EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS
Location: Bacterial Epidemiology and Antimicrobial Resistance
Title: Salmonella Newport as Reported by the Animal Arm of the National Antimicrobial Resistance Monitoring System Enteric Bacteria (NARMS)
Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: March 21, 2007
Publication Date: July 8, 2007
Citation: Cray, P.J., Bailey, J.S., Jackson, C.R., Frye, J.G., Haro, J.H., Mcglinchey, B., Plumblee, J. 2007. Salmonella Newport as Reported by the Animal Arm of the National Antimicrobial Resistance Monitoring System Enteric Bacteria (NARMS). International Association for Food Protection. T8-01:112.
Introduction: Since the early 1990’s there has been increasing awareness and concern regarding the development of antimicrobial resistance among bacteria of public health significance. Reports targeting zoonotic bacteria, and in particular Salmonella species, suggest that resistance is trending upward. Of particular concern starting in 2000, was the emergence of multiple drug resistant (MDR) Salmonella Newport.
Purpose: The purpose of this study was to determine the trend of S. Newport submitted to the animal arm of NARMS for genotypic and phenotypic characterization from 1997 through 2005.
Methods: Isolates submitted to NARMS were tested for susceptibility to 16 antimicrobials using a custom made panel and a semi-automated broth microdilution system (Sensititre, Trek Diagnostics, Cleveland, OH). Isolates were further characterized by pulsed field gel electrophoresis (PFGE)
Results: Of the 48,238 Salmonella isolates tested from 1997 through 2005, the percent identified as S. Newport increased from 0.75% (n=18) in 1997 to a high of 9.0% (n=483) in 2003, declining to 3.2% (n=119) in 2005. The majority (n=1660; 3.4%) originated from diagnostic submissions followed by slaughter (n=645; 1.3%) and on-farm (n=100; 0.2%) sources. Slaughter isolates originated most often from cattle. The percent of isolates resistant to 2 or more antimicrobials averaged 73.5% from 2000 through 2005. PFGE analysis indicated a high degree of heterogeneity among the isolates. Interestingly, isolates which were indistinguishable by PFGE were not necessarily indistinguishable by phenotypic analysis.
Significance: These data indicate that the percent of S. Newport originating from animals and submitted to the animal arm of NARMS appears to be declining. However, the MDR phenotype is persisting among a high percentage of the isolates. Continued monitoring and further characterization of isolates is warranted.