Zyvox® Annual Appraisal of Potency and Spectrum (ZAAPS) program: report of linezolid activity over 9 years (2004-12).
OBJECTIVE
To summarize the activity and spectrum of linezolid and comparators tested against 7972 Gram-positive clinical isolates as part of the Zyvox(®) Annual Appraisal of Potency and Spectrum (ZAAPS) Program for 2012. Moreover, to provide molecular characterization for associated resistance mechanisms and epidemiological typing.


METHODS
A total of 7972 isolates were collected from 73 medical centres (33 countries) on five continents. Isolates were tested for susceptibility by broth microdilution following the CLSI M07-A9 document. MIC interpretations were based on CLSI and EUCAST criteria.


RESULTS
Linezolid showed MIC50 and MIC90 results of 1 and 2 mg/L, respectively, when tested against Staphylococcus aureus. These isolates were inhibited by linezolid at ≤2 mg/L, except for four S. aureus exhibiting higher MIC values (4-8 mg/L), which had cfr and/or target site mutations, including a first detection of cfr in an isolate from Brazil. Coagulase-negative staphylococci (CoNS) were susceptible to linezolid (MIC50/90, 0.5/1 mg/L), with only eight isolates exhibiting high MIC results (16-32 mg/L). These CoNS had cfr and/or single or multiple target site alterations in 23S rRNA and/or ribosomal proteins (L3, L4). The same species of linezolid-resistant CoNS collected from the same hospital were clonally related to those observed in previously surveyed years. Linezolid exhibited stable modal MIC and MIC50 results when tested against enterococci, regardless of the species or vancomycin resistance phenotype; in addition, linezolid inhibited all streptococci at ≤2 mg/L.


CONCLUSIONS
This surveillance report documents stable linezolid activity and susceptibility rates against a large and longitudinal collection of clinical isolates worldwide.
JMI Laboratories, North Liberty, IA 52317, USA rodrigo-mendes@jmilabs.com.
Rodrigo E
RE
Mendes
Pfizer Inc., Collegeville, PA 19426, USA.
Patricia A
PA
Hogan
JMI Laboratories, North Liberty, IA 52317, USA.
Jennifer M
JM
Streit
JMI Laboratories, North Liberty, IA 52317, USA Tufts University School of Medicine, Boston, MA 02111, USA.
Ronald N
RN
Jones
JMI Laboratories, North Liberty, IA 52317, USA.
Robert K
RK
Flamm
D000081:Acetamides / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D014943:Global Health; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006095:Gram-Positive Cocci / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D011159:Population Surveillance
D000081:Acetamides; D000890:Anti-Infective Agents; D023303:Oxazolidinones; D000069349:Linezolid
cfr; oxazolidinones; resistance; surveillance