Phylogenetic analysis of Mycoplasma suis isolates based on 16S rRNA gene sequence in China

Haemotrophic Mycoplasmas Infecting Pigs: A Review of the Current Knowledge

Haemotrophic mycoplasmas (haemoplasmas) are a group of highly specific and adapted bacteria. Three different haemoplasma species in pigs are known to date: Mycoplasma (M.) suis, M. parvum and 'Candidatus (Ca.) M. haemosuis'. Even though these bacteria have been known in pig farming for a long time, it is difficult to draw general conclusions about the relevance of their infections in pigs. This review summarizes the current knowledge on the three porcine haemoplasma species with regards to clinical and pathological descriptions, pathobiology, epidemiology and diagnostics as well as prevention and therapy. Overall, it is clear that considerably more data are available for M. suis than for the other two species, but generally, porcine haemoplasmas were found to be highly prevalent all over the world. Mycoplasma suis is the most virulent species, causing acute infectious anaemia in pigs (IAP), whereas M. parvum usually results in chronic and subclinical infections associated with performance losses. Little is known about the clinical significance of the recently discovered third porcine species 'Ca. M. haemosuis'. So far, the described pathogenic mechanisms mainly include direct destruction of erythrocytes via adhesion, invasion, eryptosis and nutrient scavenging, indirect erythrocyte lysis due to immune-mediated events and immune dysregulation processes. A review of published diagnostic data confirms PCR assays as the current standard method, with various cross-species and species-specific protocols. Overall, there is a need for further examination to obtain valuable insights for practical application, specifically regarding the importance of subclinical infections in naturally infected animals. An essential requirement for this will be to gain a more comprehensive understanding of the mechanisms operating between the host and the pathogen.

First molecular detection of Mycoplasma ovis (Hemotropic mycoplasmas) from Sheep in Brazil

Mycoplasma ovis is an emerging zoonotic pathogen with a worldwide distribution and can cause mild to severe hemolytic anemia, icterus, and poor weight gain in animals. Although M. ovis has been described in small ruminants worldwide, data on M. ovis in sheep in Brazil is unknown. The objective of the present study was to present the first report of hemotropic mycoplasma (HM) in sheep from Brazil. We evaluated factors associated with this infection, such age group, tick presence, and anemia. Blood samples were collected from 33 sheep from a farm in southern Brazil and screened for hemoplasmas using PCR. Out of 33 samples, 26 (78.8%) tested positive for M. ovis. The sequencing of positive samples showed 100% identity with multiple M. ovis 16S rDNA sequences. No association was observed between the presence of M. ovis and the FAMACHA© score (p = 0.620). Rhipicephalus (Boophilus) microplus (15/33, 45.4%) was the tick species found on the animals. No significant association between M. ovis infection and presence of ticks (p = 0.4134) and age group (p = 0.4221) was observed. This is the first report of M. ovis infection in sheep from Brazil and only the second report of this pathogen in sheep in Latin America.

First molecular detection of Mycoplasma suis in the pig louse Haematopinus suis (Phthiraptera: Anoplura) from Argentina

Porcine haemoplasmosis caused by Mycoplasma suis affects the global pig industry with significant economic losses. The main transmission route of M. suis is through the blood and some haematophagous arthropods, like flies and mosquitoes, could be the vectors to this pathogen. However, the presence of M. suis in pig haematophagous ectoparasites in natural conditions has not yet been studied. The most frequent ectoparasite in pigs is the blood-sucking louse Haematopinus suis, an obligate and permanent parasite. Therefore, this work aims to study the occurrence of M. suis in H. suis samples from both domestic and wild pig populations from Argentina; using the 16S rRNA gene. A total of 98 sucking lice, collected from domestic and wild pigs from Buenos Aires Province in central Argentina, were examined. We found M. suis DNA in 15 H. suis samples (15.30%). Positive lice were detected from all studied populations. This is the first report of M. suis presence in H. suis, being also the first detection in a pig ectoparasite species. We conclude that H. suis could serve as a mechanical vector for M. suis. This information not only extends the knowledge about the pathogen spectrum potentially transmitted by H. suis, but may be also useful in epidemiological studies about Mycoplasma.

Genome-wide identification and expression analysis of calcium-dependent protein kinase and its closely related kinase genes in Capsicum annuum

As Ca2+ sensors and effectors, calcium-dependent protein kinases (CDPKs) play important roles in plant growth, development, and response to environmental cues. However, no CDPKs have been characterized in Capsicum annuum thus far. Herein, a genome wide comprehensive analysis of genes encoding CDPKs and CDPK-related protein kinases (CRKs) was performed in pepper, a total of 31 CDPK genes and five closely related kinase genes were identified, which were phylogenetically divided into four distinct subfamilies and unevenly distributed across nine chromosomes. Conserved sequence and exon-intron structures were found to be shared by pepper CDPKs within the same subfamily, and the expansion of the CDPK family in pepper was found to be due to segmental duplication events. Five CDPKs in the C. annuum variety CM334 were found to be mutated in the Chiltepin variety, and one CDPK present in CM334 was lost in Chiltepin. The majority of CDPK and CRK genes were expressed in different pepper tissues and developmental stages, and 10, 12, and 8 CDPK genes were transcriptionally modified by salt, heat, and Ralstonia solanacearum stresses, respectively. Furthermore, these genes were found to respond specifically to one stress as well as respond synergistically to two stresses or three stresses, suggesting that these CDPK genes might be involved in the specific or synergistic response of pepper to salt, heat, and R. solanacearum. Our results lay the foundation for future functional characterization of pepper CDPK and its closely related gene families.

Microscopy and genomic analysis of Mycoplasma parvum strain Indiana

Mycoplasma parvum [Eperythrozoon parvum] is the second hemotrophic mycoplasma (hemoplasma) described in pigs. Unlike M. suis, its closest phylogenetic relative, M. parvum, is considered a non-pathogenic bacterium in this host species. Natural infection of a domestic, 6-month-old splenectomized pig with M. parvum strain Indiana is described herein. Light and scanning electron microscopy of the bacteria were performed in addition to whole genome sequencing, analysis, and comparison to the genome of M. suis strain Illinois. Neither clinical signs nor anemia were observed during the infection. Microscopy analyses revealed coccoid to rod- shaped organisms varying from 0.2 to 0.5 μm; they were observed individually or in short chains by both light and electron microscopy, however less than 30% of the red blood cells were infected at peak bacteremia. The single circular chromosome of M. parvum was only 564 395 bp, smaller than M. genitalium, previously considered the tiniest member of the Mollicutes. Its general genomic features were similar to others in this class and species circumscription was verified by phylogenomic analysis. A gene-by-gene comparison between M. suis and M. parvum revealed all protein coding sequences (CDS) with assigned functions were shared, including metabolic functions, transporters and putative virulence factors. However, the number of CDS in paralogous gene families was remarkably different with about half as many paralogs in M. parvum. The differences in paralogous genes may be implicated in the different pathogenic potential of these two species, however variable gene expression may also play a role. Both are areas of ongoing investigation.

Seroprevalence and risk factors of Mycoplasma suis infection in pig farms in central China

Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1-ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR=0.24; 95% CI: 0.07, 0.88; P=0.031) and frequency of disinfection (OR=0.23; 95% CI: 0.06, 0.90; P=0.035) were protective factors, and the presence of mosquitoes and flies (OR=5.994; 95% CI: 1.56, 23.00; P=0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.