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Linezolid resistance since 2001: SENTRY Antimicrobial Surveillance Program
Alan H Mutnick1, Victoria Enne, Ronald N Jones
1Pharmacology, The JONES Group/JMI Laboratories, North Liberty, IA 52317-9258, USA. alan-mutnick@jmilabs.com
The Annals of Pharmacotherapy
|May 30, 2003
Summary
Linezolid resistance in gram-positive cocci remains rare, with only 8 resistant strains identified. Emerging resistance is not limited to enterococci, necessitating wider testing and surveillance for oxazolidinone therapy.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Oxazolidinones, including linezolid, are effective against gram-positive cocci.
- Linezolid is a primary treatment for vancomycin-resistant strains.
- Rare cases of linezolid resistance have been reported with prolonged use.
Purpose of the Study:
- To identify and characterize the first linezolid-resistant organisms detected by the SENTRY Antimicrobial Surveillance Program.
- To screen over 40,000 gram-positive cocci isolates for linezolid resistance between 1998 and 2000.
Main Methods:
- Identified 8 linezolid-resistant strains from 8 patients in the US between 2001-2002.
- Tested bloodstream, respiratory, skin/soft tissue, and urinary tract isolates including Enterococcus faecalis, Enterococcus faecium, Staphylococcus epidermidis, and Streptococcus oralis.
- Confirmed resistance using broth microdilution, Etest, and disk diffusion methods.
Main Results:
- All 8 strains exhibited elevated Minimum Inhibitory Concentrations (MICs) for linezolid and AZD2563.
- Two strains were also vancomycin-resistant; all enterococci and S. oralis were erythromycin-resistant.
- E. faecium strains were penicillin-resistant but susceptible to quinupristin/dalfopristin; only 3 patients had prior linezolid exposure.
Conclusions:
- Linezolid resistance is rare (0.08% of monitored isolates), but resistance is emerging in non-enterococcal species.
- Clinical laboratories should increase linezolid susceptibility testing, particularly for patients on oxazolidinone therapy.
- Longitudinal surveillance is crucial to track resistance trends, understand mechanisms, and guide treatment strategies.