title: Increase in resistance to ceftriaxone and nonsusceptibility to ciprofloxacin and decrease in multidrug resistance among Salmonella strains, United States, 1996-2009.
abstract: BACKGROUND
  Salmonella is a major bacterial pathogen transmitted commonly through food. Increasing resistance to antimicrobial agents (e.g., ceftriaxone, ciprofloxacin) used to treat serious Salmonella infections threatens the utility of these agents. Infection with antimicrobial-resistant Salmonella has been associated with increased risk of severe infection, hospitalization, and death. We describe changes in antimicrobial resistance among nontyphoidal Salmonella in the United States from 1996 through 2009.
  
  
  METHODS
  The Centers for Disease Control and Prevention's National Antimicrobial Resistance Monitoring System conducts surveillance of resistance among Salmonella isolated from humans. From 1996 through 2009, public health laboratories submitted isolates for antimicrobial susceptibility testing. We used interpretive criteria from the Clinical and Laboratory Standards Institute and defined isolates with ciprofloxacin resistance or intermediate susceptibility as nonsusceptible to ciprofloxacin. Using logistic regression, we modeled annual data to assess changes in antimicrobial resistance.
  
  
  RESULTS
  From 1996 through 2009, the percentage of nontyphoidal Salmonella isolates resistant to ceftriaxone increased from 0.2% to 3.4% (odds ratio [OR]=20, 95% confidence interval [CI] 6.3-64), and the percentage with nonsusceptibility to ciprofloxacin increased from 0.4% to 2.4% (OR=8.3, 95% CI 3.3-21). The percentage of isolates that were multidrug resistant (resistant to ≥3 antimicrobial classes) decreased from 17% to 9.6% (OR=0.6, 95% CI 0.5-0.7), which was driven mainly by a decline among serotype Typhimurium. However, multidrug resistance increased from 5.9% in 1996 to a peak of 31% in 2001 among serotype Newport and increased from 12% in 1996 to 26% in 2009 (OR=2.6, 95% CI 1.1-6.2) among serotype Heidelberg.
  
  
  CONCLUSIONS
  We describe an increase in resistance to ceftriaxone and nonsusceptibility to ciprofloxacin and an overall decline in multidrug resistance. Trends varied by serotype. Because of evidence that antimicrobial resistance among Salmonella is predominantly a consequence of antimicrobial use in food animals, efforts are needed to reduce unnecessary use, especially of critically important agents.
authors: Centers for Disease Control and Prevention, Atlanta, Georgia 30329, USA. fhm1@cdc.gov
authors: Felicita
authors: F
authors: Medalla
authors: Robert M
authors: RM
authors: Hoekstra
authors: Jean M
authors: JM
authors: Whichard
authors: Ezra J
authors: EJ
authors: Barzilay
authors: Tom M
authors: TM
authors: Chiller
authors: Kevin
authors: K
authors: Joyce
authors: Regan
authors: R
authors: Rickert
authors: Amy
authors: A
authors: Krueger
authors: Andrew
authors: A
authors: Stuart
authors: Patricia M
authors: PM
authors: Griffin
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002443:Ceftriaxone / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D002939:Ciprofloxacin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012475:Salmonella / Q000187:drug effects* / Q000302:isolation & purification; D012480:Salmonella Infections / Q000453:epidemiology / Q000382:microbiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D002443:Ceftriaxone