1171. Linezolid-Resistant Staphylococcus aureus (LRSA) in Children
Session: Poster Abstract Session: Staphylococcus aureus Infections in Children
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Linezolid is an oxazolidinone antibiotic approved for methicillin-resistant Staphylococcus aureus (MRSA) infection and is considered one of the last options for treatment of MRSA.  Emergence of LRSA is concerning because it limits treatment options available for multi-drug resistant S. aureus.  Our institution has identified 5 patients since 2008 with LRSA; all of whom have cystic fibrosis (CF). The purpose of this study was to describe demographics and characteristics of patients with documented LRSA.

Methods: The study was a retrospective, descriptive review of patients with identified LRSA at a free-standing, 317-bed pediatric institution.  Data abstracted included patient demographics, rate of methicillin-susceptible S. aureus (MSSA), MRSA and additional organisms, and history of anti-infective medications.  Cumulative linezolid exposure, time to LRSA acquisition, LRSA susceptibility patterns, LRSA treatment regimens, and outcomes were recorded.

Results: Between September 2008 and November 2010, 5 patients were identified with LRSA (2 males, age range 8-14 years).  All patients had a history of MRSA (3 of 5 had a history of MSSA). Other organisms identified included Pseudomonas, Aspergillus, Burkholderia, and Stenotrophomonas.  The most common concomitant anti-infective agents were oral azithromycin, ciprofloxacin, and various inhaled antibiotics (tobramycin, colistin, vancomycin).  Four of 5 patients had exposure to linezolid prior to LRSA identification.  Cumulative linezolid exposure ranged from 114-453 days; the longest was treated for Mycobacterium abscessus infection.  LRSA was treated with a variety of antistaphylococcal agents; two patients received linezolid despite in vitro resistance.  No patients died.

Conclusion: Providers should be aware of LRSA as an emerging pathogen in cystic fibrosis patients.  Prolonged linezolid duration may be associated with development of LRSA; however, acquisition of LRSA appears to be possible without antecedent drug exposure.  Continued research into the mechanisms of linezolid resistance is needed.

Subject Category: A. Antimicrobial agents and Resistance

Diana Yu, PharmD, BCPS1, Leslie Stach, PharmD, BCPS1, Jason Newland, MD2, Philip Black, MD1 and Mary Anne Jackson, MD, FIDSA1, (1)Children's Mercy Hospitals and Clinics, Kansas City, MO, (2)Children's Mercy Hospital and Clinics, Kansas City, MO


D. Yu, None

L. Stach, None

J. Newland, None

P. Black, None

M. A. Jackson, None

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