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James Wong, Laura C Huang, Jack Stringham, Jorge Maestre, Darlene Miller, Harry W Flynn; Prevalence of Accessory Gene Regulator (AGR) subtypes, Delta-Hemolysin (HLD) toxin, and correlation with Biofilm production among Staphylococcus epidermidis endophthalmitis isolates. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2863.
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To determine the presence of AGR subtypes and correlation with known coagulase negative staphylococcus virulence factors: biofilm production and delta toxin among Staphylococcus (S) epidermidis endophthalmitis isolates.
A multiplex polymerase chain reaction (PCR) assay with four primer sets was used to characterize AGR (1-4) types among S. epidermidis isolates, recovered from endophthalmitis. Separate PCR assays were run to detect the presence of the HLD gene loci. Biofilm production was evaluated qualitatively by staining test tubes inoculated with the isolates with crystal violet dye and grading the level of staining on a scale of 0 to 3 with 0 (non-adherent), 1 (weakly adherent), 2 (moderately adherent), and 3 (strongly adherent).
S. epidermidis isolates (n=33), were recovered from the anterior chamber (10) and vitreous (23) of endophthalmitis cases between 2010 and 2013. Three AGR subtypes, AGR1 (n=12, 36.4%), AGR2 (n=16, 48.5%), and AGR3 (n=3, 9.1%) were documented amongst isolates. The HLD toxin was documented in 32 (97%) samples. The mean biofilm grade of AGR subtypes were as follows: AGR1 was 2.33, AGR2 was 2.44, and AGR3 was 2.75. One-way analysis of variance indicated that there were no significant differences among the three groups F(2,29) = 0.57, p > 0.05.
To our knowledge, this is the first study determining AGR subtypes of S. epidermidis isolated from endophthalmitis. While isolates from infections in medical devices have been found to be AGR1 most commonly, the predominant profile for isolates among this group was AGR2 which may constitute a subtype unique to S. epidermidis endophthalmitis. All samples with AGR1 expressed HLD and were associated with a lower level of biofilm production than respective subtypes although this was not statistically significant. This may indicate that AGR, as a regulator of quorum sensing system, in particular AGR1, may downregulate biofilm production and upregulate toxin production.
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