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Evaluation of Minimum Inhibitory Concentrations for 154 Mycoplasma synoviae isolates from Italy collected during
Salvatore Catania1, Marco Bottinelli1, Alice Fincato1
1Istituto Zooprofilattico Sperimentale delle Venezie, viale Dell'Università 10, Legnaro (PD), Italy.
Abstract:
Mycoplasma synoviae (MS) is a highly prevalent bacterial species in poultry causing disease and severe economic losses. Antibiotic treatment is one of the control strategies that can be applied to contain clinical outbreaks in MS-free flocks, especially because this bacterium can be transmitted in ovo. It becomes, then, very important for veterinarians to know the antibiotic susceptibility of the circulating strains in order to choose the most appropriate first-line antibiotic molecule as a proactive role in fighting antibiotic resistance. We evaluated the Minimum Inhibitory Concentrations (MICs) of enrofloxacin, oxytetracycline, doxycycline, erythromycin, tylosin, tilmicosin, spiramycin, tiamulin, florfenicol and lincomycin for MS isolates collected between 2012 and 2017 in Italy. A total of 154 MS isolates from different poultry commercial categories (broiler, layer, and turkey sectors) was tested using commercial MIC plates. All MS isolates showed very high MIC values of erythromycin (MIC90 ≥8 μg/mL) and enrofloxacin (MIC90 ≥16 μg/mL). MIC values of doxycycline and oxytetracycline obtained were superimposable to each other with only a one-fold dilution difference. Discrepancies between MIC values of tylosin and tilmicosin were observed. Interestingly, seven isolates showed very high MIC values of lincomycin and tilmicosin, but not all of them showed very high MIC values of tylosin. Most of the MS isolates showed low MIC values of spiramycin, but seven strains showed a MIC ≥16 μg/mL. In the observation period, the frequency of the different MIC classes varied dependently on the tested antibiotic. Interestingly, tilmicosin MICs clearly showed a time-dependent progressive shift towards high-concentration classes, indicative of an on-going selection process among MS isolates. Until standardized breakpoints become available to facilitate data interpretation, it will be fundamental to continue studying MIC value fluctuations in the meantime in order to create a significant database that would facilitate veterinarians in selecting the proper drug for treating this impactful Mycoplasma.
Insights
Antibiotic resistance in Mycoplasma synoviae (MS) is a growing concern in poultry. This study found high resistance to erythromycin and enrofloxacin, with concerning trends for tilmicosin, impacting treatment choices.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Poultry Health
Background:
- Mycoplasma synoviae (MS) causes significant economic losses in poultry.
- In ovo transmission necessitates effective antibiotic control strategies.
- Understanding antibiotic susceptibility is crucial for combating resistance.
Purpose of the Study:
- To evaluate the Minimum Inhibitory Concentrations (MICs) of various antibiotics against Italian MS isolates.
- To identify trends in antibiotic resistance over a five-year period (2012-2017).
- To inform veterinary decisions for effective MS treatment and resistance management.
Main Methods:
- Testing of 154 MS isolates from diverse poultry sectors (broiler, layer, turkey).
- Utilized commercial MIC plates for antibiotic susceptibility testing.
- Evaluated MICs for enrofloxacin, oxytetracycline, doxycycline, erythromycin, tylosin, tilmicosin, spiramycin, tiamulin, florfenicol, and lincomycin.
Main Results:
- High MIC values observed for erythromycin (MIC90 ≥8 μg/mL) and enrofloxacin (MIC90 ≥16 μg/mL).
- Tilmicosin MICs showed a time-dependent shift towards higher concentrations, indicating selection pressure.
- Varied susceptibility patterns observed for lincomycin, tilmicosin, and spiramycin.
Conclusions:
- MS isolates in Italy exhibit significant resistance to erythromycin and enrofloxacin.
- Emerging resistance trends, particularly with tilmicosin, require ongoing monitoring.
- Continued surveillance of MIC fluctuations is essential for guiding veterinary treatment strategies against MS.
