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Volume 27, Number 6—June 2021

Increased Incidence of Antimicrobial-Resistant Nontyphoidal Salmonella Infections, United States, 2004–2016

Felicita MedallaComments to Author , Weidong Gu, Cindy R. Friedman, Michael Judd, Jason Folster, Patricia M. Griffin, and Robert M. Hoekstra
Author affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Main Article

Table 1

Number and percentage of antimicrobial-resistant nontyphoidal Salmonella isolates, by serotype and resistance category, United States, 2004–2016*

Resistance category No. (%) isolates
Enteritidis, n = 5,206 Typhimurium, n = 4,404 Newport, n = 3,140 I 4,[5],12:i:-, n = 1,158 Heidelberg, n = 974 Other fully serotyped, n = 12,878 Not fully serotyped, n = 505 Total nontyphoidal Salmonella, N = 28,265
Any clinically important resistance† 548 (10.5) 1,197 (27.2) 284 (9.0) 389 (33.6) 240 (24.6) 843 (6.5) 45 (8.9) 3,546 (12.5)
Multidrug resistance‡ 114 (2.2) 1,178 (26.7) 271 (8.6) 382 (33.0) 204 (20.9) 727 (5.6) 36 (7.1) 2,912 (10.3)
Amp-only§ 152 (2.9) 897 (20.4) 30 (1.0) 319 (27.5) 120 (12.3) 311 (2.4) 28 (5.5) 1,857 (6.6)
Cef/Amp§¶ 15 (0.3) 212 (4.8) 237 (7.5) 39 (3.4) 116 (11.9) 212 (1.6) 4 (0.8) 835 (3.0)
Cipro§# 381 (7.3) 88 (2.0) 17 (0.5) 31 (2.7) 4 (0.4) 320 (2.5) 13 (2.6) 854 (3.0)

*Amp-only, resistant to ampicillin (MIC >32 µg/mL) but susceptible to ceftriaxone and ciprofloxacin; Cef/Amp, resistant to ceftriaxone (MIC >4 µg/mL) and ampicillin; Cipro, nonsusceptible to ciprofloxacin (MIC >0.12 µg/mL) but susceptible to ceftriaxone; NTS, nontyphoidal Salmonella, which includes isolates serotyped as Enteritidis, Typhimurium, Newport, I 4,[5],12:i:-, and Heidelberg, isolates serotyped as other than those 5, and those not fully serotyped.
†Includes any of the 3 clinically important resistance patterns (i.e., resistant to ceftriaxone, resistant to ampicillin, or nonsusceptible to ciprofloxacin). Isolates might have resistance to other agents tested.
‡Resistant to >3 classes of antimicrobial agents.
§Amp-only, Cef/Amp, and Cipro are mutually exclusive categories of clinically important resistance.
¶Of the 835 isolates with Cef/Amp resistance, 78 (0.3% of all nontyphoidal Salmonella isolates) were nonsusceptible to ciprofloxacin. Of the 78 isolates, 71 (91%) had ciprofloxacin MICs within the intermediate range (i.e., 0.12–0.5) (Appendix Figure 6). These 78 isolates were not included in the Cipro category.
#Of the 854 isolates, 785 (92%) had ciprofloxacin MICs within the intermediate range (Appendix Figure 6).

Main Article

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