title: Antimicrobial susceptibility trends among gram-positive and -negative clinical isolates collected between 2005 and 2012 in Mexico: results from the Tigecycline Evaluation and Surveillance Trial.
abstract: BACKGROUND
  The Tigecycline Evaluation and Surveillance Trial (T.E.S.T) is a global antimicrobial surveillance study of both gram-positive and gram-negative organisms. This report presents data on antimicrobial susceptibility among organisms collected in Mexico between 2005 and 2012 as part of T.E.S.T., and compares rates between 2005-2007 and 2008-2012.
  
  
  METHODS
  Each center in Mexico submitted at least 200 isolates per collection year; including 65 gram-positive isolates and 135 gram-negative isolates. Minimum inhibitory concentrations (MICs) were determined using Clinical Laboratory Standards Institute (CLSI) broth microdilution methodology and antimicrobial susceptibility was established using the 2013 CLSI-approved breakpoints. For tigecycline US Food and Drug Administration (FDA) breakpoints were applied. Isolates of E. coli and K. pneumoniae with a MIC for ceftriaxone of >1 mg/L were screened for ESBL production using the phenotypic confirmatory disk test according to CLSI guidelines.
  
  
  RESULTS
  The rates of some key resistant phenotypes changed during this study: vancomycin resistance among Enterococcus faecium decreased from 28.6 % in 2005-2007 to 19.1 % in 2008-2012, while β-lactamase production among Haemophilus influenzae decreased from 37.6 to 18.9 %. Conversely, methicillin-resistant Staphylococcus aureus increased from 38.1 to 47.9 %, meropenem-resistant Acinetobacter spp. increased from 17.7 to 33.0 % and multidrug-resistant Acinetobacter spp. increased from 25.6 to 49.7 %. The prevalence of other resistant pathogens was stable over the study period, including extended-spectrum β-lactamase-positive Escherichia coli (39.0 %) and Klebsiella pneumoniae (25.0 %). The activity of tigecycline was maintained across the study years with MIC90s of ≤2 mg/L against Enterococcus spp., S. aureus, Streptococcus agalactiae, Streptococcus pneumoniae, Enterobacter spp., E. coli, K. pneumoniae, Klebsiella oxytoca, Serratia marcescens, H. influenzae, and Acinetobacter spp. All gram-positive organisms were susceptible to tigecycline and susceptibility among gram-negatives ranged from 95.0 % for K. pneumoniae to 99.7 % for E. coli.
  
  
  CONCLUSIONS
  Antimicrobial resistance continues to be high in Mexico. Tigecycline was active against gram-positive and gram-negative organisms, including resistant phenotypes, collected during the study.
authors.affiliation: Hospital Civil de Guadalajara, Fray Antonio Alcalde, Instituto de Patologia Infecciosa y Experimental, Centro Universitario Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico. rayomorfin@gmail.com.
authors.forename: Rayo
authors.initials: R
authors.lastname: Morfin-Otero
authors.affiliation: Hospital Civil de Guadalajara, Fray Antonio Alcalde, Instituto de Patologia Infecciosa y Experimental, Centro Universitario Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico. idfcolima@yahoo.com.
authors.forename: Eduardo Rodriguez
authors.initials: ER
authors.lastname: Noriega
authors.affiliation: Pfizer Inc, Collegeville, PA, USA. michael.dowzicky@pfizer.com.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dowzicky
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002648:Child; D024881:Drug Resistance, Bacterial; D062665:Epidemiological Monitoring; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology / Q000382:microbiology*; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D015994:Incidence; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents