Purchase this article with an account.
Jack Stringham, Darlene Miller, Laura C. Huang, Harry W Flynn; Distribution and Group Specificity of the Accessory Gene Regulon (agr) (Quorum Sensing Network) among Staphylococcus (S.) Epidermidis Endophthalmitis Isolates. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5503.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The accessory gene regulon (agr) in S. epidermidis regulates virulent factors such as biofilm and toxin expression. Pathology and host immune response have been linked to specific agr genotypes; agr1 (septicemia, colonization), agr2(biomaterial adherence, multidrug resistance), agr3 (tissue destruction/biopsies). We test the hypothesis that S. epidermidis strains recovered from different endophthalmitis presentations are correlated with unique agr quorum sensing genotypes.
A multiplex PCR assay was used to determine the diversity of the agr gene for 79 S. epidermidis isolates recovered from intraocular fluids of patients with endophthalmitis collected during 2010-2013. Group specificity/genotype was correlated with clinical disease and nonsusceptibility rates/MIC values for methicillin, moxifloxacin and vancomycin. Clinical presentations (n=64) included 41 cases associated with post-operative endophthalmitis and 23 non-operative endophthalmitis cases. Nonsusceptibility rates were determined by the Vitek2 and or E tests.
All three agr genotypes were documented among the clinical S. epidermidis isolates. AGR type II (agrII) was the most frequent 48.4% (31/64) followed by agrI -40.6% (26/64) and agrIII 10.9% (7/64). Type II was the most common group associated with post-operative cases (43.9% with the highest rates identified in post cataract cases (18.8%). AgrII was also the most common group recovered from non-operative cases (52.2%, highest rate for post injections cases). Methicillin and multidrug resistance (MRSE) isolates were more frequently associated with group II (52.1%, 22/43 vs 36.1%, 13/36). Group III (agrII) was more often recovered from MSSE isolates (22.2%, 8/36 vs 4.6%, 2/43). Moxifloxacin values ranged from 0.026-32 ug/ml. MIC90 for both agrI and agrII was 4 (resistant). All tested agrIII (n=9) strains were susceptible with MICs less than 1. MIC values for vancomycin ranged from 0.125-4 ug/ml, with an MIC90 of 4 (susceptible) for all agr groups.
The predominant agr genotype among S. epidermidis strains from both post-operative and non-operative endophthalmitis cases was agr group II. This group was more likely to be methicillin and moxifloxacin resistance and associated with higher vancomycin MICs suggestive of tolerance.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only