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).