Targeted sequencing analysis of Mycoplasma gallisepticum isolates in chicken layer and breeder flocks in Thailand
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Published on: February 20, 2015
Arithat Limsatanun1, Somsak Pakpinyo2, Kriengwich Limpavithayakul2
1Faculty of Veterinary Science, Prince of Songkla University, Hat Yai, Kho Hong, Songkhla, 90110, Thailand. arithat.l@psu.ac.th.
Abstract:
Mycoplasma gallisepticum (MG) is one of the most economically important pathogens worldwide. MG affects the respiratory system and impairs growth performance in poultry. In developing countries, the most widely used technique to identify MG is the conventional PCR assay. In this study, 24 MG isolates collected from Thailand farms with unvaccinated chickens during 2002-2020 were characterized by gene-targeted sequencing (GTS), followed by phylogenetic analysis using unweighted pair group method with arithmetic mean. These 24 Thai MG isolates differed from vaccine strains, including the F, ts-11 and 6/85 strains. One isolate showed 99.5-100% genetic similarity to the F strain with 4 partial gene analyses. This result may have been due to contamination from vaccinated flocks because the F strain is the most commonly used vaccine strain in Thailand. However, the GTS analysis using the partial MG genes in this study showed that the isolates could be grouped into different patterns based on individual gene sequences. The phylogenetic analysis of partial mgc2, gapA, pvpA and lp gene sequences classified the Thai MG isolates into 7, 11, 7 and 2 groups, respectively. In conclusion, at least 2 partial MG genes, especially partial gapA and mgc2 genes, are needed to differentiate MG isolates.
Insights
To effectively identify Mycoplasma gallisepticum (MG) in poultry, utilizing at least two partial genes, particularly gapA and mgc2, is crucial for differentiating isolates. This helps in understanding poultry disease dynamics.
Area of Science:
- Veterinary Microbiology
- Poultry Health
- Molecular Epidemiology
Background:
- Mycoplasma gallisepticum (MG) is a significant poultry pathogen causing respiratory disease and economic losses globally.
- Conventional PCR is widely used for MG identification in developing countries.
- Characterizing local MG strains is essential for effective disease management.
Purpose of the Study:
- To genetically characterize Mycoplasma gallisepticum isolates from Thai poultry farms.
- To evaluate the utility of gene-targeted sequencing (GTS) and phylogenetic analysis for differentiating MG strains.
- To determine the minimum number of genes required for accurate MG isolate classification.
Main Methods:
- Collected 24 MG isolates from unvaccinated Thai chicken farms (2002-2020).
- Performed gene-targeted sequencing (GTS) on partial genes (mgc2, gapA, pvpA, lp).
- Conducted phylogenetic analysis using the unweighted pair group method with arithmetic mean (UPGMA).
Main Results:
- Thai MG isolates showed genetic variations compared to vaccine strains (F, ts-11, 6/85).
- One isolate exhibited high genetic similarity to the F strain, suggesting potential vaccine contamination.
- Phylogenetic analysis revealed distinct groupings based on individual gene sequences: 7 (mgc2), 11 (gapA), 7 (pvpA), and 2 (lp).
Conclusions:
- At least two partial MG genes are necessary for reliable differentiation of isolates.
- Partial gapA and mgc2 genes are particularly effective for classifying Mycoplasma gallisepticum.
- This study provides insights into the genetic diversity of MG in Thailand and aids in diagnostic improvements.
