Emergence of multidrug-resistant Salmonella enterica serotype Newport infections resistant to expanded-spectrum cephalosporins in the United States

J Infect Dis. 2003 Dec 1;188(11):1707-16. doi: 10.1086/379668. Epub 2003 Nov 18.


We describe a field investigation in New England that identified the emergence and epidemiology of new strains of multidrug-resistant Salmonella, Newport-MDRAmpC, and summarize the Center for Disease Control and Prevention's surveillance data for these infections. In Massachusetts, the prevalence of Newport-MDRAmpC among Salmonella serotype Newport isolates obtained from humans increased from 0% (0/14) in 1998 to 53% (32/60) in 2001 (P<.001). In a retrospective case-control study, infection with Newport-MDRAmpC was domestically acquired and was associated with exposure to a dairy farm. Isolates from both humans and cattle had indistinguishable or closely related antibiograms and pulsed-field gel electrophoresis patterns. Nationally, the prevalence of ceftriaxone-resistant Salmonella increased from 0.5% in 1998 to 2.4% in 2001; 85% of the isolates in 2001 were Newport-MDRAmpC, and at least 27 states have isolated these strains from humans, cattle, or ground beef. These data document the widespread emergence of Newport-MDRAmpC strains in the United States and show that the 5-fold increase in the prevalence of Salmonella resistant to expanded-spectrum cephalosporins, between 1998 and 2001, is primarily due to the emergence of Newport-MDRAmpC strains.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Bacterial Proteins*
  • Case-Control Studies
  • Cattle
  • Cephalosporin Resistance*
  • Child
  • Child, Preschool
  • Drug Resistance, Multiple, Bacterial
  • Female
  • Food Microbiology
  • Humans
  • Infant
  • Male
  • Middle Aged
  • Salmonella Infections / etiology
  • Salmonella enterica / drug effects*
  • Salmonella enterica / genetics
  • Serotyping
  • beta-Lactamases / genetics*


  • Bacterial Proteins
  • AmpC beta-lactamases
  • beta-Lactamases