Abstract

Purpose: Methicillin-resistant Staphylococcus aureus (MRSA) strains are commonly classified as hospital-acquired (HA) or community-acquired (CA). Typical HA-MRSA isolates are characterized by multidrug resistance and the SCCmec type II cassette, while CA-MRSA isolates are generally susceptible to more drug classes, are often of SCCmec type IV, and frequently carry the Panton-Valentine leukocidin (PVL) genes. This study determined the presence of traits characteristic for CA and HA strains in ocular MRSA isolates.Materials and Methods: Fifty-six recent ocular isolates, consisting of 40 MRSA and 16 methicillin-susceptible Staphylococcus aureus (MSSA) comparator strains, were characterized. Minimum inhibitory concentration (MIC) testing was done according to current Clinical and Laboratory Standards Institute guidelines. Detection of the PVL encoding genes and determination of the SCCmec type was done by polymerase chain reaction (PCR), while spa typing and cluster analysis was performed following DNA sequencing.Results: Of the 38 typeable MRSA isolates, 22 were of SCCmec type II and 16 were of SCCmec type IV. All SCCmec type II isolates were multidrug-resistant, lacked the PVL genes, and were of spa type t002 or closely related spa types. In contrast, the SCCmec type IV isolates were resistant to fewer classes of antimicrobial agents, often possessed the PVL genes (75.0%), and were of spa type t008 or closely related spa types.Conclusions: While the majority of ocular MRSA strains in this study fit the classical profile of HA- and CA-MRSA, some CA-MRSA isolates exhibited higher levels of antimicrobial resistance, which should be of particular concern to eye-care professionals. Furthermore, the apparent association of spa types and SCCmec types observed here warrants further investigation and suggests that spa typing may be useful in future HA- and CA-MRSA characterization studies.

Highlights

  • Staphylococcus aureus is a leading human pathogen of significant clinical importance, responsible for a wide array of infections from superficial skin infections to more serious invasive infections, including pneumonia, septicemia, and endocarditis

  • While the majority of ocular Methicillin-resistant Staphylococcus aureus (MRSA) strains in this study fit the classical profile of HAand community-acquired MRSA (CA-MRSA), some CA-MRSA isolates exhibited higher levels of antimicrobial resistance, which should be of particular concern to eye-care professionals

  • The apparent association of spa types and staphylococcal cassette chromosome mec” (SCCmec) types observed here warrants further investigation and suggests that spa typing may be useful in future HA- and CA-MRSA characterization studies

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Summary

Introduction

Staphylococcus aureus is a leading human pathogen of significant clinical importance, responsible for a wide array of infections from superficial skin infections to more serious invasive infections, including pneumonia, septicemia, and endocarditis. It is one of the most common ophthalmic pathogens ­recovered. MRSA pathogens were almost exclusively isolated from hospitals or hospital-associated facilities. Some hospitals have reported a predominance of CA-MRSA isolates over hospitalacquired MRSA (HA-MRSA) isolates.[9,10] the term “acquired” implies that the location of transmission is known, the HA- and CA-designations have been used to describe the phenotypic and molecular traits of MRSA isolates, as we have done in this study

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