperative endophthalmitis. They were present in most of our endophthalmitis strains (74-81%). S. epidermidis from conjunctiva of healthy eyes are not usually biofilm producers and don’t have pathogenic factors. The difference between both groups was strongly significative (p<0.0001). S. epidermidis capable to produce postoperative endophthalmitis are mostly biofilm producers and more pathogenic and resistant than the normal ocular flora of healthy eyes.
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