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2015 OMIG Abstract 7

Molecular Epidemiology of Ocular Staphylococcus aureus Infections
Paulo J. M. Bispo, Jenna Wurster and Michael S. Gilmore.
Massachusetts Eye and Ear Infirmary, Harvard Medical School

Purpose: Staphylococcus aureus is a common cause of severe and difficult-to-treat ocular infections because of its virulence and antibiotic resistance. In this study, we aimed to determine the genetic relatedness of methicillin-susceptible (MSSA) and –resistant S. aureus (MRSA) recovered in 2014 from eye and periocular infections. Methods: A total of 71 ocular S. aureus isolates, 30 MRSA and 41 MSSA, were subjected to multilocus sequence typing. MRSA isolates were typed for SCCmec and screened for the presence of the panton-valentine leukocidin (PVL). Antibiotic resistance was also determined. Results: MSSA isolates fell into 21 different sequence types, most of which were associated to clonal complex CC30 (12.2%) and to somewhat related CCs including CC1 (9,7%), CC5 (9,7%), CC15 (9,7%), CC72 (9,7%), CC25 (7.3%) and CC8 (7.3%). Strains belonging to CC398 (7.3%), widely found in livestock-associated infections, were also isolated. SCCmec type IV was predominant (70%) among MRSA, followed by SCCmec type II (30%). SCCmec type IV isolates were frequently PVL-positive (76.2%) and mainly associated with CC8, while type II isolates were PVL-negative and grouped within CC5. Higher levels of resistance to lincosamides, macrolides and fluoroquinolones were found in MRSA in comparison to MSSA. While 38% of SCCmec type IV isolates were resistant to 3 drug classes, with the remaining resistant to ≤2 classes, all SCCmec II isolates were resistant to at least 4 drug classes. Interestingly, SCCmec type II isolates were commonly isolated from keratitis and SCCmec types IV were more predominant in orbital abscess and cellulitis, suggesting differences in ocular tissue tropism among distinct MRSA clones. Conclusions: Distribution of MRSA lineages is consistent with a model where CC8 PVL-positive strains are better able to colonize and invade skin and soft tissues, resulting in infections such as orbital abscess, whereas CC5 type strains are better able to persist in the face of corneal defenses and infect at that site.
S = NIH grants EY024285, AI083214. CAPES, Brazil (P.J.M.B. Grant #9775-13-7).

2015 Agenda and Abstracts | < Previous | Next >