title: An international activity and spectrum analysis of linezolid: ZAAPS Program results for 2011.
abstract: Through a continuing resistance surveillance monitoring program, linezolid was shown to maintain its spectrum and potency against a collection of 8059 clinically relevant Gram-positive strains collected from patients at 79 medical centers in 33 countries and Hong Kong. Linezolid MIC90 values were 2 μg/mL for methicillin-resistant and -susceptible Staphylococcus aureus and enterococci, and the MIC90 value was 1 μg/mL for coagulase-negative staphylococci (CoNS), β-hemolytic streptococci, Streptococcus pneumoniae, and viridans group streptococci. Reference broth microdilution susceptibility testing for linezolid demonstrated a 99.83% susceptibility rate for all organisms. All S. aureus were inhibited by ≤2 μg/mL. Three (0.3%) of 928 strains of CoNS had a linezolid MIC of 4 μg/mL and contained the cfr resistance gene; 1 also had a mutation in L3. There were 14 linezolid-resistant strains detected from 7 countries (Brazil [5], France [1], Germany [2] Greece [2], Italy [2], Ireland [1], and Spain [1]) representing 5 species (E. faecium, S. capitis, S. epidermidis, S. hominis, S. lugdenensis). A mobile cfr gene was noted in 2 species having elevated linezolid MIC values; one was a S. haemolyticus isolate with a MIC at 4 μg/mL. Resistance rates were as follows for the 6 groups of organisms sampled in the 2011 ZAAPS Program: CoNS, 1.2%; enterococci, 0.39%; among S aureus, S. pneumoniae, viridans group streptococci, and β-hemolytic streptococci, no resistance was detected. As the activities of commonly used antimicrobials continue to be compromised by evolving resistance mechanisms in Gram-positive pathogens, linezolid-resistant strains remain uncommon and without increasing occurrence.
authors.affiliation: JMI Laboratories, North Liberty, IA 52317, USA. robert-flamm@jmilabs.com
authors.forename: Robert K
authors.initials: RK
authors.lastname: Flamm
authors.forename: Rodrigo E
authors.initials: RE
authors.lastname: Mendes
authors.forename: James E
authors.initials: JE
authors.lastname: Ross
authors.forename: Helio S
authors.initials: HS
authors.lastname: Sader
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001938:Brazil; D002648:Child; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D016983:Enterococcus / Q000187:drug effects / Q000302:isolation & purification; D005260:Female; D005602:France; D005858:Germany; D006115:Greece; D006723:Hong Kong; D006801:Humans; D007223:Infant; D007494:Ireland; D007558:Italy; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D012329:RNA, Bacterial / Q000302:isolation & purification; D015203:Reproducibility of Results; D013030:Spain; D013057:Spectrum Analysis / Q000379:methods*; D013210:Staphylococcus / Q000187:drug effects / Q000302:isolation & purification; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification; D013291:Streptococcus / Q000187:drug effects / Q000302:isolation & purification; D016896:Treatment Outcome; D034363:Viridans Streptococci / Q000187:drug effects / Q000302:isolation & purification
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D012329:RNA, Bacterial; D000069349:Linezolid