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Jack Stringham, James Wong, Laura C Huang, Jorge Maestre, Darlene Miller, Harry W Flynn; Endophthalmitis caused by Staphylococcus epidermidis: SCCmec Types and Prevalence of the Panton-Valentine Leukocidin (PVL) Toxin. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2865.
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To evaluate the molecular profile among Staphylococcus (S) epidermidis isolates causing endophthalmitis and to correlate these findings with potential virulence tendencies.
Multiplex polymerase chain reaction (PCR) assays were run to characterize the type (I-IV) and subtypes (of type IV a-h) of staphylococcal cassette chromosome mec (SCCmec), a mobile genetic element known to carry the mecA gene that confers methicillin resistance. PCR was also used to confirm the presence of the mecA gene. A separate PCR was done to detect the presence of the PVL gene.
Isolates originated from intraocular fluid of patients with endophthalmitis collected from 2010-2013. All (n=33) of the isolates were mecA positive. SCCmec type IV 76% (25) was the most the most common profile. Type IV subtypes included: IVc 48% (16), SCCmec type IVa 18% (6), and SCCmec type IVh 9% (3). Less than 10% of the isolates were SCCmec type III 6% (2) or SCCmec type I 3% (1). SCCmec type II was not detected among this group. Four cases were untypable. PVL necrotizing toxin was not identified in this series.
The predominate SCCmec type among S. epidermidis is type IV. The genetic makeup of our small consecutive case series suggests that S. epidermidis causing endophthalmitis may be difficult to treat due to high methicillin resistance conferred by the presence of the mecA gene. Additionally the lack of the PVL toxin indicates that S. epidermidis may cause a more mild infection than PVL positive S. aureus causing endophthalmitis that has been previously documented. Future study involves clinical correlation with the molecular profiles.
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