Genotyping Mycoplasma hyorhinis by multi-locus sequence typing and multiple-locus variable-number tandem-repeat analysis

Molecular detection and genetic characterization of Mycoplasma gallisepticum and Mycoplasma synoviae in selected chicken breeds in South Africa

BACKGROUND

The impact of chickens on maintaining the economy and livelihood of rural communities cannot be overemphasized. In recent years, mycoplasmosis has become one of the diseases that affect the success of South African chicken production. Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are the most prevalent strains of Mycoplasma in South Africa. MG and MS are significant respiratory pathogens affecting the productivity of chickens. The present study aimed to molecularly detect using qPCR and characterize the presence of MG and MS using phylogenetic analysis. The phylogenetic analysis was utilized to clarify general evolutionary relationships between related taxa of different MG and MS observed in tracheal swabs from South African chicken breeds.

METHODS

Forty-five tracheal swabs of the Lohmann Brown (n = 9), Rhode Island Red (n = 9), Ovambo (n = 9), Venda (n = 9), and Potchefstroom Koekoek (n = 9) breeds were collected from symptomatic chickens present in the commercial farm. To detect MG and MS, DNA was extracted from tracheal swabs and faecal samples, and qPCR was performed with a 16 s rRNA (310 bp) and vlhA (400 bp) gene fragment. Following the sequencing of all the amplicons, MG, and MS dendrograms showing the evolutionary relationships among the five South African chicken breeds and the GeneBank reference population were constructed.

RESULTS

The qPCR revealed the presence of MG and MS in 22% (2/9) of the tracheal swab samples tested for MS only in Rhode Island Red breeds; 66.6% (6/9) and 33% (3/9) of the tested samples in Ovambo breeds; and 11.1% (1/9) and 44.4% (4/9) of the tested samples in Venda breeds. No MG or MS were detected in the Lohmann Brown or Potchefstroom Koekoek breed. Furthermore, qPCR revealed the presence of MG in pooled faecal samples from Lohmann Brown and Ovambo breeds. Eight different bacterial isolates were recognized from both samples. Four isolates were of the 16 s ribosomal ribonucleic acid (rRNA) gene (named PT/MG51/ck/00, PT/MG48/ck/00, PT/MG41/ck/00 and PT/MG71/ck/00) gene of Mycoplasma gallisepticum, and the other was Mycoplasma Synoviae variable lipoprotein hemagglutinin A (vlhA) gene (named PT/MSA22/ck/01, PT/MS41/ck/01, PT/MS74/ck/01 and PT/MS46/ck/01) which were available in GenBank. These isolates were successfully sequenced with 95-100% similarity to the isolates from the gene bank.

CONCLUSION

The study revealed the presence of both MG and MS in the chicken breeds sampled. Furthermore, the different breeds of chicken were found to be susceptible to infection under the intensive or commercial management system. Therefore, continuous surveillance is encouraged to prevent the spread and outbreak of MG and MS in the poultry industry in South Africa.

Epidemiological investigations and multilocus sequence typing of Mycoplasma gallisepticum collected in China

Mycoplasma gallisepticum (MG) is one of the important pathogens in poultry industry and has led to major economic losses. Understanding the epidemiology is crucial to improve the control and eradication program of MG. This study collected 1,250 chicken samples, including trachea and lung, from China in 2022 to investigate the epidemiology of MG. Among the collected samples, 938 samples were positive for MG infection, resulting in an average positive rate of 75.04%. Additionally, 570 samples were positive for both MG and Mycoplasma synoviae (MS) coinfection, with an average positive rate of 45.60%. A total of 183 MG infection positive samples in this study were selected for genotyping, and the multilocus sequence typing (MLST) method based on 7 housekeeping genes was used. As a result, 183 samples belonged to 11 sequence types (STs), with ST-78 being the most prevalent. After BURST analysis, all 183 sequences were divided into group 3. Besides, 119 reference sequences from database and 183 sequences of this study were selected to construct the phylogenetic tree using the neighbor-joining method. The results revealed that the sequences from China, total 196 sequences, were classified into 4 branches. The findings suggest that the MG strains in China exhibit diverse genotypes, which may be related to international trade and the use of live vaccines. Furthermore, we detected the drug susceptibility of 10 isolated strains randomly, which may be helpful to guide the clinical use of drugs to control MG infection.

Establishment of a Mycoplasma hyorhinis challenge model in 5-week-old piglets

Introduction

Mycoplasma hyorhinis is an emerging swine pathogen with high prevalence worldwide. The main lesions caused are arthritis and polyserositis, and the clinical manifestation of the disease may result in significant economic losses due to decreased weight gain and enhanced medical costs. We aimed to compare two challenge routes to induce M. hyorhinis infection using the same clinical isolate.

Methods

Five-week-old, Choice hybrid pigs were inoculated on 2 consecutive days by intravenous route (Group IV-IV) or by intravenous and intraperitoneal routes (Group IV-IP). Mock-infected animals were used as control (control group). After the challenge, the clinical signs were recorded for 28 days, after which the animals were euthanized. Gross pathological and histopathological examinations, PCR detection, isolation, and genotyping of the re-isolated Mycoplasma sp. and culture of bacteria other than Mycoplasma sp. were carried out. The ELISA test was used to detect anti-M. hyorhinis immunoglobulins in the sera of all animals.

Results

Pericarditis and polyarthritis were observed in both challenge groups; however, the serositis was more severe in Group IV-IV. Statistically significant differences were detected between the challenged groups and the control group regarding the average daily weight gain, pathological scores, and ELISA titers. Additionally, histopathological scores in Group IV-IV differed significantly from the scores in the control group. All re-isolated strains were the same or a close genetic variant of the original challenge strain.

Discussion

Our results indicate that both challenge routes are suitable for modeling the disease. However, due to the evoked more severe pathological lesions and the application being similar to the hypothesized natural route of infection in Group IV-IV, the two-dose intravenous challenge is recommended by the authors to induce serositis and arthritis associated with M. hyorhinis infection.

Epidemiological Investigations and Multi-locus Sequence Typing of Mycoplasma synoviae Isolates from Chicken Farms in China

Mycoplasma synoviae (M. synoviae) is an important pathogen in poultry industry and has led to major economic losses. Understanding the epidemiology is crucial to improve control and eradication program of M. synoviae. In this study, 487 samples suspected with M. synoviae infection were collected from August 2020 to June 2021 in China. Among 487 samples, 324 samples were MS positive, the positive rate was 66.53%, and 104 strains were isolated from 324 positive samples. The multilocus sequence typing (MLST) method based on seven housekeeping genes was used to conduct genotyping 104 M. synoviae strains isolated, and the 104 isolates belonged to 8 sequence types (STs) after MLST genotyping, and ST-34 had the highest proportion. After BURST analysis, all 104 isolates were divided into group 12 with other 56 strains isolated from China. Phylogenetic tree constructed by neighbor-joining method showed that nearly all of Chinese isolates (160 isolates) clustered together and separated from other reference isolates (217 isolates) in the PubMLST database. In conclusion, this study suggested that the M. synoviae strains in China were highly similar and independent of abroad strains.

Virulence and Inoculation Route Influence the Consequences of Mycoplasma hyorhinis Infection in Bama Miniature Pigs

Mycoplasma hyorhinis is a widespread pathogen in pig farms worldwide. Although the majority of M. hyorhinis-colonized pigs have no apparent clinical disease, the pathogen can induce diseases such as polyserositis, arthritis, and eustachitis in some cases. To explore the mechanisms for the occurrence of these diseases, we challenged 4 groups of Bama miniature pigs with M. hyorhinis isolated from pigs without clinical symptoms (non-clinical origin [NCO] strain) or with typical clinical symptoms (clinical origin [CO] strain) and investigated the impacts of different strains and inoculation routes (intranasal [IN], intravenous [IV] + intraperitoneal [IP], and IV+IP+IN) on disease induction. Another group of pigs was set as a negative control. Pigs inoculated with the CO strain through a combined intravenous and intraperitoneal (IV+IP) route showed a significant decrease in average daily weight gain (ADWG), serious joint swelling, and lameness compared with the pigs in the negative-control group. Furthermore, this group developed moderate-to-severe pericarditis, pleuritis, peritonitis, and arthritis, as well as high levels of IgG and IgM antibodies. Pigs inoculated IV+IP with the NCO strain developed less marked clinical, pathological changes and a weaker specific antibody response compared with the pigs inoculated with the CO strain. The challenging results of the NCO strain via different routes (IV+IP, IV+IP+IN, and IN) indicated that the combined route (IV+IP) induced the most serious disease compared to the other inoculation routes. Intranasal inoculation induced a smaller decrease in ADWG without obvious polyserositis or arthritis. These data suggest that differences in both strain virulence and inoculation route affect the consequences of M. hyorhinis infection. IMPORTANCE Mycoplasma hyorhinis is a widespread pathogen in pig farms worldwide. The mechanisms or conditions that lead to the occurrence of disease in M. hyorhinis-infected pigs are still unknown. The objective of this study was to evaluate the impact of differences in the virulence of strain and the inoculation route on the consequences of M. hyorhinis infection.

A core genome multilocus sequence typing scheme for Mycoplasma hyorhinis

Mycoplasma (M.) hyorhinis is a commensal and pathobiont residing in the upper respiratory tract in swine and with the ability to spread systemically, mainly causing polyserositis and polyarthritis in nursery pigs. Since little is known on the epidemiology of M. hyorhinis infection, whole genome sequences of 73 strains isolated from pigs in Austria (n = 71) and Germany (n = 2), that have been isolated from clinically affected pigs during routine diagnostics, and publicly available genomes of eight M. hyorhinis strains were analyzed in the presented study. For this purpose, a core genome multi locus sequence typing (cgMLST) scheme encompassing 453 target genes was developed using the Ridom© SeqSphere + software. Results were compared to two previously described conventional MLST schemes and to a core genome single nucleotide polymorphism (cgSNP) analysis approach. Core genome MLST showed high diversity among the M. hyorhinis strains studied and while certain isolates from one farm or a single animal formed cgMLST clusters (≤ 8 allele differences), no isolates with identical allele profiles were identified. In addition, cgMLST had superior discriminatory power (Simpson's ID = 0.995) over conventional MLST (Simpson's ID = 0.952 and 0.985), while demonstrating a lack of congruence between conventional MLST and genome-wide relationship. Core genome SNP results were highly congruent with cgMLST results but lacked in resolution when comparing closely related isolates. Thus, cgMLST is the most suitable method for epidemiological investigations such as outbreak analysis, and to gain insights into M. hyorhinis population structure.

Development of a molecular biological assay for the detection of markers related to decreased susceptibility to macrolides and lincomycin in Mycoplasma hyorhinis

The control of Mycoplasma hyorhinis infection relies mainly on antimicrobial therapy. However, the antibiotic susceptibility testing of the bacteria is usually not performed before applying the treatment, and thus therapeutic failures are not uncommon. In the case of M. hyorhinis, several antibiotic-resistance-related single nucleotide polymorphisms (SNPs) are known but assays for their detection have not been described yet. The aims of the present study were to investigate macrolide- and lincomycin-resistance-related SNPs in Hungarian M. hyorhinis isolates and to develop mismatch amplification mutation assays (MAMA) to detect the identified resistance markers. Minimal inhibitory concentrations (MIC) of different drugs and whole genome sequences of 37 M. hyorhinis isolates were used to find the resistance-related mutations. One MAMA assay was designed to detect the mutation of the 23S rRNA gene at nucleotide position 2058 (Escherichia coli numbering). For further evaluation, the assay was challenged with 17 additional isolates with available MIC data and 15 DNA samples from clinical specimens. The genotypes of the samples were in line with the MIC test results. The developed assay supports the practice of targeted antibiotic usage; hence it may indirectly reduce some bacterial resistance-related public health concerns.