Table 1.
Antimicrobial activities of four avermectins against bacterial species, including multidrug-resistant M. tuberculosis clinical isolatesa
| Species | Strainb | Drug resistance profilec |
In vitro MIC90 (μg/ml) for: |
|||
|---|---|---|---|---|---|---|
| Ivermectin | Selamectin | Moxidectin | Doramectind | |||
| Escherichia coli | O157:H7 | WT | >256 | >256 | >256 | >256 |
| Acinetobacter baumannii | ATCC 1960 | WT | >256 | >256 | >256 | >256 |
| Pseudomonas aeruginosa | PA01 (H103) | WT | >256 | >256 | >256 | >256 |
| S. lividans | 1326 | WT | >256 | >256 | >256 | >256 |
| R. jostii | RHA1 | WT | >256 | >256 | >256 | >256 |
| Kocuria rhizophila | WT | >256 | >256 | >256 | >256 | |
| Staphylococcus aureus | ATCC 25923 | WT | >256 | >256 | >256 | >256 |
| M. smegmatis | mc2155 | WT | 8 | 4 | 4 | 128 |
| M. avium | ATCC 25291 | WT | >128 | 16 | >128 | >128 |
| M. bovis | BCG Pasteur | WT | 4 | 4 | 4 | 8 |
| M. tuberculosis | H37Rv | WT | 6 | 3 | 3 | 8 |
| M. tuberculosis | CDC 1551 | WT | 4–8 | 1 | 2 | 4–8 |
| M. tuberculosis | Erdman | WT | 8 | 2 | 2–4 | 8 |
| M. tuberculosis | 1254 | 8 | 2–4 | 4 | 8–16 | |
| M. tuberculosis | H37Rv mc24977 | INH | 6 | 1.5 | 3 | ND |
| M. tuberculosis | CI5447 | INH | 1.5 | 1.5 | 0.8–1.5 | ND |
| M. tuberculosis | CI5297 | INH | 6 | 3 | 6 | ND |
| M. tuberculosis | CI5305 | INH | 3 | 1.5 | 1.5 | ND |
| M. tuberculosis | H37Rv mc25857 | INH, RIF | 3 | 1.5 | 3 | ND |
| M. tuberculosis | H37Rv mc25858 | INH, RIF | 3 | 1.5 | 3 | ND |
| M. tuberculosis | V2475 | INH, RIF | 1.5 | 1.5 | 3 | ND |
| M. tuberculosis | CI5058 | INH, RIF | 6 | 6 | 6 | ND |
| M. tuberculosis | CI5324 | INH, RIF | 6 | 3 | 3 | ND |
| M. tuberculosis | CI5400 | INH, RIF | 3 | 3 | 3 | ND |
| M. tuberculosis | CI5072 | INH, RIF, SM | >24 | 3–6 | 3 | ND |
| M. tuberculosis | CI5358 | INH, EMB, ETH | 3 | 1.5 | 3 | ND |
| M. tuberculosis | CI5459 | INH, EMB, ETH | 3 | 1.5–3 | 1.5 | ND |
| M. tuberculosis | CI12081 | INH, RIF, SM, EMB, ETH | >24 | 3 | 3 | ND |
| M. tuberculosis | KZN11 | INH, RIF, SM, EMB | 3 | 3 | 3 | ND |
| M. tuberculosis | KZN5 | INH, RIF, SM, EMB, ETH, KM, PZA | 6 | 3 | 3 | ND |
| M. tuberculosis | KZN6 | INH, RIF, SM, EMB, ETH, KM, PZA | 6 | 6 | 3 | ND |
| M. tuberculosis | KZN12 | INH, RIF, SM, EMB, ETH, KM, PZA | 3 | 3 | 1.5 | ND |
| M. tuberculosis | KZN14 | INH, RIF, SM, EMB, ETH, KM, PZA | 6–12 | 6 | 3–6 | ND |
| M. tuberculosis | KZN15 | INH, RIF, SM, EMB, ETH, KM, PZA | 6 | 3 | 3 | ND |
| M. tuberculosis | KZN16 | INH, RIF, SM, EMB, ETH, KM, PZA | 3 | 1.5 | 1.5 | ND |
| M. tuberculosis | BC-DS1 | 4–16 | 2 | 4 | ND | |
| M. tuberculosis | BC-DS3 | 8–16 | 1–2 | 2 | ND | |
| M. tuberculosis | BC-DS4 | 64 (8) | 1–2 | 2 | ND | |
| M. tuberculosis | BC-DS5 | >128 (8) | 2–4 | 2–4 | ND | |
| M. tuberculosis | BC-MDR2 | INH, RIF, PZA, SM, RBT | >128 (8) | 2 | 2–4 | ND |
| M. tuberculosis | BC-MDR3 | INH, RIF, RBT | 1–2 | 0.5–1 | 1–2 | ND |
| M. tuberculosis | BC-MDR4 | INH, RIF, EMB, PZA, RBT | 4–16 | 2 | 2–4 | ND |
| M. tuberculosis | BC-MDR5 | INH, RIF, PZA, SM, PAS, RBT | 4–16 | 2 | 2–4 | ND |
Mycobacterial strains were assayed in liquid 7H9 media containing 0.2% glycerol and 10% albumin-dextrose-saline. Nonmycobacterial strains were assayed in LB medium. The MTT assay was used to determine the concentration that inhibited growth by 90%. Values in parentheses indicate 50% growth inhibition (MIC50). The M. smegmatis strain was incubated for 3 days, the M. avium, M. bovis BCG, and M. tuberculosis strains were incubated for 7 days, and the nonmycobacterial strains were incubated overnight before the addition of MTT.
Strains V2475 and 1254 have been described previously (10, 11). CI strains are clinical isolates from Mexico. KZN strains are clinical isolates from KwaZulu-Natal, South Africa. BC strains are clinical isolates from British Columbia, Canada.
WT, wild type (no resistance mutations); EMB, ethambutol; ETH, ethionamide; INH, isoniazid; KM, kanamycin; RBT, rifabutin; RIF; rifampin; PAS, p-amino salicylate; PZA, pyrazinamide; SM, streptomycin.
ND, not determined.