May 2012

Document Type


Degree Name



Dept. of Public Health and Preventive Medicine


Oregon Health & Science University


Background: Non-typhoidal Salmonella (NTS) infects an estimated 1.4 million persons in the US every year. Studies have demonstrated the health consequences of infection with antimicrobial resistant NTS, but few population level epidemiologic investigations have examined exposures and trends in resistance. Therefore, our objective was to explore NTS resistance in Oregon. Methods: The Oregon Health Authority, Public Health Division performs surveillance on 3.6 million persons and ascertains patient exposure history, demographics, and outcomes for all culture-confirmed cases of Salmonellosis. Positive isolates are serotyped and antimicrobial susceptibility testing is performed. We defined resistance as clinically important (CIR) if an isolate exhibited decreased susceptibility to ampicillin, ceftriaxone, ciprofloxacin, gentamicin, or trimethoprim-sulfamethoxazole. We analyzed trends in antimicrobial resistance and modeled risk factors for acquiring a resistant isolate compared to cases with pan-susceptible isolates. Results: During 2004-2009, 80.4% (n=1813) of all Oregon confirmed Salmonellosis cases had exposure information and susceptibility testing. Among these patients, 16.8% (n=305) had isolates resistant to >=1 CIR antibiotic and 55.3% (n=1,002) were susceptible to all antibiotics screened. The following serotypes had increased resistance compared to serotype Enteriditis: Typhimurium (adjusted odds ratio [aOR] 4.51, <0.01), Heidelberg (aOR 5.01, p<0.01), Typhimurium var Copenhagen (aOR 13.86, p<0.01), and Newport (aOR 7.11, p<0.01). Relative to pan-susceptible isolates, the percentage of isolates that were CIR significantly increased (15.7% in 2004 to 26.7% in 2009, p<0.01). Year (aOR 1.15 per year, p<0.01), travel to East or Southeast Asia (aOR 6.86, p<0.01), and outbreak clusters (aOR 0.55, p<0.01) were significantly associated with resistance to >=1 clinically important antibiotic. Conclusion: Antimibiotic resistance among NTS increased in Oregon between 2004 and 2009. Clinically important resistance was positively associated with international travel to East and Southeast Asia and negatively associated with outbreak cases.




School of Medicine



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