Tiamulin has been reported to possess good activity in vitro against App.
Pijpers in Holland indicated that the MIC90 for a group of 20 Dutch field isolates of App to tiamulin was 8.0µg/ml which compared with <32.0µg/ml for lincomycin and 16.0µg/ml for tylosin [?]. (See following table.)
| HOLLAND |
Pijpers, A. and others (1989) |
| MICs of three antibacterial agents against 20 Dutch clinical isolates of App (15x serotype 9, 5 & serotype 2) |
| Antimicrobial |
MIC range
|
MIC50 (µg/ml)
|
MIC90 (µg/ml)
|
| Tiamutin® (tiamulin) |
4 - 16
|
8
|
8
|
| Lincomycin |
4 - ≤ 32
|
32
|
≤ 32
|
| Tylosin |
8 - 32
|
16
|
16
|
|
Fodor, Stipkovits and Klein (2004) reported from Hungary that the MIC90’s for ten Hungarian field isolates of App to tiamulin were lower than those for tylosin, lincomycin and CTC and ranged from 2.0 - 4.0µg/ml [?]. (See following table.)
| HUNGARY |
Fodor, L., Stipkovits, L. and Klein, U. (2004) |
| MICs (µg/ml) of various antimicrobials against ten Hungarian field isolates of Actinobacillus pleuropneumoniae |
| Antimicrobial |
MIC mean
|
MIC range
|
MIC50
|
MIC90
|
| Doxycycline |
0.43
|
0.25 - 8.0
|
0.25
|
1.0
|
| Chlortetracycline |
6.96
|
1.0 - 32.0
|
8.0
|
32.0
|
| Tylosin |
12.1
|
24.0 - 32.0
|
16.0
|
32.0
|
| Tilmicosin |
1.31
|
90.5 - 2.0
|
2.0
|
2.0
|
| Lincomycin |
5.65
|
1.0 - 16.0
|
8.0
|
16.0
|
| Tiamutin® (tiamulin) |
2.29
|
2.0 - 4.0
|
2.0
|
4.0
|
|
Casals and others (1990) reported on a suggested ‘break point’ scheme to classify the sensitivity to Tiamutin of App, according to the MIC values and achievable lung concentrations. Thus:
- App isolates with MIC values of up to 8.0µg/ml are considered “fully sensitive” to Tiamutin
- App isolates with MIC values of 8.0 - 16.0µg/ml are considered “moderately sensitive”
- App isolates with MIC values >16.0µg/ml are considered “resistant”.
Tiamutin, administered both parenterally and orally accumulates in lung tissue in preference to serum since it is a highly lipophilic, weak base (pKa 7.6). (See section on Pharmacokinetics)
| 
