Biological characterization of RussianMycoplasma gallisepticumfield isolates

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.

Unraveling the Global Phylodynamic and Phylogeographic Expansion of Mycoplasma gallisepticum: Understanding the Origin and Expansion of This Pathogen in Ecuador

Mycoplasma gallisepticum (MG) is among the most significant problems in the poultry industry worldwide, representing a serious threat to international trade. Despite the fact that the mgc2 gene has been widely used for diagnostic and molecular characterization purposes, there is a lack of evidence supporting the reliability of this gene as a marker for molecular epidemiology approaches. Therefore, the current study aimed to assess the accuracy of the mgc2 gene for phylogenetic, phylodynamic, and phylogeographic evaluations. Furthermore, the global phylodynamic expansion of MG is described, and the origin and extension of the outbreak caused by MG in Ecuador were tracked and characterized. The results obtained strongly supported the use of the mgc2 gene as a reliable phylogenetic marker and accurate estimator for the temporal and phylogeographic structure reconstruction of MG. The phylodynamic analysis denoted the failures in the current policies to control MG and highlighted the imperative need to implement more sensitive methodologies of diagnosis and more efficient vaccines. Framed in Ecuador, the present study provides the first piece of evidence of the circulation of virulent field MG strains in Ecuadorian commercial poultry. The findings derived from the current study provide novel and significant insights into the origin, diversification, and evolutionary process of MG globally.

Comparison of Experimental Infection of Normal and Immunosuppressed Chickens with Mycoplasma gallisepticum

Four different models of infection of chickens with Mycoplasma gallisepticum (MG) were evaluated. Normal or immunosuppressed chicks (10 days old) were infected with the MG R_low strain via eye and nasal drops or by direct air sac injection. Bacterial load in the lungs was quantified and air sac and tracheal lesion scores, tracheal mucosal thickness and humoral immune responses were assessed. Serum antibody responses were assessed by use of a serum plate agglutination test. Three days post infection (dpi), all immunosuppressed chicks had developed significant respiratory signs. Chicks infected via air sac injection had significant differences in serum antibody and gross lesion scores at 5 dpi. All chicks had developed pathological changes by 7 dpi. Air sac inoculation of immunosuppressed chicks produced more significant (P ≤0.05) lesions, and these birds had the highest bacterial load in the lungs compared with other groups.

Development and application of a combined molecular and tissue culture-based approach to detect latent infectious laryngotracheitis virus (ILTV) in chickens

Infectious laryngotracheitis virus (ILTV) causes severe respiratory disease in chickens. ILTV can establish latency and reactivate later in life, but there have been few investigations of ILTV latency. This study aimed to contribute to the methodologies available to detect latent ILTV. A nested PCR was developed which was more sensitive than three other molecular methods investigated in this study. This nested PCR was then used in conjunction with in vitro reactivation culture methods that were optimized and applied to trigeminal ganglia (TG) and tracheal samples from ILTV-vaccinated commercial layer birds (n = 30). ILTV DNA was detected by nested PCR in the upper respiratory tract (URT) or eye of 22 birds. Of the remaining 8 birds, ILTV could be detected by co-culture in TG of 5 birds, with reactivated virus mostly detected 6 days post-explant (dpe). ILTV was also detected in tracheal cultures by 6 dpe. In the ILTV-positive URT samples, the virus could be characterised as vaccine strains SA2 (n = 9) or A20 (n = 5). This study provides evidence for reactivation and shedding of vaccine ILTV in commercial layer birds. Moreover, this study produced a molecular and in-vitro culture method to detect latent viral infection.

Presence of DNA extracellular traps but not MUC5AC and MUC5B mucin in mucoid plugs/casts of infectious laryngotracheitis virus (ILTV) infected tracheas of chickens

Although it has been speculated that the tracheal obstructions and asphyxiation during acute infectious laryngotracheitis (ILT) are due to mucoid plugs/casts formed by mucus hypersecretion, there are no reports demonstrating this. Hence, in the present study, we first examined if the main respiratory mucins, MUC5AC and MUC5B, are expressed in the mucosae of larynx, trachea and bronchi of mock-inoculated and ILTV infected chickens. Second, the tracheas with plugs/casts were stained for mucins (MUC5AC and MUC5B) and nuclear material (traps). MUC5AC and MUC5B were produced by the mucosae of larynx, trachea and bronchi of mock-inoculated chickens. Interestingly, MUC5AC and MUC5B were exclusively present in the dorsal tracheal region of the cranial and middle part of trachea of mock-inoculated chickens. In ILTV infected chickens, the tracheal lumen diameter was almost 40% reduced and was associated with a strongly increased tracheal mucosal thickness. MUC5AC and MUC5B were scarcely observed in larynx, trachea and bronchi, and in tracheal plugs/casts of ILTV infected birds. Surprisingly, DNA fibrous structures were observed in connection with nuclei of 10.0±7.3% cells, present in tracheal plugs/casts. Upon inoculation of isolated blood heterophils with ILTV, DNA fibrous structures were observed in 2.0±0.1% nuclei of ILTV inoculated blood heterophils at 24hours post inoculation (hpi). In conclusion, the tracheal obstructions and suffocation of ILTV infected chickens are due to a strong thickening of the mucosa (inflammation) resulting in a reduced tracheal lumen diameter and the presence of mucoid plugs/casts containing stretched long DNA-fibrous structures (traps) but not MUC5AC and MUC5B mucins.