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.
Mycoplasma gallisepticum (MG) causes respiratory signs and economic losses in the poultry industry. MG vaccination is one of the effective prevention and control measures that have been used around the world. Our previous study demonstrated that chitosan-adjuvanted MG bacterin could effectively reduce pathological lesions induced by MG and that chitosan could be used as an adjuvant in MG bacterin. The present study determining the efficacy of MG bacterins against the Thai MG strain was based on vaccine programs. Seven groups (25 layers/group) were received MG bacterins containing 0.5% chitosan or a commercial bacterin via intramuscular (IM) or intraocular (IO) route at 6 and 10 wk of age. Sham-negative and sham-positive controls were groups 1 and 2, respectively. Group 3: IM route of chitosan bacterin followed by IM route of chitosan bacterin; group 4: commercial bacterin via IM route followed by chitosan bacterin via IO route; group 5: commercial bacterin via IM route followed by commercial bacterin via IM route; group 6: chitosan bacterin via IM followed by chitosan bacterin via IO route; and group 7: chitosan bacterin via IO route followed by chitosan bacterin via IO route were determined. At 16 wk of age, all groups, excluding group 1, were challenged intratracheally with 0.1 mL containing Thai MG strain 107 colony-forming unit. At 17, 18, and 20 wk of age, 5 birds in each group were bled for serological testing and swabbed at the choanal cleft for the quantitative real-time PCR assay, the euthanized and necropsied. The results showed that birds vaccinated with a commercial intramuscular bacterin followed by an intraocularly chitosan adjuvant bacterin showed the best protection against the MG challenge. The study indicated that chitosan could be the effective mucosal adjuvant and increased the effectiveness of MG bacterin.
Mycoplasma gallisepticum (MG) is one of the major pathogens that cause respiratory signs in the poultry industry. To control MG infection, vaccination is the useful procedure. In this study, MG vaccine was developed by using the local Thai MG isolate (AHRL 20/52). Chitosan, a polysaccharide adjuvant derived from crustaceans, has been successfully used in various vaccines. The objectives of this study were to prepare MG bacterins by using chitosan, serving as an adjuvant, to determine protection against the field Thai MG isolate and to evaluate tissue reaction at the injection site. Six groups of 6-wk-old layers (20 birds/group) were intramuscularly vaccinated with bacterin containing various concentrations of chitosan (0.25, 0.5, and 1%), a commercially available MG bacterin, respectively. Sham-negative and sham-positive controls were included in the experiment. Six weeks postvaccination, all groups excluding the negative control were intratracheally challenged with 100 μl of 10 colony-forming units of Thai MG isolate (AHRL 58/46). At 1, 2, 3, and 4 wk postchallenge, five birds from each group were euthanatized and necropsied to determine the gross and histopathologic lesions. For a tissue reaction study, three groups of 24 birds each including sham negative control, 0.5% chitosan bacterin and commercial vaccine were given as previously described. At 1, 2, and 3 wk postvaccination, 8 birds from each group were randomly selected to euthanatize, necropsy, and determine the gross lesions, and 3 out of 8 birds were randomly selected to determine the histopathologic lesions. The results demonstrated that prepared bacterins induced lower numbers of positive antibody birds compared to the commercial vaccine, but groups receiving bacterin containing 0.5 and 1% chitosan exhibited significantly lower tracheal lesions than the positive control and commercial vaccine groups (P < 0.05). Chitosan formulation caused less tissue reaction than the commercial vaccine. These results demonstrated that the prepared MG bacterins could effectively reduce MG-induced pathologic lesions and that chitosan could be used as adjuvant in MG bacterins.
Mycoplasma gallisepticum (MG) is one of the most economically significant pathogens worldwide. MG affects the respiratory system and cause a poor growth performance in poultry. In some developing countries, the conventional PCR assay are still the widely used technique. In this study, 24 collected Thai MG isolates from the unvaccinated farms during 2002-2020 were characterized by gene-targeted sequencing (GTS), followed by phylogenetic using UPMGA analysis. From the results, 24 Thai MG isolates could be differentiated from vaccine strains including F, ts-11 and 6/85. One of Thai MG isolates showed 99.5-100% genetic similarity to F strain with 4 partial genes analysis. The contamination of F strain from the vaccinated farms could be a possible reason because F strain is the most used vaccine strain in Thailand. However, The GTS analysis using the partial MG genes in this study showed that Thai MG isolates were grouped in different patterns based on individual gene sequences. The phylogenetic of partial mgc2, gapA, pvpA and lp gene sequences could classified 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 should be determined to differentiate the MG isolates.
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