Molecular Epidemiology of Methicillin-Resistant and Methicillin-SusceptibleStaphylococcus aureusIsolated from the Eye

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.

Molecular analysis and frequency of Staphylococcus aureus virulence genes isolated from bloodstream infections in a teaching hospital in Tianjin, China

“…These results differ from those of previous studies (Kim et al, 2011;Ho et al, 2012). The PVL genes, which encode a pore-forming cytotoxin and cause tissue necrosis and leukocyte destruction, are frequently present in community associated-MRSA (Vandenesch et al, 2003;Lo et al, 2008;Hesje et al, 2011). The prevalence of PVL genes in S. aureus from various samples is diverse, with 79.5% of S. aureus from recurrent furunculosis and 2.63% from lower respiratory tract infections harboring PVL genes Garbacz et al, 2011).…”

“…aureus is the causal pathogen of a wide range of infectious diseases ranging from skin and soft tissue infections to toxin-mediated diseases such as pneumonia and bacteremia (Holtfreter et al, 2007), many of which are caused by MRSA (Hesje et al, 2011). MRSA dissemination has become an important challenge at hospitals in all geographic areas owing to the emergence of isolates resistant to various antibiotic groups (Gomes et al, 2006).…”

Staphylococcus aureus Isolated from Endophthalmitis Are Hospital-Acquired Based on Panton-Valentine Leukocidin and Antibiotic Susceptibility Testing

“…Although the results of our study suggest that PVL is not a necessary virulence factor for SA endophthalmitis, this cytotoxin has been shown to confer greater virulence to SA infections elsewhere in the body. 6,8,9,18 Clinically, an important finding of this study is the determination that the majority of our SA isolates are resistant to second-and fourth-generation FQ anti-infectives as well as to methicillin. This is of great clinical importance, as these drugs are frequently given for prophylaxis before and after routine cataract extraction.…”

“…6 They characterized 38 isolates, and determined that 22 were HA strains which possessed the SCCmecII cassette for beta lactam resistance. All 22 HA isolates were PVL negative when tested with PCR.…”

“…4 Several studies over the past decade have shown that the PVL toxin genes are frequently expressed in communityacquired infection SA (CA-SA) strains and almost universally absent from hospital-acquired infection SA strains (HA-SA). [4][5][6] HA-SA tend to be resistant to multiple antibiotic classes, whereas CA-SA are more broadly susceptible to antibiotics. 4,[7][8][9][10] To date, there has been no specific study that evaluates the origin of SA implicated in endophthalmitis for the PVL gene products.…”