Mycoplasma infection continues to be an important cause of loss in poultry production. Kleven (1990) described the losses due to Mycoplasma gallisepticum (MG). These were a reduction in egg production of 10-20%, an increase in embryo mortality and chick mortality of 5-10% and a reduction in weight gain and feed conversion efficiency of 10-20%. In spite of the availability of vaccines, antimicrobial use continues to be the most economic method (Stipkovits et al, 1993) of controlling these infections, where the diseases are still endemic.
As a result, resistance has developed to a number of antimicrobials and the purpose of this paper is to review the activity of tiamulin and several antimicrobials against a number of common pathogenic poultry mycoplasma, MG, M. synoviae (MS), M. meleagridis (MM) and M. iowae (MI) and compare their resistance development over the last 25 years.
Materials and Methods:
A search of published literature was carried out and these data was combined with our own internal reports. A total of 20 references were compiled. Reports from 1975-1989 and from 1990-2000 were compared. The ranges of minimum inhibitory concentrations (MICs) of various antimicrobials against various mycoplasma species were entered into a database. The maximum and minimum data for each time period were compared for tiamulin, tylosin, oxytetracycline, lincomycin and enrofloxacin.
From the 20 references and reports, 13 were from before 1990 and seven from 1990 and after. There was information on 241 isolates of MG, 105 of MS, 28 of MM and 111 of MI. The comparative data for the four mycoplasma species are summarized in the tables below.
Table 1. Mycoplasma gallisepticum, MIC ranges (µg/ml) by time period (no. of isolates)
Table 2. Mycoplasma synoviae, MIC ranges (µg/ml) by time period (no. of isolates)
Table 3. Mycoplasma meleagridis, MIC ranges (µg/ml) by time period (no. of isolates)
Table 4. Mycoplasma iowae, MIC ranges (µg/ml) by time period (no. of isolates)
MG has shown no resistance development to tiamulin over the last 25 years and all 241 isolates could be considered sensitive. In contrast there is resistance development to tylosin, oxytetracycline, lincomycin and borderline resistance to enrofloxacin and this appears to have increased in the last decade.
MS has shown no increase in resistance to tiamulin and almost all of the 105 isolates would be considered sensitive. In contrast, resistance has developed to tylosin and oxytetracycline. Levels of resistance to lincomycin remain low and all strains could be considered sensitive to enrofloxacin.
MM isolates (28) from turkeys show some resistance to tiamulin and enrofloxacin. However, tylosin, oxytetracycline and lincomycin show a marked increase in resistance development.
MI has developed almost no resistance to tiamulin and enrofloxacin. In the nineties all isolates would be considered sensitive. High levels of resistance have developed to tylosin, oxytetracycline and lincomycin.
These findings confirm those of Drews and others (1975) and Stipkovits and Burch (1993) that tiamulin is a low inducer of resistance in mycoplasma in comparison with tylosin and slower than oxytetracycline and enrofloxacin (Stipkovits and Burch, 1993) as resistance has not developed with long-term use. Furthermore, the highest MIC level of tiamulin against MG in recent years is 16 times lower than that of lincomycin.
In conclusion, tiamulin could be considered a highly effective therapeutic in mycoplasma control programs for both chickens and turkeys.
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Stipkovits, L., Laber, G. and Burch, D.G.S. (1993) Comparative studies on efficacy of MG bacterin and tiamulin treatment of breeder layers. Proceedings Xth World Veterinary Poultry Association Congress, Sydney, p155, Abst 40
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Jordan, F.T.W. and Knight, D. (1984) The minimum inhibitory concentration of kitasmycin, tylosin and tiamulin for Mycoplasma gallisepticum and their protective effect on infected chicks. Avian Pathology, 13 pp151-162
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Stipkovits, L. and Burch, D.G.S. (1993) Antibiotic resistance of mycoplasmas of chickens and turkey origin. Proceedings Xth World Veterinary Poultry Association Congress, Sydney, pp17, 9, 121
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Stipkovits, L. (1998) Report to Biochemie ‘Comparative in vitro studies of the efficacy of antibiotics against freshly isolated Mycoplasma iowae strains isolated from turkeys’
Jordan, F.T.W., Forrester, C.A., Ripley, P.H. and Burch, D.G.S. (1998) In vitro and in vivo comparisons of valnemulin, tiamulin, enrofloxacin and lincomycin/spectinomycin against Mycoplasma gallisepticum. Avian Diseases. 42, pp738-745
Gautier-Bouchardon, A.V. Boscher, L., Kempt, I. and Kobisch, M. (1999) Concentrations minimales inhibitrice de 6 antibiotiques vis-a-vis 15 souches de mycoplasmes aviaires. La Recherche Avicole, St. Malo, 23-25 Mars 1999
Poultry technical papers on-line: index
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