Table 2.
In vitro antibiotic activity (MIC, µg/mL) of tetramic acids.a,b
| S1 | S26 | S4 | S2 | E1 | E2 | P1 | P9 | P9B | H3 | H4 | |
| 2ac | 4 | 8 | 8 | 8 | 8 | 8 | 16 | 8 | 32 | 16 | 4 |
| 2bc | 1 | 1 | 1 | 2 | 2 | 4 | 4 | 4 | −d | 2 | 0.5 |
| 2cc | 8 | 8 | 8 | 8 | 8 | 8 | 16 | 8 | 8 | 4 | 0.25 |
| 2dc | 2 | 2 | 2 | 2 | 2 | 2 | 4 | 1 | 4 | 1 | 0.12 |
| 2ec | 2 | 16 | 16 | 16 | 8 | 0.5 | 4 | 1 | 4 | >64 | ≤0.1 |
| 2f | >64 | >64 | >64 | >64 | >64 | >64 | 16 | 8 | 16 | >64 | >64 |
| 2g | 8 | 8 | 8 | 8 | 16 | 8 | 64 | 16 | 8 | 4 | 0.25 |
| 2h | 2 | 2 | 2 | 2 | 2 | 2 | 8 | 4 | >64 | >64 | 8 |
| 3a | >64 | >64 | 32 | >64 | 16 | 16 | 8 | 8 | 8 | >64 | >64 |
| 3b | 4 | 8 | 2 | 8 | 1 | 2 | 0.5 | 0.5 | 0.5 | 8 | 1 |
| 3c | 8 | 32 | 32 | 16 | 8 | 16 | 8 | 8 | 8 | 32 | 4 |
| 3d | 8 | 64 | 32 | 32 | 8 | 16 | 8 | 8 | 4 | 64 | 4 |
| 3e | >64 | >64 | >64 | >64 | >64 | >64 | 64 | 64 | 64 | >64 | 64 |
| 3f | >64 | >64 | >64 | >64 | >64 | >64 | >64 | >64 | >64 | >64 | >64 |
| 1cc | 0.1 | 0.12 | 1 | 64 | ≤0.1 | ≤0.1 | 2 | 2 | 2 | >64 | 0.5 |
| 1d | 8 | 64 | 32 | 64 | 32 | 4 | 64 | 64 | >64 | >64 | 16 |
| Linec | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 0.5 | 0.5 | 16 | 4 |
| Cip | 0.1 | 0.5 | 0.12 | 16 | 1 | 32 | 1 | 1 | 1 | 0.5 | ≤0.1 |
| Amox | −d | −d | −d | −d | −d | −d | >0.03 | 8 | −d | −d | −d |
| Caz | 8 | 16 | 16 | −d | −d | −d | −d | −d | −d | −d | −d |
aAbbreviation; S1; S. aureus 1, ATCC13709 in vivo (methicillin sensitive), S26; S. aureus 26, ATCC25923 (vancomycin susceptible), S4; S. aureus 4, Oxford, S2; S. aureus 2, (MRSA in vivo), E1; E. faecalis 1, ATCC29212 VanS (vancomycin susceptible), E2; E. faecium 1, VanA (vancomycin resistant), P1; S. pneumonia 1, ATCC49619 (erythromycin susceptible), P9; S. pneumonia 9, (multi-drug resistant), P9B; S. pneumonia 9 in presence of 2.5% horse blood, H3; H. influenzae 3, ATCC31517 MMSA, H4; H. influenzae 4, LS2 Efflux knock out, Line; linezolid, Cip; ciprofloxacin, Amox; amoxicillin, Caz; ceftazidime. bAll analogues are inactive (MIC > 64 µg/mL) against E. coli 1, ATCC25922 (non pathogenic strain), E. coli 50, Ec49 No efflux and P. aeruginosa 1, ATCC27853. cThe activity was reported in our previous publication [10]. dNot determined.