28 May 2025

2 minute read

By: Chris Wright

North America

There is considerable variability among Mycoplasma synoviae (MS) isolates in their ability to produce disease and currently only a few virulence factors have been identified. Changes in genes involved in transmissibility, colonization and immunogenicity may alter the virulence of MS strains. The identification of mutations (single nucleotide polymorphisms (SNPs), insertions or deletions) that are linked to increased pathogenicity of MS strains is crucial to the development of more stable and effective vaccines and will also be valuable in predicting the clinical impact of field outbreaks.

Eniope B. Oluwayinka and Naola Ferguson Noel, University of Georgia, USA, carried out in vivo studies to validate the pathogenicity status of MS isolates from commercial poultry farms in USA suspected to be mildly, moderately and very virulent based on in silico analysis of three proteins (ObgE, OppF and GAPDH) previously linked to the pathogenicity of MS strains.

Groups of chickens were inoculated with the MS isolates and air sac and footpad lesions were scored at two weeks post-challenge. Genetic variation analysis of the MS genomes was carried out to identify changes linked to the MS strains determined to be very virulent. Using Illumina technology, full genome libraries were generated following genomic DNA extraction from the MS isolates; contigs for each strain were annotated using a fully annotated MS reference genome.

Different pathotypes of the MS isolates (moderate, mildly and very virulent) were confirmed by the in vivo studies. Seven isolates caused footpad lesions, and five isolates caused airsacculitis, two of which caused severe airsacculitis. A nucleotide change (G to A) in an intergenic space distinguished the two MS isolates that caused severe airsacculitis from three that caused moderate airsacculitis, while an SNP (Ser16Ile) in a mobile element protein with a moderate SNP effect was common in the MS isolates that caused airsacculitis. This study indicates that the pathogenicity of MS isolates may be predicted through in silico analysis of MS genomes.