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Comparative activity of oritavancin against recent genetically diverse methicillin-resistant Staphylococcus aureus isolates

Abstract number: P1856

Arhin F.F., Kurepina N., Kreiswirth B., Sarmiento I., Parr Jr. T.R., Moeck G.

Objectives: Oritavancin (ORI) is a lipoglycopeptide with bactericidal activity against Gram-positive bacteria including drug-resistant S. aureus. This study describes ORI activity against recent genetically diverse MRSA isolates compared to vancomycin (VAN), teicoplanin (TEI), oxacillin (OXA), erythromycin (ERY), daptomycin (DAP), ciprofloxacin (CIP) and linezolid (LIN).

Methods: Strains (n = 58) were clinical isolates obtained between 2005 and 2006 from hospitals in the New York/New Jersey, USA area. Broth microdilution MICs were determined according to CLSI guidelines. Identification of the Panton-Valentine leukocidin (pvl) genes was by polymerase chain reaction (PCR). Multiplex PCR was used for staphylococcal cassette chromosome (SCC) mec typing. Staphylococcal protein A (spa) typing was by PCR followed by sequencing of the PCR products.

Results: The MRSA isolates were genetically diverse and included classical community-associated USA300 isolates (n = 17), PVL+ strains (n = 33) and PVL- strains (n = 25). Majority (95%) of the PVL+ isolates were typed as SCCmec IV. Of the PVL- isolates, 60% were SCCmec II and 40% were SCCmec IV.ORI MIC90 s were identical for the isolates regardless of the PVL type, SCCmec type or spa type. Based on MIC90 s, ORI was more potent than the comparators used in this study. ORI MIC90 s against all MRSA were 16-, 8-, and 4-fold lower than those for the LIN, DAP, and VAN, respectively.

Conclusions: ORI MICs did not exceed 0.25 mg/L for any MRSA strain in this study. ORI activity was unaffected by presence of PVL, SCCmec type or spa type. Finally, MRSA isolates were more susceptible to ORI than to the comparators used in this study.

AgentMIC range (MIC90), mg/L
 Total (n = 58)PVL+ (n = 33)PVL- (n = 25)SCCmecII (n = 16)SCCmecIV (n = 42)
ORI0.03–0.250.03–0.250.06–0.250.06–0.250.03–0.25
 (0.25)(0.25)(0.25)(0.25)(0.25)
OXA4–>644–648–>6432–>644–>64
 (64)(32)(>64)(>64)(32)
VAN0.25–20.25–10.25–20.25–20.25–2
 (1)(1)(2)(2)(1)
TEI0.25–20.25–10.25–20.25–10.25–2
 (1)(1)(2)(1)(1)
DAP0.5–40.5–40.5–40.5–40.5–4
 (2)(1)(2)(2)(1)
CIP0.12–>640.12–>640.25–>6432–>640.12–>64
 (>64)(>64)(>64)(>64)(>64)
ERY0.25–>640.25–>640.5–>642–>640.25–>64
 (>64)(>64)(>64)(>64)(>64)
LIN1–641–641–81–81–64
 (4)(4)(4)(4)(4)

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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