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Mycoplasma synoviae (n = 26) and M. gallisepticum (n = 11) isolates were gained from 164 clinical samples collected from China, India, Indonesia, Malaysia, Philippines, Republic of Korea and Thailand. Most isolates were from commercial chicken production systems. A method of filtering (0.45 μm) samples immediately after collection was convenient allowing over a week for transit to the laboratory. Minimum inhibitory concentrations (MICs) were characterized by a broth microdilution method to enrofloxacin, difloxacin, oxytetracycline, chlortetracycline, doxycycline, tylosin, tilmicosin, tylvalosin, tiamulin, florfenicol, lincomycin, spectinomycin and lincomycin and spectinomycin combination (1:2). Increased MICs to various antimicrobials were seen in different isolates but appeared largely unrelated to the antimicrobial treatment histories. Overall, the results were similar to other MIC surveys around the world. Generally, low MICs to tetracyclines, tiamulin and tylvalosin were observed. Increased tilmicosin MICs were observed in both M. synoviae and M. gallisepticum isolates (≥64 μg/ml MIC 90 values) and this was seen in all isolates with high tylosin MICs. Increases in lincomycin MICs were mostly associated with increases in tilmicosin MICs. The results also suggested that antimicrobial use after mycoplasma vaccination may interfere with vaccine strain persistence and efficacy (field strains were more commonly observed in flocks that had treatments after vaccination) and this area warrants more investigation. The study shows that isolation and MIC determination can be done from remote locations and suggests that this may provide information that will allow more effective use of antimicrobials or other methods of control of avian mycoplasma in chickens (e.g. live vaccines) and therefore more responsible use of antimicrobials from a one health perspective., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Mycoplasma synoviae is one of the economically most significant avian Mycoplasma species. It can cause great financial losses to the poultry industry by inducing respiratory diseases, infectious synovitis, or eggshell apex abnormalities. There are different approaches to control M. synoviae infection. Although antimicrobial therapy cannot replace long-term solutions, like eradication and vaccination, this strategy can be effective in the short term, as adequate antibiotic treatment can relieve economic losses through the attenuation of clinical signs and reduction of transmission. Using broth microdilution method, minimal inhibitory concentration (MIC) values to fourteen antibiotics related to eight antimicrobial groups were determined in 96 M. synoviae strains. Whole genome sequencing and sequence analysis revealed mutations potentially associated with decreased susceptibility to fluoroquinolones, macrolides and lincomycin. Molecular markers responsible for the high MICs to fluoroquinolones were found in the gyrA, gyrB, parC and parE genes. Besides, single nucleotide polymorphisms identified in genes encoding the 23S rRNA were found to be responsible for high MICs to the 50S inhibitor macrolides and lincomycin, while amino acid change in the 50S ribosomal protein L22 could be associated with decreased susceptibility to macrolides. The revealed mutations can contribute to the extension of knowledge about the genetic background of antibiotic resistance in M. synoviae. Moreover, the explored potentially resistance-related mutations may serve as targets for molecular biological assays providing data of antibiotic susceptibility prior to the laborious and time-consuming isolation of M. synoviae strains., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Monitoring of susceptibility to antibiotics in field isolates of pathogenic avian mycoplasmas is important for appropriate choice of treatment. Our study compared in vitro susceptibility to enrofloxacin and difloxacin in recent (2005-2006) isolates of Mycoplasma gallisepticum and Mycoplasma synoviae from meat-type turkey flocks with archived (1997-2003) isolates and reference strains. Comparison of minimal inhibitory concentration (MIC) values determined by microtest, agar dilution and commercial Etest showed good agreement, but underscored the need for standardized methods for testing. Notably, while the commercial Etest was convenient and accurate for determining MICs for enrofloxacin in the range 0.002-0.094microg/ml, the endpoint of inhibition for M. gallisepticum and M. synoviae strains with MIC values > or =1.0microg/ml could not be determined. A decrease in susceptibility to both fluoroquinolones was detected in archived strains but to a greater degree in recent isolates, most of which had MICs above the NCCLS susceptibility breakpoint for these antibiotics (< or =0.5microg/ml). In contrast, except for one flock, M. synoviae isolates were susceptible, although intrinsically less susceptible than M. gallisepticum. Overall for the 88 strains tested (45 M. gallisepticum, 43 M. synoviae), the MIC50 for both enrofloxacin and difloxacin was 0.5microg/ml. The isolation of fluoroquinolone-resistant M. gallisepticum isolates from breeder and broiler flocks as well as from meat-type turkeys suggests that these strains have become established in Israel, necessitating a reevaluation of antibiotic therapy. Periodic survey of MICs in field isolates of avian mycoplasmas to monitor for the possible appearance of resistant strains is recommended.

Mycoplasma synoviae infection occurs worldwide in commercial poultry flocks and may result in severe economic losses. The prevalence of this mycoplasma in standard layers older than 60 weeks was studied in a French department and the characteristics of infected or free flocks were compared. The genomic profiles of isolates from 36 infected flocks were studied by pulsed-field gel electrophoresis and random amplified polymorphic DNA methods in order to investigate possible routes of transmission. The minimum inhibitory concentrations of antibiotics were determined. Results showed that infection was more frequent in multi-age farms. Egg production and mortality of infected flocks were respectively lower and higher than in non-infected flocks but the differences were not statistically significant. The genomic profiles of isolates were quite homogeneous, a feature which does not facilitate the understanding of routes of transmission. All isolates were susceptible to tetracyclines, macrolides (except erythromycin), spectinomycin and fluoroquinolones.