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In vitro activity of linezolid as assessed through the 2013 LEADER surveillance program
Robert K Flamm1, Rodrigo E Mendes1, Patricia A Hogan2
1JMI Laboratories, North Liberty, IA 52317, USA.
Diagnostic Microbiology and Infectious Disease
|January 31, 2015
Summary
The 2013 LEADER surveillance program found linezolid remains highly effective against Gram-positive bacteria, with 99.83% susceptibility. Few resistant isolates were identified, indicating stable antimicrobial activity.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Linezolid is a critical antibiotic for treating serious Gram-positive bacterial infections.
- Monitoring antimicrobial activity is essential to detect emerging resistance patterns.
Purpose of the Study:
- To evaluate the in vitro activity of linezolid against key Gram-positive pathogens in the United States during 2013.
- To assess the prevalence of linezolid resistance and identify potential resistance mechanisms.
Main Methods:
- The LEADER surveillance program collected 7183 Gram-positive bacterial isolates from 60 US medical centers.
- Minimum Inhibitory Concentration 90 (MIC90) values and susceptibility testing were performed for linezolid and comparator agents.
- Resistance mechanisms, including the cfr gene, were investigated in non-susceptible isolates.
Main Results:
- Linezolid demonstrated potent in vitro activity, with MIC90 values of 1 μg/mL across six major Gram-positive pathogen groups.
- Overall susceptibility to linezolid was high at 99.83%, with only 12 non-susceptible isolates.
- The cfr resistance mechanism was identified in three isolates (two Staphylococcus aureus and one Enterococcus faecium).
Conclusions:
- Linezolid maintains stable and effective in vitro activity against a broad spectrum of Gram-positive bacteria.
- Emerging resistance, though rare, warrants continued surveillance, particularly concerning clonal dissemination.
- The findings support the continued utility of linezolid in clinical practice for Gram-positive infections.
