Characterization of Prototheca zopfii associated with outbreak of bovine clinical mastitis in herd of Beijing, China

Investigation of Prototheca bovis Infection and Its Correlation with Dairy Herd Improvement Data from a Dairy Farm in Central China

Prototheca bovis (P. bovis), an alga that has attracted considerable attention over the years as a causative microorganism of mastitis in dairy cows, exhibits limited susceptibility to specific aminoglycosides and antifungal agents, and no effective clinical treatment is currently available, thereby posing challenges for both prevention and treatment. To investigate the infection of P. bovis mastitis and its impact on raw milk production, a total of 348 raw milk samples were collected from August to December 2022 from a dairy farm in central China. P. bovis and other bacteria were detected, and the average infection rate of P. bovis in raw milk was 60.34% (210/348). The total number of colonies and the somatic cell count (SCC) of P. bovis positive samples were significantly higher than those of P. bovis negative samples (p < 0.01). The daily milk yield, 305-day milk yield, peak milk yield, and days to peak milk yield of the P. bovis positive samples were significantly lower than those of P. bovis negative samples (p < 0.01). A correlation analysis showed that P. bovis infection was negatively correlated with daily milk yield, 305-day milk yield, peak milk yield, and days to peak milk yield (p < 0.0001), while being positively correlated with the total number of colonies, SCC, milk loss, and protein percentage (p < 0.0001). These findings may help practitioners in comprehending the occurrence of Prototheca mastitis and developing more effective strategies for the prevention of P. bovis infections.

Development of Loop-Mediated Isothermal Amplification for the Detection of Prototheca bovis Directly from Milk Samples of Dairy Cattle

Prototheca bovis is an algal emerging pathogen in dairy farms causing refractory protothecal mastitis with increasing incidence worldwide and significant economic impact. P. bovis infects cows throughout the lactation cycle, including dry periods, and can persist in the udder and the environment for a long time. Since P. bovis does not respond to treatments with antibiotics, the suggested sanitary measure to restrict the spread is culling infected animals. A point-of-care test for early detection of the causative agent is critically needed to guide farm management and the appropriate treatment of mastitis. Loop-mediated isothermal amplification (LAMP) is a highly specific molecular method, time-saving, cost-effective and easy to perform in limited settings. This study aimed to develop a LAMP assay for P. bovis detection directly from milk samples; it was employed in conjunction with a commercial DNA extraction kit which was previously used to extract DNA from milk specimens containing microbes. The LAMP assay detected P. bovis DNA within 1 h in milk samples spiked with P. bovis at a concentration of 50 cells/μL, enabling on-farm disease monitoring and decision-making based on a reliable diagnosis. The LAMP method will contribute to the accurate and rapid identification of P. bovis in asymptomatic or recurrent mastitis cases and consequently aid the implementation of targeted control measures and the reduction of losses in milk production.

Occurrence of Prototheca Microalgae in Aquatic Ecosystems with a Description of Three New Species, Prototheca fontanea, Prototheca lentecrescens, and Prototheca vistulensis

The study investigates the occurrence of very rare and poorly studied microalgae of the genus Prototheca , potentially pathogenic to humans and animals, in different water environments. Given the potential hazard to human and animal health from exposure to water-inhabiting protothecae, the prevalence of the algae in aquatic habitats deserves an insightful examination.

Prototheca spp. induce an inflammatory response via mtROS-mediated activation of NF-κB and NLRP3 inflammasome pathways in bovine mammary epithelial cell cultures

Emergence of bovine mastitis caused by Prototheca algae is the impetus to better understand these infections. Both P. bovis and P. ciferrii belong to Prototheca algae, but they differ in their pathogenicity to induce inflammatory responses. The objective was to characterize and compare pathogenesis of inflammatory responses in bMECs induced by P. bovis versus P. ciferrii. Mitochondrial ultrastructure, activity and mtROS in bMECs were assessed with transmission electron microscopy and laser scanning confocal microscopy. Cytokines, including TNF-α, IL-1β and IL-18, were measured by ELISA and real-time PCR, whereas expressions of various proteins in the NF-κB and NLRP3 inflammasome pathways were detected with immunofluorescence or Western blot. Infection with P. bovis or P. ciferrii damaged mitochondria, including dissolution and vacuolation of cristae, and decreased mitochondrial activity, with P. bovis being more pathogenic and causing greater destruction. There were increases in NADPH production and mtROS accumulation in infected bMECs, with P. bovis causing greater increases and also inducing higher cytokine concentrations. Expressions of NF-κB-p65, p-NF-κB-p65, IκBα and p-IκBα proteins in the NF-κB pathway, as well as NLRP3, Pro Caspase1, Caspase1 p20, ASC, Pro IL-1β, and IL-1β proteins in the NLRP3 inflammasome pathway, were significantly higher in P. bovis-infected bMECs. However, mito-TEMPO significantly inhibited production of cytokines and decreased expression of proteins in NF-κB and NLRP3 inflammasome pathways in bMECs infected with either P. bovis or P. ciferrii. In conclusion, P. bovis or P. ciferrii infections induced inflammatory responses in bMECs, with increased mtROS in damaged mitochondria and activated NF-κB and NLRP3 inflammasome pathways, with P. bovis causing a more severe reaction.

Susceptibility testing of Prototheca bovis isolates from cases of bovine mastitis using the CLSI reference broth microdilution method and the Sensititre YeastOne colorimetric panel

A total of 62 Prototheca bovis isolates from cases of bovine mastitis were tested for susceptibility to different antifungal compounds by the Clinical and Laboratory Standards Institute (CLSI) reference microdilution method and a commercial colorimetric microdilution panel (Sensititre YeastOne). All isolates displayed low susceptibility to echinocandins (MICs > 8 μg/ml for anidulafungin, caspofungin, and micafungin), flucytosine (MIC > 64 μg/ml), and the azoles enilconazole and fluconazole (MICs > 4 and > 64 μg/ml, respectively). Moreover, 45.2%, 32.3%, and 1.6% of isolates had MICs > 4 μg/ml for ketoconazole, terbinafine, and voriconazole, respectively, when tested by the CLSI method. In contrast, all isolates were more susceptible to the polyene compounds amphotericin B and nystatin, and itraconazole, posaconazole, and ravuconazole (MICs ≤ 2 μg/ml, in all cases). Comparison of the results obtained in the CLSI and Sensititre methods showed excellent essential agreement (EA) for azoles (98.4% for itraconazole and posaconazole, and 100% for voriconazole) and moderate EA for amphotericin B (72.6%), when MICs were read after 24 h and 48 h of incubation, respectively. In contrast, much lower EA values were obtained in some cases when the MICs for both techniques were determined after 48 h of incubation (e.g., 9.7% for amphotericin B and 69.4% for posaconazole). Therefore, the CLSI broth microdilution method and the Sensititre YeastOne panel can be used indistinctly for susceptibility testing of P. bovis isolates against azoles but not against amphotericin B until further optimization of the test conditions.

LAY SUMMARY

The antifungal susceptibility of Prototheca bovis isolates was analyzed. All tested isolates displayed low susceptibility to echinocandins, flucytosine, and some azoles. Excellent agreement of the results of two different test methods was obtained for azoles, but not for the polyene amphotericin B.

A survey of Prototheca bovis infection in dairy farms of the Hubei province, China

Bovine mastitis, caused by Prototheca bovis, has received much attention worldwide. To investigate the status of P. bovis infection in dairy farms of Hubei, we collected 1,158 milk samples and 90 environmental samples from 14 dairy farms of Hubei, China. The isolates were identified with traditional biological methods and molecular biological techniques, and their pathogenicity was tested through mice infection experiments. Isolates from 57 milk and 20 environmental samples were identified as P. bovis. The mice infection tests proved that the isolated P. bovis could cause mastitis in mice, manifesting as severe red swelling of the mammary glands. Histopathological analysis of tissue sections showed necrosis and nodules lesions formed in the infected mice mammary tissue, accompanied by macrophage and neutrophil infiltration. These results suggested the existence of pathogenic P. bovis in dairy farms of the Hubei province, China, with brewer's grains and fresh feces possibly playing important roles in the spread of this disease.

Preliminary Results, Perspectives, and Proposal for a Screening Method of In Vitro Susceptibility of Prototheca Species to Antimicrotubular Agents

Microorganisms belonging to the genus Prototheca are achlorophyllous microalgae, occasionally behaving as environmental pathogens that cause severe mastitis in milk cows, as well as localized or systemic infections in humans and animals. Among the different species belonging to the genus, Prototheca zopfii genotype 2 (recently reclassified as P. bovis) and P. blaschkeae are most commonly associated with bovine mastitis. To date, no pharmacological treatment is available to cure protothecal mastitis, and infected animals must be quarantined to avoid spreading the infection. The few antibiotic and antifungal drugs effective in vitro against Prototheca give poor results in vivo This failure is likely due to the lack of specificity of such drugs. As microalgae are more closely related to plants than to bacteria or fungi, an alternative possibility is to test molecules with herbicidal properties, in particular, antimicrotubular herbicides, for which plant rather than animal tubulin is the selective target. Once a suitable test protocol was set up, a panel of 11 antimicrotubular agents belonging to different chemical classes and selective for plant tubulin were tested for the ability to inhibit growth of Prototheca cells in vitro Two dinitroanilines, dinitramine and chloralin, showed strong inhibitory effects on P. blaschkeae at low micromolar concentrations, with half-maximal inhibitory concentrations (IC₅₀) of 4.5 and 3 μM, respectively, while both P. zopfii genotype 1 (now reclassified as P. ciferrii) and P. bovis showed susceptibility to dinitramine only, to different degrees. Suitable screening protocols for antimitotic agents are suggested.

Murine and Human Cathelicidins Contribute Differently to Hallmarks of Mastitis Induced by Pathogenic Prototheca bovis Algae

Prototheca bovis (formerly P. zopfii genotype-II) is an opportunistic, achlorophyllous alga that causes mastitis in cows and skin disease in cats and dogs, as well as cutaneous lesions in both immunocompetent and immunosuppressed humans. Antifungal medications are commonly ineffective. This study aimed to investigate innate immune responses contributed by cathelicidins to P. bovis in the mammary gland using a mastitis model in mice deficient in the sole murine cathelicidin (Camp). We determined P. bovis caused acute mastitis in mice and induced Camp gene transcription. Whereas, Camp ^-/- and Camp ^+/+ littermates had similar local algae burden, Camp ^+/+ mice produced more pro-inflammatory cytokines, TNF-α, and Cxcl-1. Likewise, Camp ^+/+ bone marrow-derived macrophages were more responsive to P. bovis, producing more TNF-α and Cxcl-1. Human cathelicidin (LL-37) exhibited a different effect against P. bovis; it had direct algicidal activity against P. bovis and lowered TNF-α, Cxcl-1, and IL-1β production in both cultured murine macrophages and mammary epithelial cells exposed to the pathogenic algae. In conclusion, cathelicidins were involved in protothecosis pathogenesis, with unique roles among the diverse peptide family. Whereas, endogenous cathelicidin (Camp) was key in mammary gland innate defense against P. bovis, human LL-37 had algicidal and immunomodulatory functions.

Prototheca zopfii genotype II induces mitochondrial apoptosis in models of bovine mastitis

Prototheca zopfii is an alga increasingly isolated from bovine mastitis. Of the two genotypes of P. zopfii (genotype I and II (GT-I and -II)), P. zopfii GT-II is the genotype associated with acute mastitis and decreased milk production, although its pathogenesis is not well known. The objective was to determine inflammatory and apoptotic roles of P. zopfii GT-II in cultured mammary epithelial cells (from cattle and mice) and murine macrophages and using a murine model of mastitis. Prototheca zopfii GT-II (but not GT-I) invaded bovine and murine mammary epithelial cells (MECs) and induced apoptosis, as determined by the terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling assay. This P. zopfii GT-II driven apoptosis corresponded to mitochondrial pathways; mitochondrial transmembrane resistance (ΔΨm) was altered and modulation of mitochondrion-mediated apoptosis regulating genes changed (increased transcriptional Bax, cytochrome-c and Apaf-1 and downregulated Bcl-2), whereas caspase-9 and -3 expression increased. Apoptotic effects by P. zopfii GT-II were more pronounced in macrophages compared to MECs. In a murine mammary infection model, P. zopfii GT-II replicated in the mammary gland and caused severe inflammation with infiltration of macrophages and neutrophils and upregulation of pro-inflammatory genes (TNF-α, IL-1β and Cxcl-1) and also apoptosis of epithelial cells. Thus, we concluded P. zopfii GT-II is a mastitis-causing pathogen that triggers severe inflammation and also mitochondrial apoptosis.

Prevalence of Prototheca spp. on dairy farms in Poland - a cross-country study

The Prototheca algae have recently emerged as an important cause of bovine mastitis globally. Here, we present results of a first large-scale, cross-country survey on the prevalence of Prototheca spp. in dairy cows, and their environment in Poland. A total of 1211 samples were collected and microbiologically analysed. Included within this number were milk (n = 638), body swabs (n = 374) and environmental samples (n = 199), originating from 400 dairy cows and their surroundings, on 16 dairy farms, based in all major provinces of the country. Prototheca spp. were the third, after Streptococcus and Staphylococcus spp., most common mastitis pathogens. The overall prevalence of protothecal mastitis was 8.3% (33/400), with the majority (75.8%) of cases having a subclinical course, and all but one attributable to P. zopfii genotype 2. Prototheca spp. were cultured from body swabs of both healthy and mastitic cows, yet the isolation rate among the latter was conspicuously lower (12.3% vs. 17.8%). Forty-two (21.2%) environmental samples yielded growth of Prototheca spp. However, no clear association between Prototheca mastitis in dairy cows and the algal isolation from the herd environment was found. Nor was there any association between the environmental recovery of the algae and farm management practices.

Genome sequencing of Prototheca zopfii genotypes 1 and 2 provides evidence of a severe reduction in organellar genomes

Prototheca zopfii (P. zopfii, class Trebouxiophyceae, order Chlorellales, family Chlorellaceae), a non-photosynthetic predominantly free-living unicellular alga, is one of the few pathogens belonging to the plant kingdom. This alga can affect many vertebrate hosts, sustaining systemic infections and diseases such as mastitis in cows. The aim of our work was to sequence and assemble the P. zopfii genotype 1 and genotype 2 mitochondrial and plastid genomes. Remarkably, the P. zopfii mitochondrial (38 Kb) and plastid (28 Kb) genomes are models of compaction and the smallest known in the Trebouxiophyceae. As expected, the P. zopfii genotype 1 and 2 plastid genomes lack all the genes involved in photosynthesis, but, surprisingly, they also lack those coding for RNA polymerases. Our results showed that plastid genes are actively transcribed in P. zopfii, which suggests that the missing RNA polymerases are substituted by nuclear-encoded paralogs. The simplified architecture and highly-reduced gene complement of the P. zopfii mitochondrial and plastid genomes are closer to those of P. stagnora and the achlorophyllous obligate parasite Helicosporidium than to those of P. wickerhamii or P. cutis. This similarity is also supported by maximum likelihood phylogenetic analyses inferences. Overall, the P. zopfii sequences reported here, which include nuclear genome drafts for both genotypes, will help provide both a deeper understanding of the evolution of Prototheca spp. and insights into the corresponding host/pathogen interactions.

cytb as a New Genetic Marker for Differentiation of Prototheca Species

Achlorophyllous unicellular microalgae of the genus Prototheca (Trebouxiophyceae, Chlorophyta) are the only known plants that cause infections in both humans and animals, collectively referred to as protothecosis. Human protothecosis, most commonly manifested as cutaneous, articular, and disseminated disease, is primarily caused by Protothecawickerhamii, followed by Protothecazopfii and, sporadically, by Protothecacutis and Protothecamiyajii In veterinary medicine, however, P. zopfii is a major pathogen responsible for bovine mastitis, which is a predominant form of protothecal disease in animals. Historically, identification of Prototheca spp. has relied upon phenotypic criteria; these were later replaced by molecular typing schemes, including DNA sequencing. However, the molecular markers interrogated so far, mostly located in the ribosomal DNA (rDNA) cluster, do not provide sufficient discriminatory power to distinguish among all Prototheca spp. currently recognized. Our study is the first attempt to develop a fast, reliable, and specific molecular method allowing identification of all Prototheca spp. We propose the mitochondrial cytb gene as a new and robust marker for diagnostics and phylogenetic studies of the Prototheca algae. The cytb gene displayed important advantages over the rDNA markers. Not only did the cytb gene have the highest discriminatory capacity for resolving all Prototheca species, but it also performed best in terms of technical feasibility, understood as ease of amplification, sequencing, and multiple alignment analysis. Based on the species-specific polymorphisms in the partial cytb gene, we developed a fast and straightforward PCR-restriction fragment length polymorphism (RFLP) assay for identification and differentiation of all Prototheca species described so far. The newly proposed method is advocated to be a new gold standard in diagnostics of protothecal infections in human and animal populations.

The activity of silver nanoparticles against microalgae of the Prototheca genus

AIM

To investigate the in vitro activity of silver NPs (AgNPs) against pathogenic microalgae of the Prototheca genus.

MATERIALS & METHODS

The antialgal potential of AgNPs against Prototheca species of both clinical and environmental origin was assessed from minimum inhibitory (algistatic) and algicidal concentrations. The in vitro cytotoxicity of AgNPs against bovine mammary epithelial cell line was evaluated by means of the standard MTT assay.

RESULTS

AgNPs showed a strong killing activity toward Prototheca algae, as the minimal algicidal concentration (MAC) values matched perfectly the corresponding minimum inhibitory concentration (MIC) values for all species (MAC = MIC, 1-4 mg/l), except P. stagnora (MIC > 8 mg/l). The concentrations inhibitory to pathogenic Prototheca spp. (MIC, 1-4 mg/l) were below the concentrations at which any toxicity in epithelial cells could be observed (CC₂₀ > 6 mg/l).

CONCLUSION

The study emphasizes the potential of AgNPs as a new therapeutic tool for the management of Prototheca infections.

The in vitro efficacy of SunSmile® Fruit & Vegetable Rinse against pathogenic strains of Prototheca algae that cause mastitis in cows

The research concerns algae of the genus Prototheca. They are found in the natural environment and they can cause a disease in animals and humans called protothecosis. The aim of the study was to evaluate the in vitro activity of the fruit and vegetable rinse agent SunSmile^® Fruit & Vegetable Rinse (Sunrider International) against P. zopfii isolates. The materials consisted of ten P. zopfii strains isolated from the milk of cows with mastitis. The following antifungal chemotherapeutic agents were also used in the study for comparison: nystatin, ketoconazole, amphothericin B, miconazole, clotrimazole, econazole, fluconazole, and flucytosine. The tube dilution method were used to evaluate the effect of a fruit and vegetable rinse agent and the disc-diffusion method to evaluate the effect of antifungal chemotherapeutic agents on P. zopfii strains. All tested strains of P. zopfii were susceptible to the action of the SunSmile^® agent. The MMC was in the range of 0.0024-0.0190%. The SunSmile^® Fruit & Vegetable Rinse can be used in prevention of mastitis in cows and in human protothecosis due to its safe, natural composition and efficacy.

3-Bromopyruvate as an Alternative Option for the Treatment of Protothecosis

Protothecosis is an unusual infection of both humans and animals caused by opportunistically pathogenic microalgae of the genus Prototheca. Until now, no standardized treatment protocols exist for the protothecal disease, boosted by a remarkable resistance of Prototheca spp. to a wide array of antimicrobial agents currently available in clinical use. Consequently, there is an urgent need for new effective drugs against Prototheca algae. In this study, the anti-Prototheca activity of 3-bromopyruvate (3BP), either alone or in combination with amphotericin B (AMB) was assessed in vitro, as well as the cytotoxicity of 3BP toward the bovine mammary epithelial cells and murine skin fibroblasts. The mean minimum inhibitory concentrations (MIC) and minimum algaecidal concentrations (MAC) were 0.85 ± 0.21 and 2.25 ± 0.54 mM for Prototheca wickerhamii, 1.25 ± 0.47 and 4.8 ± 1.03 mM for Prototheca blaschkeae, and 1.55 ± 0.69 and 5.6 ± 1.3 mM for Prototheca zopfii gen. 2, respectively. For all Prototheca strains tested, a synergistic interaction between 3BP and AMB was observed, resulting in about 4-fold reduction of their individual MICs, when used together. The elevated content of intracellular glutathione (GSH) was associated with a decreased susceptibility to 3BP. Both epithelial and fibroblast cells retained high viability upon treatment with 3BP at concentrations equivalent to the highest MIC recorded (3 mM) and 10-fold higher (30 mM), with the mean cell viability exceeding 80%, essentially the same as for the untreated cells. The results from these in vitro studies emphasize the high activity of 3BP against the Prototheca algae, its synergistic effect when used in combination with AMB, and the safety of the drug toward the tested mammalian cells. Along with the advantageous physico-chemical and pharmacokinetic properties, 3BP may be considered an effective and safe novel agent against the protothecal disease.

Prototheca zopfii isolated from bovine mastitis induced oxidative stress and apoptosis in bovine mammary epithelial cells

Bovine protothecal mastitis results in considerable economic losses worldwide. However, Prototheca zopfii induced morphological alterations and oxidative stress in bovine mammary epithelial cells (bMECs) is not comprehensively studied yet. Therefore, the aim of this current study was to investigate the P. zopfii induced pathomorphological changes, oxidative stress and apoptosis in bMECs. Oxidative stress was assessed by evaluating catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA) contents and lactate dehydrogenase (LDH) activity, while ROS generation and apoptosis was measured by confocal laser scanning microscopy. The results revealed that infection of P. zopfii genotype II (GTII) significantly changed bMECs morphology, increased apoptotic rate and MDA contents at 12 h (p < 0.05) and 24 h (p < 0.01) in comparison with control group, in time-dependent manner. LDH activity and ROS generation was also increased (p < 0.01) at 12 h and 24 h. However, SOD and CAT contents in bMECs infected with GTII were decreased (p < 0.05) at 12 h, while GPx (p < 0.01), SOD (p < 0.05) and CAT (p < 0.01) levels were reduced at 24 h. In case of GTI, only CAT and GPx activities were significantly decreased when the duration prolonged to 24 h but lesser than GTII. This suggested that GTII has more devastating pathogenic effects in bMECs, and the findings of this study concluded that GTII induced apoptosis and oxidative stress in bMECs via the imbalance of oxidant and antioxidant defenses as well as the production of intracellular ROS.

Prototheca zopfii Induced Ultrastructural Features Associated with Apoptosis in Bovine Mammary Epithelial Cells

Prototheca zopfii infections are becoming global concerns in humans and animals. Bovine protothecal mastitis is characterized by deteriorating milk quality and quantity, thus imparting huge economic losses to dairy industry. Previous published studies mostly focused on the prevalence and characterization of P. zopfii from mastitis. However, the ultrastructural pathomorphological changes associated with apoptosis in bovine mammary epithelial cells (bMECs) are not studied yet. Therefore, in this study we aimed to evaluate the in vitro comparative apoptotic potential of P. zopfii genotype-I and -II on bMECs using flow cytometry, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed fast growth rate and higher adhesion capability of genotype-II in bMECs as compared with genotype-I. The viability of bMECs infected with P. zopfii genotype-II was significantly decreased after 12 h (p < 0.05) and 24 h (p < 0.01) in comparison with control cells. Contrary, genotype-I couldn't show any significant effects on cell viability. Moreover, after infection of bMECs with genotype-II, the apoptosis increased significantly at 12 h (p < 0.05) and 24 h (p < 0.01) as compared with control group. Genotype-I couldn't display any significant effects on cell apoptosis. The host specificity of P. zopfii was also tested in mouse osteoblast cells, and the results suggest that genotype-I and -II could not cause any significant apoptosis in these cell lines. SEM interpreted the pathomorphological alterations in bMECs after infection. Adhesion of P. zopfii with cells and further disruption of cytomembrane validated the apoptosis caused by genotype-II under SEM. While genotype-1 couldn't cause any significant apoptosis in bMECs. Furthermore, genotype-II induced apoptotic manifested specific ultrastructure features, like cytoplasmic cavitation, swollen mitochondria, pyknosis, cytomembrane disruption, and appearance of apoptotic bodies under TEM. The findings of the current study revealed that genotype-II has the capability to invade and survive within the bMECs, thus imparting significant damages to the mammary cells which result in apoptosis. This study represents the first insights into the pathomorphological and ultrastructure features of apoptosis in bMECs induced by P. zopfii genotype-II.

Whole-genome regulation analysis of histone H3 lysin 27 trimethylation in subclinical mastitis cows infected by Staphylococcus aureus

Background

S. aureus is one of the major etiological agents causing bovine subclinical mastitis. The regulatory effects of H3K27me3 on gene expression in subclinical S. aureus mastitis cows are unknown. This study aimed to profile genome-wide transcriptional changes regulated by H3K27me3 in bovine lymphocytes applied in subclinical S. aureus mastitis cows and healthy controls.

Results

A total of 61 differentially expressed genes (DEGs) were detected in subclinical S. aureus mastitis cows compared to the healthy controls, of which 25 DEGs are up-regulated and the rest are down-regulated genes in subclinical S.aureus mastitis cows. The up-regulated genes are mainly involved in the Jak-STAT signaling pathway, cytokine-cytokine receptor interaction, and T cell receptor-signaling pathway, while the down-regulated genes are related to metabolism pathways. Combination analysis of histone methylation and gene expression revealed that H3K27 trimethylation levels in silent genes were higher in subclinical S. aureus mastitis cattle than in healthy cows. The key regions of H3K27me3 target genes related to subclinical S. aureus mastitis were the upstream 2 kb regions of the DEGs relative to transcription start site (TSS).

Conclusions

The current study provides a novel insight into the interaction between S. aureus and lymphocytes in lactating cows by histone H3 methylation regulation. The differentially expressed genes in bovine lymphocytes regulated by H3K27me3 on upstream 2 kb regions (IL10, PTX3 and etc.) may relate to S. aureus mastitis susceptibility and could be considered as key candidate genes for anti- S. aureus mastitis study and breeding.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2947-0) contains supplementary material, which is available to authorized users.

Combined analysis of DNA methylome and transcriptome reveal novel candidate genes with susceptibility to bovine Staphylococcus aureus subclinical mastitis

Subclinical mastitis is a widely spread disease of lactating cows. Its major pathogen is Staphylococcus aureus (S. aureus). In this study, we performed genome-wide integrative analysis of DNA methylation and transcriptional expression to identify candidate genes and pathways relevant to bovine S. aureus subclinical mastitis. The genome-scale DNA methylation profiles of peripheral blood lymphocytes in cows with S. aureus subclinical mastitis (SA group) and healthy controls (CK) were generated by methylated DNA immunoprecipitation combined with microarrays. We identified 1078 differentially methylated genes in SA cows compared with the controls. By integrating DNA methylation and transcriptome data, 58 differentially methylated genes were shared with differently expressed genes, in which 20.7% distinctly hypermethylated genes showed down-regulated expression in SA versus CK, whereas 14.3% dramatically hypomethylated genes showed up-regulated expression. Integrated pathway analysis suggested that these genes were related to inflammation, ErbB signalling pathway and mismatch repair. Further functional analysis revealed that three genes, NRG1, MST1 and NAT9, were strongly correlated with the progression of S. aureus subclinical mastitis and could be used as powerful biomarkers for the improvement of bovine mastitis resistance. Our studies lay the groundwork for epigenetic modification and mechanistic studies on susceptibility of bovine mastitis.

Molecular typing and differences in biofilm formation and antibiotic susceptibilities among Prototheca strains isolated in Italy and Brazil

Bovine mastitis caused by Prototheca is a serious and complex problem that accounts for high economic losses in the dairy industry. The main objective of this study was to identify and characterize at genetic level different Prototheca strains and provide the most complete data about protothecal antibiotic resistance. The study involves 46 isolates from Italian (13 strains) and Brazilian (33 strains) mastitic milk. These strains were identified by multiplex PCR and single strand conformation polymorphism analysis and characterized by randomly amplified polymorphic DNA (RAPD)-PCR. Moreover, biofilm production and antibiotic susceptibility were evaluated. Forty-two strains resulted as Prototheca zopfii genotype 2, whereas 4 isolates could belong to a potential new Prototheca species. The RAPD-PCR, performed with 3 primers (M13, OPA-4, and OPA-18), showed a notable heterogeneity among isolates and grouped the strains according to the species and geographical origin. Biofilm production was species-dependent and P. zopfii genotype 2 strains were classified as strong biofilm producers. In vitro antibiotic susceptibility tests indicated that Prototheca strains were susceptible to antibacterial drugs belonging to aminoglycosides group; the highest activity against Prototheca strains was observed in the case of colistin sulfate, gentamicin, and netilmicin (100% of susceptible strains). It is interesting to note that all the Italian P. zopfii genotype 2 strains showed lower minimum inhibitory concentration values than the Brazilian ones. Nisin showed more efficacy than lysozyme and potassium sorbate, inhibiting 31% of the strains. Results obtained in this study confirmed that RAPD-PCR is a rapid, inexpensive, and highly discriminating tool for Prototheca strains characterization and could give a good scientific contribution for better understanding the protothecal mastitis in dairy herd.

Characterization of Prototheca zopfii Genotypes Isolated from Cases of Bovine Mastitis and Cow Barns in China

Protothecal mastitis, caused mostly by Prototheca zopfii (P. zopfii), is increasing in dairy herds and is being reported globally. The present study was aimed at studying the epidemiology of mastitis and at molecular characterization of P. zopfii isolates from dairy herds and their surroundings in three provinces of China using microbiological, biochemical and molecular methods, and antibiotic susceptibility tests. Samples from milk (n = 620) of mastitic cows and their barns sources (n = 410) including feces, feed, bedding materials and drinking water were analyzed. Among other pathogens recovered from mastitic milk, 84 (13.5%) of the isolates were identified as P. zopfii. All of the P. zopfii isolates recovered from milk were recognized as genotype 2, whereas 58 (73.4%) and 21 (26.6%) isolates from environmental sources were found to be P. zopfii genotypes 1 and 2, respectively. The isolates were susceptible to some antibiotics and antifungal agents, including amikacin (78.1%), streptomycin (58.5%), gentamicin (17.8%), amphotericin B (68.6%) and nystatin (64.4%). Additionally, the two genotypes displayed versatile patterns of susceptibility to different antimicrobials agents. Phylogeny of the genotypes on the basis of 18S SSU rDNA and 28S SSU rDNA was also investigated. The isolates of the two genotypes separated into different clades, and no interrelationship was observed among these as shown by phylogenetic analysis. The genotype 1 isolates from cow barn sources were non-pathogenic and may not present any risk of mastitis. We conclude that P. zopfii genotype 2 might play an important role in bovine mastitis in China.

Internal transcribed spacer sequence-based rapid molecular identification of Prototheca zopfii and Prototheca blaschkeae directly from milk of infected cows

The increasing incidence of rare mastitis-causing pathogens has urged the implementation of fast and efficient diagnostic and control measures. Prototheca algae are known to be associated with diseases in humans and animals. In the latter, the most prevalent form of protothecosis is bovine mastitis with Prototheca zopfii and Prototheca blaschkeae representing the most common pathogenic species. These nonphotosynthetic and colorless green algae are ubiquitous in different environments and are widely resistant against harmful conditions and antimicrobials. Hence, the association of Prototheca with bovine mastitis represents a herd problem, requiring fast and easy identification of the infectious agent. The purpose of this study was to develop a reliable and rapid method, based on the internal transcribed spacer (ITS) sequences of ribosomal DNA, for molecular identification and discrimination between P. zopfii and P. blaschkeae in bovine mastitic milk. The complete ITS sequences of 32 Prototheca isolates showed substantial interspecies but moderate intraspecies variability facilitating the design of species-specific PCR amplification primers. The species-specific PCR was successfully applied to the identification of P. zopfii and P. blaschkeae directly from milk samples. The intraspecific ITS phylogeny was compared for each species with the geographical distribution of the respective Prototheca isolates, but no significant correlation was found.

Canine ocular protothecosis: A review of 14 cases

PURPOSE

To examine a series of 14 cases of canine ocular protothecosis from archived cases from the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW), and compare gross and histologic findings.

METHODS

Archival records from COPLOW were searched for canine cases of ocular protothecosis. Fourteen cases that contained matching criteria were identified, and gross and histologic findings, and clinical records for each case were tabulated, examined, and compared (2001-2013).

RESULTS

Of the 14 cases identified, six had evidence of systemic disease, as per clinical history. Two of the 14 cases had Prototheca identified via cytology of ocular fluid or retinal exudate; in the remainder of cases, Prototheca identified via cytology of ocular fluid or retinal exudate in the remaining 12 cases, Prototheca was identified upon histologic examination of the submitted globe(s). Presenting ocular clinical signs were variable and nonspecific. Duration of ocular clinical signs varied from days to months. Fundoscopically, white membranes or plaques were identified on or around the retina in five cases. Retinal detachment was identified in 13 of the 14 submitted globes on gross examination following fixation and sectioning. The predominant histologic finding was granulomatous chorioretinitis with retinal detachment, with variable numbers of Prototheca within the inflammatory infiltrate.

CONCLUSIONS

Due to the nonspecific nature of the ocular signs, a diagnosis of protothecosis generally is not made until enucleation and histopathologic examination of the globe(s). Retinal detachment and blindness were common. Cytologic sampling of retinal plaques and exudate may provide a rapid way to identify Prototheca.

Simultaneous identification by multiplex PCR of major Prototheca spp. isolated from bovine and buffalo intramammary infection and bulk tank

Bovine mastitis caused by Prototheca spp. infection is increasing worldwide, therefore becoming more relevant to the dairy industry. Almost all Prototheca isolates from bovine mammary protothecosis came from P. zopfii genotype 2, with a lower prevalence of infection due to P. blaschkeae and rarely to P. wickerhamii. In this study, we report the development of two multiplex PCR assays able to discriminate among the three species responsible for bovine intramammary infection (IMI). Our assay is based on the specific amplification of new DNA target from mitochondria and chloroplasts partial sequences, of different Prototheca isolates. Both methods were set up using reference strains belonging to all Prototheca species and validated by the analysis of 93 isolates from bovine and buffalo IMI and bulk tank milk samples. The investigation involves 70 isolates from North, 13 from Central and 10 from South Italian regions. Isolates from bovine were most commonly identified as P. zopfii genotype 2, and only in one case as P. blaschkeae, whereas isolates from buffaloes belonged both to P. zopfii genotype 2 and P. wickerhamii. These findings proved the suitability of our multiplex PCRs as a rapid test to discriminate among pathogenic Prototheca strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work reports PCR assays based on novel Prototheca spp. mitochondrial and chloroplastic target sequences. The multiplex PCR protocol described in this study is useful for rapid simultaneous detection of P. zopfii, P. wickerhamii and P. blaschkeae.

Antimicrobial activity of Mentha piperita and Saturenja hortensis in a murine model of cutaneous protothecosis

BACKGROUND

To date there is no defined pharmacologic treatment protocol available against cutaneous protothecosis, which is difficult to combat using conventional drugs.

OBJECTIVES

Our experiment aimed to comparatively investigate the effect of two essential oils (Mentha piperita and Saturenja hortensis) against cutaneous protothecosis experimentally induced by Prototheca zopfii in mice.

MATERIALS AND METHODS

Immunosuppressed BALB/c female mice, were divided into six experimental groups, infected with P. zopfii, and then treated for 21 days against the infection. The effectiveness of the different treatments was assessed clinically and histologically by quantifying the degree of inflammation (immunohistochemical quantification of macrophages, T lymphocytes and neutrophils) and fibrosis.

RESULTS

Skin lesions in experimental protothecosis from non-treated mice were more severe as compared to the four groups of treated animals. Both M. piperita and S. hortensis have proved to be efficient in vivo in the treatment of cutaneous protothecosis by reducing the clinical signs and significantly reducing the degree of inflammation (P<0.05 for the number of macrophages, T lymphocytes and neutrophils) and fibrosis as compared to untreated animals.

CONCLUSION

Interestingly, our study shows that M. piperita and S. hortensis could represent a potential source of natural antimicrobial products in the treatment of cutaneous protothecosis.

Treatment with gentamicin on a murine model of protothecal mastitis

The aim of this study was to establish a murine protothecal mastitis model and to evaluate the treatment efficiency of gentamicin. Challenge routes were determined with a pathogenic Prototheca zopfii genotype 2 (P. zopfii) strain. 25 BALB/c mice were inoculated in mammary glands with graded dosages (10(3), 10(4), 10(5), 10(6), 10(7) CFU of P. zopfii) and killed on the 7th day. Another 25 animals were also killed at 1, 3, 5, 7, and 9 days after inoculation of 1 × 10(6) CFU of P. zopfii, the milk somatic cell counts, pathological section of mammary glands, and P. zopfii burden were observed. The antimicrobial activity was tested using disc diffusion test and minimum inhibitory concentrations. Gentamicin was given intramuscularly to analyze the therapeutic effect. The results showed that the best infection route was intra-mammary gland, and the mastitis model was established with 1 × 10(6) CFU of P. zopfii. After infection, the somatic cell counts increased significantly. The pathological reaction mainly consisted of infiltration of inflammatory cells, destruction of acini, accumulation of lymphocyte cells and the severity of the changes was dosage and time-dependent. The P. zopfii burden revealed that P. zopfii continuously replicated. In vitro susceptibility tests indicated that the Prototheca strains were antimicrobial susceptible to gentamicin at concentrations between 0.03 and 4 μg/ml. In vivo therapeutic assay demonstrated that high concentrations of gentamicin (≥20 mg/kg) could inhibit the growth of P. zopfii. We conclude that the murine model of protothecal mastitis was established successfully and gentamicin may be an effective choice for treatment of P. zopfii.