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What to Treat
• Single sick animals?
• In-contact animals?
• Whole groups?
For CBPP Nicholas et al. (2007) demonstrated that treating whole herds with Advocin was effective in eliminating CBPP from a region of Namibia.
Antimicrobials may not be
effective
• Site (s) of the infection
• Mycoplasmastatic effect
• Animal infection too severe – treated too late
• Organism protected by biofilm
• Individual animal treated, but infection spread to others, allowing re-
infection.
•ANTIMICROBIAL RESISTANCE
• But AR is not the only explanation
Antimicrobial effectiveness
Breakpoints
A measure that relates in vitro MIC results to in vivo effect.
i.e. the maximum threshold for predicting successful antimicrobial
treatment.
For Veterinary Mycoplasma Infections breakpoints have not been
determined.
• Therefore the interpretation of Veterinary Mycoplasma MIC results can
not officially be defined into susceptible, intermediate or resistant.
UK Mycoplasma bovis MIC Results
Mycoplasma bovis Antimicrobial sensitivity - Advocin
0
2
4
6
8
10
12
14
16
18
20
<0.06 0.06 0.12 0.25 0.5 1 2 4 8 16 32 64 >64
Antimicrobial conc in ug/ml
Nu
mb
er
of
iso
late
s
0
10
20
30
40
50
60
70
80
90
100
Perc
en
tag
e
MIC
50%
90%
Cumulative MIC
UK Mycoplasma bovis MIC Results
Mycoplasma bovis Antimicrobial sensitivity - Tilmicosin
0
2
4
6
8
10
12
14
16
18
20
<0.06 0.06 0.12 0.25 0.5 1 2 4 8 16 32 64 >64
Antimicrobial conc in ug/ml
Nu
mb
er
of
iso
late
s
0
10
20
30
40
50
60
70
80
90
100
Perc
en
tag
e
MIC
50%
90%
Cumulative MIC
UK Mycoplasma bovis MIC Results
Mycoplasma bovis Antimicrobial sensitivity - Erythromycin
0
2
4
6
8
10
12
14
16
18
20
<0.12 0.12 0.25 0.5 1 2 8 32 >32
Antimicrobial conc in ug/ml
Nu
mb
er
of
iso
late
s
0
10
20
30
40
50
60
70
80
90
100
Perc
en
tag
e
MIC
50%
90%
Cumulative MIC
UK Mycoplasma bovis MIC Results
45 samples (2004-2009) Test for Trend (Cuzick, 1985)
Range MIC50 MIC90
The results for each antimicrobial
are 2-sided p values.
tylosin 0.25->32 32 >32 p=0.407*
tilmicosin 1->32 >32 >32 p<0.001 decreasing trend
lincomycin 0.25->32 8 >32 p=0.010 decreasing trend
clindamycin <0.12->32 8 >32 p=0.001 decreasing trend
erythromycin 32->32 >32 >32 p=0.263
chloramphenicol 0.25-32 8 32 p=0.016 increasing trend
florfenicol 0.5-32 8 32 p=0.229
spectinomycin 2->32 8 >32 p=0.288
oxytetracycline 0.12->32 8 32 p=0.001 increasing trend
danofloxacin 0.12-32 0.25 8 p=0.002 increasing trend
enrofloxacin 0.12->32 0.5 32 p=0.022 increasing trend
marbofloxacin 0.25->32 1 >32 p=0.403*
tulathromycin 0.25->128 2 >128 p=0.381*
Antimicrobial Resistance
• Antimicrobial resistance can be induced in vitro in a few steps by
subculturing at sub-MIC levels.
• Resistance is often the result of single point mutations in a gene.
Fluoroquinolone: Mutation in gyrA, similar to that described for E. coli
- - - - - -
2
5
0 - - - - - - - - -
2
6
0 - - - -
M.
bovis S G A T T C T T C G G T T T A T G A A G C A
NCTC R G A T T C T T C G G T T T A T A A A G C A
400B07 R G A T T C T T C G G T T T A T A A A G C A
420B07 R G A T T T T T C G G T T T A T G A A G C A
Tylosin >8 µg/ml and Tilmicosin 32 µg/ml had mutations in 23S rRNA
consistent with antimicrobial resistance.
Lerner et al. Vet Micro. In press
Treatment
• Chemotherapy/antimicrobial treatment should be last resort.
• A diagnosis and understanding of pharmacokinetics and
pharmacodynamics is beneficial,
however a lot of this knowledge has been obtained by the
pharmaceutical companies - read the bottle / instructions.
• An awareness of the current antimicrobial resistance status will help in
selecting an effective treatment.
Mycoplasma bovis: Silent and Deadly – The Enemy
• Many Mycoplasma species can be detected in cattle, some causing serious
disease.
• Prevention is easier than cure
Summary
Mycoplasma bovis can enter the herd unnoticed, silent and
ready to attack……
• The organisms are fastidious, but cunning with an armoury of defences
• Diagnostic testing before introducing new stock can prevent infection
• Accurate diagnosis and strategic early treatment with effective antimicrobials
may reduce the impact of this disease invasion
Mycoplasma bovis: Silent and Deadly – The Enemy
THANK YOU
FOR LISTENING AND FOR INVITING ME
