<p>Molecular epidemiology and resistance profiles among healthcare- and community-associated <em>Staphylococcus aureus</em> keratitis isolates</p>

Abstract

Purpose To characterize the molecular, epidemiological, and resistance profiles of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) keratitis isolates. Patients and methods We used a combination of standard microbiological techniques and DNA microarray analysis to characterize the molecular and antibiotic resistance profiles of 75 Staphylococcus aureus keratitis isolates collected over an 11-year period (2006–2016). Results Two major USA clonal complexes (CC), CC5 (n=30, 40%) and CC8 (n=28, 37.3%), accounted for 77.3% of the collected S. aureus isolates. USA100, traditionally healthcare associated (n=18/47, 38.3%), and USA300, traditionally community associated (n=12/47, 25.5%), were the dominant MRSA strains. Four (22.2%) of the USA100 MRSA isolates were recovered from patients with no prior healthcare exposure. Eleven (91.7%) of the USA300 isolates were recovered from patients with documented healthcare risk factors. MSSA isolates were polyclonal (n=13). Ninety-three percent of MSSA infections were of healthcare origin. Thirty-seven of 61 (60.6%) healthcare- and 11 of 14 (78.6%) community-associated strains were resistant to three or more antibiotic classes. Sixty-eight percent (n=51) of isolates harbored three of more resistance determinants (genes). The Panton-Valentine Leucocidin gene was detected in 11 (14.7%) of the study isolates. The majority (72.7%) of the strains were members of the USA300 MRSA clone. Conclusion Clonal complexes CC5 and CC8 were the most frequent clones detected among both the MSSA and the MRSA keratitis isolates. USA100 and USA300 clones were the dominant MRSA genotypes. The USA300 MRSA clone has become a leading cause of healthcare-associated keratitis in South Florida. The USA100 MRSA clone has emerged as an increasing cause of community-associated corneal infections in our outpatient population. This shifting epidemiology coupled with the increasing prevalence of multidrug resistance among both MSSA and MRSA keratitis is a cause of concern.

Genomics of Staphylococcus aureus ocular isolates

“…This aligns nearly identically with the recent report of 56 ocular isolates collected from Massachusetts Eye and Ear Infirmary that demonstrated 23.2% ST5, 16% ST8 and 11% ST30 [13]. Similarly, a set of 75 S. aureus keratitis isolates collected from the University of Miami, Bascom Palmer Eye Institute, included 40% isolates of clonal complex (CC) 5 (ST5 is classified within CC5), and 37.3% of CC8 (ST8 is classified within CC8) [16]. Interestingly, only one isolate from this study set was identified in clonal complex 30.…”

“…Much is still unknown regarding the mechanisms by which S. aureus can establish and maintain infections in the eye, however, initial studies have begun to identify specific strain types as well as virulence factors that may be particularly important in ocular disease. For example, multilocus sequence typing (MLST), which compares the genetic sequences of seven housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi, and yqiL) to identify sequence types (STs), has revealed ST5, ST8, ST15, ST30, ST59, and ST772 as common among specific S. aureus ocular strain sets [13][14][15][16]. Additionally, studies to assess the prevalence of S. aureus virulence factors among ocular isolates such as Panton-Valentine Leukocidin (pvl), Enterotoxin E (sea) or Leukocidin E (lukE) have demonstrated that while pvl and lukE are found in the majority of sampled ocular strains, sea may be less common [16,17].…”

“…For example, multilocus sequence typing (MLST), which compares the genetic sequences of seven housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi, and yqiL) to identify sequence types (STs), has revealed ST5, ST8, ST15, ST30, ST59, and ST772 as common among specific S. aureus ocular strain sets [13][14][15][16]. Additionally, studies to assess the prevalence of S. aureus virulence factors among ocular isolates such as Panton-Valentine Leukocidin (pvl), Enterotoxin E (sea) or Leukocidin E (lukE) have demonstrated that while pvl and lukE are found in the majority of sampled ocular strains, sea may be less common [16,17]. While this initial work has provided insight into the genetic characteristics of ocular S. aureus clinical isolates, they have largely been limited to small sample sizes and a handful of virulence factors.…”

An Eye on Staphylococcus aureus Toxins: Roles in Ocular Damage and Inflammation

“…However, in addition to PVL binding to retinal ganglion cells, the toxin also co-localized to horizontal cells which did not express C5a receptor, and there was no significant increase in IL-6 as compared to the control explants. Peterson et al [101] recently reported that the PVL gene was detected in only 14.7% of S. aureus keratitis isolates in their study, so it is unclear how clinically relevant this toxin is to ocular disease.…”

Stability Evaluation of Extemporaneously Compounded Vancomycin Ophthalmic Drops: Effect of Solvents and Storage Conditions

“…The acquisition of the mecA or mecC genes, which lead to alternative penicillin-binding proteins, account for the most common mechanism of resistance that results in the methicillin-resistant phenotype [ 6 , 7 , 8 , 9 ]. Although historically considered a hospital-acquired infection, MRSA clones are increasingly being encountered among community infections [ 10 , 11 , 12 ]. MRSA is known to cause a variety of ocular infections, including keratitis [ 13 , 14 , 15 ].…”