1393. Antimicrobial Resistance among Nontyphoidal Salmonella Isolated from Blood in the United States, 2003–2013
Session: Oral Abstract Session: Resistance Mechanisms
Saturday, October 10, 2015: 11:15 AM
Room: 25--ABC
Background: CDC estimates that nontyphoidal Salmonella (NTS) causes 1.2 million US illnesses each year and an estimated 100,000 isolates are antimicrobial-resistant. Most NTS infections cause gastroenteritis, but antimicrobial-resistant NTS may result in bacteremia, treatment failure, and poor clinical outcomes. We describe antimicrobial resistance (AR) among NTS blood isolates using data from the National Antimicrobial Resistant Monitoring System (NARMS).

Methods: During 2003–2013, health departments from all 50 states forwarded every 20th NTS isolate to the NARMS program at CDC for antimicrobial susceptibility testing. Based on CLSI interpretive standards, isolates were classified as fully susceptible, non-susceptible (NS) to ≥1 antimicrobial agent, and having clinically important resistance (CIR) if NS to ≥1 of either ampicillin, ceftriaxone, ciprofloxacin, or TMP-SMX. Odds ratios (OR) and 95% confidence intervals (CI) were used to compare resistance patterns, serotypes, and patient characteristics for NTS isolated from blood vs. stool. 

Results: Of 20,866 NTS blood and stool isolates, 1,189 (6%) were from blood. Bacteremia was significantly associated with male sex, age ≥65 years, and certain serotypes, including Dublin, Sandiego, Schwarzengrund, Panama, Heidelberg, and Enteritidis. Blood isolates were more likely than stool isolates to be NS to ≥1 agent (OR, 1.7; 95% CI, 1.5–1.9); this association was significant for serotypes Typhimurium, Enteritidis, Javiana, and Panama. Blood isolates were most commonly NS to tetracycline (19%), ampicillin (17%), streptomycin (16%), and sulfonamides (16%). CIR was also more common among blood isolates (OR, 1.8; 95% CI, 1.6–2.1), including non-susceptibility to ampicillin (OR, 1.9; 95% CI, 1.6–2.2), ceftriaxone (OR, 1.6; 95% CI, 1.2–2.2), ciprofloxacin (OR, 2.1; 95% CI, 1.6–2.8), and TMP-SMX (OR, 2.2; 95% CI, 1.5-3.1).

Conclusion: NTS blood isolates were more likely to be NS to ≥1 agent and clinically important treatment agents. AR to first-line antibiotics in patients with NTS bacteremia is a serious public health concern and is important for informing  clinical decisions. Judicious use of antimicrobials in both humans and food-producing animals is crucial to limit resistance.

Kristina Angelo, DO, Jared Reynolds, MPH, Beth Karp, DVM, MPH, DACVPM, Jason Folster, PhD and Cindy Friedman, MD, Centers for Disease Control and Prevention, Atlanta, GA


K. Angelo, None

J. Reynolds, None

B. Karp, None

J. Folster, None

C. Friedman, None

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