M. hyosynoviae infection - antimicrobial activity of Tiamutin® (tiamulin)
M. hyosynoviae is particularly susceptible in vitro to tiamulin. Studies from Denmark[?], Hungary[?] and U.K.[?] reported the following comparative MIC data on various antimicrobials.
MIC's (mcg/ml) of various antimicrobials against Danish M. hyosynoviae field strains (n=6)
Friis, N.F. and Szancer, J. (1994)
Antimicrobial
MIC50
MIC Final
Initial
Final
Range
Mean
Type S16
Tetracycline
0.25
1.0
0.25 - 2.5
1.2
0.25
Lincomycin
0.05
0.5
0.25 - 1.0
0.6
0.5
Tylosin
0.025
0.05
0.025 - 2.5
0.9
0.05
Tiamutin® (tiamulin)
0.0025
0.025
0.01 - 0.05
0.03
0.025
MIC range, MIC50 and MIC90 (mcg/ml) of tested antibiotics for M. hyosynoviae
Stipkovits, L. and others (2004)
Antimicrobial
MIC range
MIC50
MIC90
Doxycycline
0.25 - 4.0
1.0
2.0
Tylosin
2.0-32.0
4.0
16.0
Lincomycin
0.5 - 8.0
2.0
4.0
Chlortetracycline
8.0 - 32.0
8.0
32.0
Tilmicosin
2.0 - 32.0
4.0
16.0
Tiamutin® (tiamulin)
0.03 - 0.25
0.125
0.25
(No. of strains tested = 10)
Hannan, P.C.T. and others[?] reported on the comparative in vitro activity of tiamulin and the fluoroquinolone enrofloxacin against 7 strains of M. hyosynoviae.
Comparative in vitro activity of tiamulin and the fluoroquinolone enrofloxacin against 7 strains of M. hyosynoviae
MIC range (mcg/ml)
Tiamutin® (tiamulin)
0.0025 - 0.005
Enrofloxacin
0.05 - 0.1
Relative potency of tiamulin/enrofloxacin
20x
Thus in three independent laboratory investigations tiamulin was shown to have exceptional potency against M. hyosynoviae.
Tiamutin was found to be effective against tylosin-resistant M. hyosynoviae.
In an additional study from Denmark[?], the emergence of strains of M. hyosynoviae resistant to tylosin was reported. In isolates from 1995-1996 9/21 were highly susceptible to tylosin whilst 12/21 (57.1%) were resistant to tylosin.
Tiamulin was active against all 21 strains, including those resistant to tylosin.
The authors concluded that resistance to tylosin amongst Danish M. hyosynoviae isolates had emerged and that this antibiotic could therefore no longer be recommended in Denmark for the treatment of M. hyosynoviae infections.
