Molecular characterization of MG isolates using RAPD and PFGE isolated from chickens in Brazil

Targeted sequencing analysis of Mycoplasma gallisepticum isolates in chicken layer and breeder flocks in Thailand

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.

Clonal dissemination of antibiotic resistance among Tunisian Mycoplasma gallisepticum isolates as revealed by gene-targeted sequencing analysis

SummaryTo date, very little is known about avian mycoplasma infections in Tunisia. Mycoplasma gallisepticum is one of the most economically significant pathogen for poultry in Tunisia and worldwide. Based on the paucity of data regarding the genetic profiles and antibacterial behavior of M. gallisepticum strains in Tunisia, the present study was conducted. Genetic typing and phylogenetic relationships of 40 M. gallisepticum strains (20 Tunisian isolates, 19 international strains collection, and S6 reference strain) were investigated by gene-targeted sequencing (GTS) using 4 loci ( pvpA , mgc2 , vlhA and the InterGenic Spacer Region (IGSR) between the 16S and the 23S rRNA genes). GTS reveals 12 STs that were found to spread over 2 clonal complexes (CC) and 5 singletons.Emergence of enrofloxacin and spiramycin resistance among M. gallisepticum local isolates have been revealed using the broth microdilution method. Causal mutations have been identified by sequencing the quinolone-resistance determining region (QRDR) and domain II and V of 23S rRNA as well as the rplD and rplV genes for enrofloxacine- and macrolide-resistant isolates, respectively. The emersion of antibiotic resistance to enrofloxacin and spiramycin has been identified as being related to a distinctive clonal complex formed by 4 different STs (ST2, ST3, ST4 and ST5) which would suggest that this phenotype was clonally disseminated.

Comparison of multiple genes and 16S-23S rRNA intergenic space region for their capacity in high resolution melt curve analysis to differentiate Mycoplasma gallisepticum vaccine strain ts-11 from field strains

Mycoplasma gallisepticum (MG) is an important avian pathogen causing significant economic losses in the global poultry industry. In an attempt to compare and evaluate existing genotyping methods for differentiation of MG strains/isolates, high resolution melt (HRM) curve analysis was applied to 5 different PCR methods targeting vlhA, pvpA, gapA, mgc2 genes and 16S-23S rRNA intergenic space region (IGSR). To assess the discriminatory power of PCR-HRM of examined genes and IGSR, MG strains ts-11, F, 6/85 and S6, and, initially, 8 field isolates were tested. All MG strains/isolates were differentiated using PCR-HRM curve analysis and genotype confidence percentage (GCP) values of vlhA and pvpA genes, while only 0, 3 and 4 out of 12 MG strains/isolates were differentiated using gapA, mgc2 genes and IGSR, respectively. The HRM curve analysis of vlhA and pvpA genes was found to be highly correlated with the genetic diversity of the targeted genes confirmed by sequence analysis of amplicons generated from MG strains. The potential of the vlhA and pvpA genes was also demonstrated for genotyping of 12 additional MG strains from Europe and the USA. Results from this study provide a direct comparison between genes previously used in sequencing-based genotyping methods for MG strain identification and highlight the usefulness of vlhA and pvpA HRM curve analyses as rapid and reliable tools specially for diagnosis and differentiation of MG strains used here.

Differentiation of Mycoplasma gallisepticum strains using PCR and high-resolution melting curve analysis

Mycoplasma gallisepticum (MG) is an economically important pathogen of poultry worldwide, causing chronic respiratory disease in chickens and turkeys. Differentiation of MG strains is critical, especially in countries where poultry flocks are vaccinated with live vaccines. In this study, oligonucleotide primers were designed based on a region preceding the trinucleotide repeat of a member of the vlhA gene family, and amplicons of 145-352 bp were generated from cultures of 10 different MG strains, including the ts-11, F and 6/85 vaccine strains. High-resolution melting (HRM) curve analysis of the resultant amplicons could differentiate all MG strains. Analysis of the nucleotide sequences of the amplicons from each strain revealed that each melting curve profile related to a unique DNA sequence. The HRM curve profiles (for ts-11) remained consistent after at least five passages under laboratory conditions. PCR-HRM curve analysis of 33 DNA extracts derived from respiratory swabs, or mycoplasma cultures grown from respiratory swabs, of ts-11-vaccinated commercial or specific pathogen-free chickens identified all these specimens, according to their sequences, as ts-11. The potential of the PCR-HRM curve analysis was also shown in the genotyping of 30 additional MG isolates from Europe, the USA and Israel. The results presented in this study indicate that PCR followed by HRM curve analysis provides a rapid and robust technique for genotyping of MG isolates/strains using both MG cultures and clinical swabs.

Mycoplasma insons sp. nov., a twisted mycoplasma from green iguanas (Iguana iguana)

Mycoplasma insons sp. nov., first cultured from the choanae and tracheae of healthy green iguanas (Iguana iguana) from El Salvador, was readily distinguished from all previously described mollicutes and assigned to the Mycoplasma fastidiosum phylogenetic cluster by 16S rRNA gene sequence comparisons. Growth inhibition assays distinguished the isolates serologically from the other two members of that cluster. Many M. insons cells exhibit a remarkable twisted rod morphology despite lacking a cell wall. The organism is nonmotile, produces acid from glucose, but does not hydrolyze arginine, esculin, or urea. Mycoplasma insons 16S rRNA gene was also detected by PCR in packed blood cells from culture-negative iguanas. The type strain I17P1(T) has been deposited with the Mollicutes Collection at Purdue University and with the American Type Culture Collection (ATCC BAA-1435) in the USA. A limited number of cultures generated by the authors have also been deposited with the Culture Collection, University of Göteborg, in Sweden (CCUG 53461).