Molecular characterization and antimicrobial susceptibility profiles of Thai Mycoplasma synoviae isolates

Abstract

Mycoplasma synoviae (MS) infection is mainly controlled by pathogen-free flocks' maintenance, medication in infected flocks, and vaccination in high-risk flocks. The effective control strategy requires convenient approach for detecting and differentiating MS strains and reliable drug susceptible evidence for deciding on reasonable antimicrobial usage. This study aimed to characterize the partial vlhA gene of nine Thai MS isolates circulated in chickens in 2020, to verify the PCR-RFLP assay for strain differentiation, and to determine the eight antimicrobial susceptibility profiles using microbroth dilution method. Based on sequence analysis of the partial vlhA gene, Thai MS isolates in 2020 were classified as types E and L with 19 and 35 amino acid lengths, respectively. The developed PCR-RFLP assay could detect and differentiate vaccine and Thai field strains. Most Thai MS isolates in this study were susceptible to tylosin, tylvalosin, tiamulin, doxycycline, oxytetracycline, tilmicosin, and lincomycin-spectinomycin at MIC₅₀ values of 0.0391, 0.0098, 0.0781, 0.1563, 0.1563, 0.625 and 0.625 μg/mL, respectively; and resistance to enrofloxacin at MIC₅₀ value of 10 μg/mL. In conclusion, this study revealed diagnostic assays for differentiating MS strains and the antimicrobial susceptibility profiles of Thai MS, which are necessary to design suitable MS control procedures for poultry flocks.

Figure 1

Electrophoresis gel demonstrating PCR products from M. synoviae isolates consisting of the full length of partial vlhA gene amplicons size of 350–400 bp (a, b) and the two digested fragments of partial vlhA gene amplicons size of 100–200 bp (c, d). Lane 1 and 17, 1000 bp DNA ladder; Lane 2 and 18, M. gallisepticum S6 strain as negative control; Lane 3 and 19, M. synoviae WVU 1853 strain as positive control; Lane 4, M. synoviae MS-1 strain; Lane 5, AHRU2020CK0615; Lane 6, AHRU2020CK0301; Lane 7, AHRU2020CK0305; Lane 8, AHRU2020CK0404; Lane 9, AHRU2020CK0709; Lane 10, AHRU2020CU1401; Lane 11, AHRU2020CU1409; Lane 12, AHRU2020CU1505; Lane 13, AHRU2015CU2802; Lane 14, AHRU2018CK0301; Lane 15, AHRU2020CU1104; Lane 16, AHRU2020CU1101; Lane 20, M. synoviae MS-H vaccine strain; Lane 21, AHRU2020CU1323; Lane 22, AHRU2020CK1206.

Figure 2

Bar charts illustrate the distribution of M. synoviae isolates among the final MIC values of tested antibiotics, including enrofloxacin, doxycycline, oxytetracycline, tylosin, tilmicosin, tylvalosin, lincomycin-spectinomycin, and tiamulin.