Table 3.
Antimicrobial resistance of Salmonella outbreak isolates from human and pig ear treat samples.
| Antimicrobial | Human N = 137 n (%) | Pig ear treats N = 135 n (%) | Dog N = 4 n (%) | Totala n (%) |
|---|---|---|---|---|
| Amikacin | NT | NT | 1 (25%) | 1/4 (25%) |
| Ampicillin | 105 (77%) | 50 (37%) | 4 (100%) | 159/276 (58%) |
| Amoxicillin-clavulanic acid | NT | NT | 4 (100%) | 4/4 (100%) |
| Azithromycin | 1 (1%) | 0 (0%) | NT | 1/272 (<1%) |
| Cefazolin | NT | NT | 2 (50%) | 2/4 (50%) |
| Cefpodoxime | NT | NT | 1 (25%) | 1/4 (25%) |
| Ceftriaxone | 0 (0%) | 0 (0%) | NT | 0/272 (0%) |
| Cephalexin | NT | NT | 2 (50%) | 2/4 (50%) |
| Chloramphenicol | 46 (34%) | 54 (40%) | 1 (25%) | 101/276 (37%) |
| Ciprofloxacinb | 84 (61%) | 45 (33%) | NT | 129/272 (47%) |
| Doxycycline | NT | NT | 1 (25%) | 1/4 (25%) |
| Fosfomycinc,d | 1 (1%) | 4 (3%) | NT | 5/272 (2%) |
| Gentamicin | 67 (49%) | 8 (6%) | 2 (50%) | 77/276 (28%) |
| Kanamycinc,d | 4 (3%) | 2 (2%) | NT | 6/272 (2%) |
| Meropenem | 0 (0%) | 0 (0%) | NT | 0/272 (0%) |
| Nalidixic acidc | 63 (53%) | 5 (5%) | NT | 68/272 (32%) |
| Streptomycinc | 65 (48%) | 17 (13%) | NT | 82/272 (30%) |
| Sulfisoxazole | 61 (45%) | 15 (11%) | NT | 76/272 (28%) |
| Tetracycline | 105 (77%) | 59 (44%) | 1 (25%) | 165/276 (60%) |
| Trimethoprimd | 39 (28%) | 52 (39%) | NT | 91/272 (33%) |
| Trimethoprim-sulfamethoxazole | 3 (2%) | 12 (9%) | 1 (25%) | 16/272 (6%) |
| Any resistance | 126 (92%) | 87 (64%) | 4 (100%) | 217/276 (79%) |
| Multidrug resistancee | 105 (77%) | 58 (43%) | 2 (50%) | 165/276 (60%) |
| Clinically important resistancef | 125 (90%) | 82 (61%) | 4 (100%) | 211/276 (76%) |
Antimicrobial resistance information was available for isolates from 137 ill people, including two assessed by standard antimicrobial susceptibility testing (AST) only, 24 with resistance predicted by whole genome sequencing (WGS) and confirmed by AST, and 111 with resistance predicted by WGS only. Pig ear treat isolates were only evaluated by WGS. Dog isolates were only evaluated by AST. Two pig ear treat isolates and 17 human isolates were not available for resistance screening.
Total in each row based on the number tested for that given antimicrobial. NT = Not tested.
Percentages reflect ciprofloxacin nonsusceptibilty (intermediate interpretation by AST or single quinolone resistance mechanism). No isolates showed resistance by AST or harbored multiple quinolone resistance mechanisms.
Antimicrobial resistance information was available for a subset of isolates: fosfomycin (n = 270), kanamycin (n = 270), nalidixic acid (n = 214), streptomycin (n = 270).
Resistance information was predicted based on WGS alone for these antimicrobials.
Multidrug resistance was defined as resistance (or nonsusceptibility, for ciprofloxacin) to ≥3 antimicrobial classes.
Clinically important resistance was defined as resistance (or nonsusceptibility, for ciprofloxacin) to ≥1 antimicrobial recommended for treatment of salmonellosis (i.e., ampicillin, azithromycin, ceftriaxone, ciprofloxacin, or trimethoprim-sulfamethoxazole).