This study compares the antimicrobial susceptibility over time between two groups of Mycoplasma gallisepticum (MG) isolates from the same geographical area. Minimum inhibitory concentration of 13 antimicrobials was determined against two groups of MG isolates from chickens. Group 1 strains (n = 22) were isolated in 2004-2005 while group 2 strains (n = 7) were isolated in 2007-2008. Minimum inhibitory concentration 50 for group 1 versus group 2 was 4/4, 0.5/0.5, ≤0.031/≥64, ≤0.031/2, ≤0.031/0.125, 1/0.5, 1/1, ≤0.031/≤0.031, ≤0.031/2, ≤0.031/2, 1/4, ≤0.031/0.062, and 0.062/2 μg/ml against gentamicin, spectinomycin, erythromycin, tilmicosin, tylosin, florfenicol, thiamphenicol, tiamulin, ciprofloxacin, enrofloxacin, chlortetracycline, doxycycline, and oxytetracycline, respectively. There was a statistically significant increase in resistance of group 2 to erythromycin, tilmicosin, tylosin, ciprofloxacin, enrofloxacin, chlortetracycline, doxycycline, and oxytetracycline. This dramatic increase in resistance against 8 antimicrobials belonging to three different families of antimicrobials in a relatively short period of time appears to be rare and of concern. The cause of this increased resistance observed in group 2 of MG isolates was not determined and should be further investigated. Monitoring of MG field strain susceptibility is highly recommended to implement successful treatment and prophylaxis programs in endemic areas.
Bibliographical noteFunding Information:
We would like to thank the Deanship of Research at Jordan University of Science and Technology and The Scientific Research Support Fund of the Ministry of Higher Education and Scientific Research for supporting this work. We also thank Dr. Kamel Mahmoud for his comments and help with the statistical analysis and Dr. Stephan Thayer for his help in revising this manuscript.
- Minimum inhibitory concentration
- Mycoplasma gallisepticum