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Timothy Morris, Christine Sanfilippo, Christine Hesje, Matthew MacGilvray, Wolfgang Haas; Prevalence and characteristics of MRSA from clinical conjunctivitis trials versus ocular surveillance studies. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2886. doi: https://doi.org/.
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Methicillin-resistant Staphylococcus aureus (MRSA) strains can cause severe infections of the eye. Typical hospital-acquired (HA) MRSA strains contain the SCCmec II resistance cassette and are multi-drug resistant, while community-acquired (CA) MRSA isolates generally possess the SCCmec IV cassette and are usually considered to be more virulent. Both subgroups also tend to be genetically distinct. This study determined the proportion of HA and CA MRSA among isolates from clinical conjunctivitis trials compared to those from ocular surveillance studies.
27 MRSA isolates from three conjunctivitis trials conducted between 2004-2007, and 298 MRSA isolates from various types of ocular infections from the 2009-2011 ARMOR surveillance studies were characterized and compared. Antibiotic susceptibility testing against oxacillin (OXA), ciprofloxacin (CIP), and azithromycin (AZI) was performed according to current CLSI guidelines. PCR amplification and DNA sequence analysis were used to determine the spa and SCCmec types and ascertain the presence of the Panton-Valentine Leukocidin (PVL) toxin.
Of the ocular MRSA isolates studied here, both the conjunctivitis trial isolates and the surveillance study isolates contained similar ratios of strains that met the criteria for HA-MRSA (51.9% and 48.1%, respectively) and for CA-MRSA (46.0% and 50.7%, respectively).Overall, the conjunctivitis trial isolates showed a higher diversity in genetic lineages (spa types) compared to the surveillance study isolates, which were dominated by spa types t002 and t008. Twelve (44.4%) different spa types were identified among the 27 conjunctivitis trial isolates, compared to 52 (17.4%) different spa types identified among the 298 surveillance study isolates (3 of which were novel and not found in the Ridom SpaServer database).
The data from analysis of conjunctivitis trial and surveillance study MRSA isolates indicate that both HA and CA strains are fully capable of infecting the eye. The results further suggest that, while the surveillance study MRSA includes a higher percentage of isolates that are of concern due to drug resistance and virulence, the conjunctivitis trial group also contains a notable number of these isolates.
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