Table 2.
Cysteamine activity against a panel of M. abscessus strains, synergy with the clinically relevant antibiotics, amikacin and azithromycin is demonstrated by chequerboard experiments and calculation of fractional inhibitory concentration index (FICI).
| MIC100 |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Strain | Cysteamine [μg/ml] | Meropenem [μg/ml] | Amikacin [μg/ml] | Azithromycin [μg/ml] | Meropenem/cysteamine (FICI) | Amikacin/cysteamine (FICI) | Azithromycin/cysteamine (FICI) | |||
| DSM44196 (type) | 62 · 5–125 | 64 | 4–8 | 1–2 | 32–64/62 · 5 (1 · 5–2) | Neutral | 1–4/15 · 625–62 · 5 (0 · 5–0 · 75) | Additive | 0 · 25/15 · 625 (0 · 25–0 · 5) | Synergy |
| MR313292 (clinical) | 125–250 | 16–64 | 4 | 8 | 32–64/250 (2–2 · 5) | Neutral-antagonistic | < 1/< 15 · 125–31 · 25 (0 · 375) | Synergy | 4–8/250 (1 · 25–2) | Neutral |
| MR27419N (clinical) | 125 | 64 | 16 | 1 | 64/125 (2) | Neutral | 4/62 · 5 (0 · 75) | Additive | 0 · 25/< 15 · 625 (0 · 375) | Synergy |
| MR313367D (clinical) | 62 · 5–125 | 16–64 | 16 | 1 | 64/125 (2–5) | Neutral-antagonistic | 4/15 · 625–31 · 25 (0 · 5) | Synergy | 0 · 25/15 · 625 (0 · 375–0 · 5) | Synergy |
All results are presented represent the mean of triplicate samples from experiments conducted three times.
Values shown in the table are MIC100. Where antibiotics have been used in combination, the unhighlighted figures show the MIC100 range for each antibiotic, and the figures highlighted in bold are the fractional inhibitory concentration index (FICI) range. Values ≤ 0.5 are interpreted as synergy.