Table 1.
Minimum inhibitory concentrations (MICs) of S. Typhimurium ATCC 19585 (WT-ST), ciprofloxacin-induced antibiotic-resistant S. Typhimurium ATCC 19585 (CI-ST), and clinically-acquired antibiotic-resistant S. Typhimurium CCARM 8009 (CA-ST) in absence and presence of β-lactamase inhibitors [BLI-489 (BL), clavulanate (CA), sulbactam (SB) or tazobactam (TB)] and efflux pump inhibitors [carbonyl cyanide-m-chlorophenyl hydrazine (CCCP) and phenylalanine-arginine-β-naphthylamide (PaβN)]
| Strain | Antibiotic | Control | β-Lactamase inhibitor | Efflux pump inhibitor | ||||
|---|---|---|---|---|---|---|---|---|
| BL | CA | SB | TB | CCCP | PAβN | |||
| WT-ST | Ampicillin | 4(S) | 1(S) | 2(S) | 1(S) | 2(S) | 4(S) | 4(S) |
| Cefoxitin | 2(S) | 1(S) | 1(S) | 0.5(S) | 1(S) | 2(S) | 2(S) | |
| Ceftriaxone | 0.063(S) | 0.016(S) | 0.031(S) | 0.016(S) | 0.016(S) | 0.063(S) | 0.063(S) | |
| Chloramphenicol | 2(S) | 2(S) | 2(S) | 2(S) | 2(S) | 0.5(S) | 0.5(S) | |
| Ciprofloxacin | 0.016(S) | 0.008(S) | 0.008(S) | 0.008(S) | 0.008(S) | 0.008(S) | 0.008(S) | |
| Levofloxacin | 0.016(S) | 0.008(S) | 0.004(S) | 0.008(S) | 0.008(S) | 0.004(S) | 0.008(S) | |
| Meropenem | 0.031(S) | 0.016(S) | 0.031(S) | 0.008(S) | 0.008(S) | 0.016(S) | 0.016(S) | |
| Tetracyline | 1(S) | 1(S) | 0.5(S) | 0.5(S) | 0.5(S) | 0.25(S) | 0.5(S) | |
| Tobramycin | 4(I) | 0.5(S) | 0.5(S) | 0.5(S) | 0.5(S) | 2(S) | 4(I) | |
| CI-ST | Ampicillin | 8(S) | 4(S) | 8(S) | 2(S) | 4(S) | 8(S) | 8(S) |
| Cefoxitin | 8(R) | 4(I) | 4(I) | 4(I) | 4(I) | 4(I) | 4(I) | |
| Ceftriaxone | 0.5(S) | 0.125(S) | 0.063(S) | 0.25(S) | 0.125(S) | 0.5(S) | 0.5(S) | |
| Chloramphenicol | 8(I) | 8(I) | 8(I) | 8(I) | 8(I) | 4(S) | 4(S) | |
| Ciprofloxacin | 2(R) | 0.25(S) | 0.5(S) | 0.25(S) | 0.5(S) | 0.5(S) | 0.5(S) | |
| Levofloxacin | 0.5(S) | 0.125(S) | 0.25(S) | 0.25(S) | 0.25(S) | 0.125(S) | 0.25(S) | |
| Meropenem | 0.25(S) | 0.125(S) | 0.063(S) | 0.25(S) | 0.125(S) | 0.125(S) | 0.125(S) | |
| Tetracyline | 2(I) | 1(S) | 2(I) | 1(S) | 1(S) | 1(S) | 2(I) | |
| Tobramycin | 8(R) | 4(I) | 8(R) | 8(R) | 4(I) | 4(I) | 8(R) | |
| CA-ST | Ampicillin | > 512(R) | 128(R) | 128(R) | 64(R) | 128(R) | > 512(R) | > 512(R) |
| Cefoxitin | 8(R) | 2(S) | 4(I) | 4(I) | 8(R) | 4(I) | 4(I) | |
| Ceftriaxone | 0.125(S) | 0.063(S) | 0.125(S) | 0.125(S) | 0.125(S) | 0.125(S) | 0.125(S) | |
| Chloramphenicol | 2(S) | 2(S) | 2(S) | 2(S) | 2(S) | 2(S) | 2(S) | |
| Ciprofloxacin | 0.031(S) | 0.008(S) | 0.008(S) | 0.016(S) | 0.008(S) | 0.016(S) | 0.016(S) | |
| Levofloxacin | 0.063(S) | 0.008(S) | 0.031(S) | 0.016(S) | 0.016(S) | 0.016(S) | 0.016(S) | |
| Meropenem | 0.031(S) | 0.016(S) | 0.031(S) | 0.016(S) | 0.031(S) | 0.016(S) | 0.016(S) | |
| Tetracyline | 2(I) | 1(S) | 2(I) | 1(S) | 2(I) | 1(S) | 2(I) | |
| Tobramycin | 4(I) | 2(S) | 2(S) | 2(S) | 4(I) | 2(S) | 4(I) | |
S, I, and R indicate the antibiotic-sensitive, intermediate, and resistant strains, respectively