TABLE 1.
Frequency of resistance to antimicrobial agents in Salmonella serovar Virchow isolates from human and poultry sources
| Resistance to:a | Human isolates (n = 243)
|
Chicken isolates (n = 93)
|
P valueb | ||
|---|---|---|---|---|---|
| No. | % | No. | % | ||
| No antibiotic agents | 13 | 5.3 | 2 | 2.2 | NS |
| Colistin | 4 | 1.6 | 15 | 16.1 | <0.001 |
| Polymyxin B | 0 | 0 | 14 | 15.1 | <0.001 |
| Ampicillin | 31 | 12.8 | 19 | 20.7 | NS |
| Neomycin | 1 | 0.4 | 4 | 4.3 | NS |
| Gentamicin | 1 | 0.4 | 0 | 0.0 | NS |
| Nalidixic acid | 221 | 90.9 | 86 | 92.5 | NS |
| Trimethoprim-sulfamethoxazole | 113 | 46.5 | 52 | 55.9 | NS |
| Tetracycline | 124 | 51.0 | 59 | 63.4 | 0.05 |
| Chloramphenicol | 85 | 35.0 | 37 | 39.8 | NS |
| Streptomycin | 125 | 51.4 | 48 | 51.6 | NS |
| Ciprofloxacin | 0 | 0 | 0 | 0 | NS |
| Ceftriaxone | 0 | 0 | 0 | 0 | NS |
| ≥4 Antibiotic agents | 113 | 46.5 | 52 | 55.9 | NS |
a
Antibiotics and the amounts in disks were as follows: chloramphenicol, nalidixic acid, neomycin, ceftriaxone, tetracycline, and polymyxin B, 30 μg each; ampicillin, streptomycin, and colistin, 10 μg each; ciprofloxacin and gentamicin, 5 μg each; trimethoprim-sulfamethoxazole 1:19, 25 μg. The quality control strains that were used for the susceptibility testing are Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853.
b
NS, not significant. For all NS cell entries, the difference between human isolates and chicken isolates is not statistically significant (P > 0.05).