The Arcanobacterium pyogenes collagen-binding protein, CbpA, promotes adhesion to host cells

Molecular Characterization of Resistance and Virulence Factors of Trueperella pyogenes Isolated from Clinical Bovine Mastitis Cases in China

Purpose

The present study was designed to investigate the resistance determinants and virulence factors of 45 Trueperella pyogenes isolates from clinical bovine mastitis in Hexi Corridor of Gansu, China.

Methods

Minimum inhibitory concentrations (MICs) was tested by E-test method. Gene of antimicrobial resistance, virulence integrase and integron gene cassettes were determined by PCR and DNA sequencing.

Results

The T. pyogenes isolates exhibited high resistance to streptomycin (88.9%) and tetracycline (64.4%), followed by erythromycin (15.6%) and gentamicin (13.3%). Resistance to streptomycin was most commonly encoded by aadA9 (88.9%); and to tetracycline, by tetW (64.4%). Importantly, all streptomycin-resistant isolates carried aadA9 alone or in combination with aadA1, aadA11 and strA-strB. Similarly, all tetracycline-resistant isolates harbored tetW alone or in combination with tetA33. Meanwhile, ermX was detected in 13.3% isolates, only one erythromycin-resistant isolate was not identified for this gene. Moreover, all T. pyogenes isolates carried class 1 integrons, and 17.8% of them contained gene cassettes, including arrays aadA1-aadB (4.4%), aad A24-dfrA1-ORF1 (2.2%) and aadA1 (2.2%). Furthermore, all tested isolates harbored virulent genes plo and fimA, followed by fimC (88.9%), fimE (86.6%) nanP (75.6%), nanH (40.0%), cbpA (35.6%) and fimG (6.7%).

Conclusion

To our knowledge, this is the first report of integron gene cassettes of T. pyogenes isolates from bovine mastitis cases in China. These findings are useful for developing the prevention and the virulence factors of T. pyogenes could be promising candidates for vaccine antigens for bovine mastitis caused by T. pyogenes in China.

Immunoinformatics design of novel multi-epitope vaccine against Trueperella Pyogenes using collagen adhesion protein, fimbriae, and pyolysin

Trueperella pyogenes (T. pyogenes) is an opportunistic pathogen that causes infertility, mastitis, and metritis in animals. T. pyogenes is also a zoonotic disease and is considered an economic loss agent in the livestock industry. Therefore, vaccine development is necessary. Using an immunoinformatics approach, this study aimed to construct a multi-epitope vaccine against T. pyogenes. The collagen adhesion protein, fimbriae, and pyolysin (PLO) sequences were initially retrieved. The HTL, CTL, and B cell epitopes were predicted. The vaccine was designed by binding these epitopes with linkers. To increase vaccine immunogenicity, profilin was added to the N-terminal of the vaccine construct. The antigenic features and safety of the vaccine model were investigated. Docking, molecular dynamics simulation of the vaccine with immune receptors, and immunological simulation were used to evaluate the vaccine's efficacy. The vaccine's sequence was then optimized for cloning. The vaccine construct was designed based on 18 epitopes of T. pyogenes. The computational tools validated the vaccine as non-allergenic, non-toxic, hydrophilic, and stable at different temperatures with acceptable antigenic features. The vaccine model had good affinity and stability to bovine TLR2, 4, and 5 as well as stimulation of IgM, IgG, IL-2, IFN-γ, and Th1 responses. This vaccine also increased long-lived memory cells, dendritic cells, and macrophage population. In addition, codon optimization was done and cloned in the E. coli K12 expression vector (pET-28a). For the first time, this study introduced a novel multi-epitope vaccine candidate based on collagen adhesion protein, fimbriae, and PLO of T. pyogenes. It is expected this vaccine stimulates an effective immune response to prevent T. pyogenes infection.

Research progress of nanoparticle targeting delivery systems in bacterial infections

Bacterial infection is a huge threat to the health of human beings and animals. The abuse of antibiotics have led to the occurrence of bacterial multidrug resistance, which have become a difficult problem in the treatment of clinical infections. Given the outstanding advantages of nanodrug delivery systems in cancer treatment, many scholars have begun to pay attention to their application in bacterial infections. However, due to the similarity of the microenvironment between bacterial infection lesions and cancer sites, the targeting and accuracy of traditional microenvironment-responsive nanocarriers are questionable. Therefore, finding new specific targets has become a new development direction of nanocarriers in bacterial prevention and treatment. This article reviews the infectious microenvironment induced by bacteria and a series of virulence factors of common pathogenic bacteria and their physiological functions, which may be used as potential targets to improve the targeting accuracy of nanocarriers in lesions.

Differences in phenotypic and genetic characteristics of Trueperella pyogenes detected in slaughtered cattle and pigs with septicemia

We investigated the hemolytic properties, biochemical properties, and possession of virulence factor genes of Trueperella pyogenes isolated from cattle and pigs with septicemia. The porcine strains showed significantly stronger hemolyticity than the bovine strains. In addition, T. pyogenes from cattle and pigs also differed in biochemical properties. Virulence factor genes (nanP, cbpA, fimC, and fimE) were more prevalent in bovine strains, whereas other virulence factor genes (nanH and fimG) were more prevalent in porcine strains. T. pyogenes isolated from pig and cattle with septis cases in Japanese meat inspection showed variability in biochemical and genetic properties. Differences were observed between porcine and bovine strain in term of the hemolytic strength and possession of genes for factors promoting adhesions which are considered pathogenic.

Phenotypic and molecular characterization of antimicrobial resistance in Trueperella pyogenes strains isolated from bovine mastitis and metritis

Background

Trueperella pyogenes is one of the most clinically imperative bacteria responsible for severe cases of mastitis and metritis, particularly in postpartum dairy cows. The bacterium has emergence of antibiotic resistance and virulence characters. The existing research was done to apprise the phenotypic and genotypic evaluation of antibiotic resistance and characterization of virulence factors in the T. pyogenes bacteria of bovine mastitis and metritis in postpartum cows.

Methods

Two-hundred and twenty-six bovine mastitic milk and 172 uterine swabs were collected and transferred to laboratory. Samples were cultured and T. pyogenes isolates were subjected to disk diffusion and DNA extraction. Distribution of virulence and antibiotic resistance genes was studied by PCR.

Results

Thirty-two out of 226 (14.15%) mastitic milk and forty-one out of 172 (23.83%) uterine swab samples were positive for T. pyogenes. Isolates of mastitic milk harbored the highest prevalence of resistance toward gentamicin (100%), penicillin (100%), ampicillin (90.62%), amoxicillin (87.50%) and trimethoprim-sulfamethoxazole (87.50%), while those of metritis harbored the highest prevalence of resistance toward ampicillin (100%), amoxicillin (100%), gentamicin (97.56%), penicillin (97.56%) and cefalexin (97.56%). AacC, aadA1, aadA2 and tetW were the most generally perceived antibiotic resistance genes. All bacteria harbored plo (100%) and fimA (100%) virulence factors. NanP, nanH, fimC and fimE were also the most generally perceived virulence factors.

Conclusions

All bacteria harbored plo and fimA virulence factors which showed that they can use as specific genetic markers with their important roles in pathogenicity of T. pyogenes bacteria. Phenotypic pattern of antibiotic resistance was confirmed by genotypic characterization of antibiotic resistance genes.

Pathogenicity and Virulence of Trueperella pyogenes: A Review

Bacteria from the species Trueperella pyogenes are a part of the biota of skin and mucous membranes of the upper respiratory, gastrointestinal, or urogenital tracts of animals, but also, opportunistic pathogens. T. pyogenes causes a variety of purulent infections, such as metritis, mastitis, pneumonia, and abscesses, which, in livestock breeding, generate significant economic losses. Although this species has been known for a long time, many questions concerning the mechanisms of infection pathogenesis, as well as reservoirs and routes of transmission of bacteria, remain poorly understood. Pyolysin is a major known virulence factor of T. pyogenes that belongs to the family of cholesterol-dependent cytolysins. Its cytolytic activity is associated with transmembrane pore formation. Other putative virulence factors, including neuraminidases, extracellular matrix-binding proteins, fimbriae, and biofilm formation ability, contribute to the adhesion and colonization of the host tissues. However, data about the pathogen–host interactions that may be involved in the development of T. pyogenes infection are still limited. The aim of this review is to present the current knowledge about the pathogenic potential and virulence of T. pyogenes.

Determination of the expression of three fimbrial subunit proteins in cultured Trueperella pyogenes

Background

Trueperella pyogenes is a commensal and a significant opportunistic pathogen in animals. A variety of identified or putative virulence factors are considered to significantly contribute to the occurrence of T. pyogenes infection in different species. However, these virulence factors are not fully understood.

Results

In the current study, the genes encoding putative fimbrial proteins, i.e. Fim A, Fim C, and Fim E, were cloned. Recombinant Fim A (rFim A), Fim C (rFim C), and Fim E (rFim E) were prepared and used to generate rabbit anti-rFim A, anti-rFim C, and anti-rFim E serum, respectively. Using these sera, we found that only Fim E was constitutively expressed in T. pyogenes. The expression level of Fim E in T. pyogenes peaked within 6–10 h of culture period in pH 7.5. Fim E protein expression was unaffected by anaerobic condition, but was inhibited by the microaerophilic condition. Tube agglutination tests indicated that Fim E was exhibited on the surface of T. pyogenes cells because anti-rFim E serum caused strong agglutination. Additionally, the blots for Fim A detection showed nonspecific reactions. Furthermore, the tube agglutination tests showed that anti-Fim A serum failed to cause agglutination of T. pyogenes cells, which indicated that Fim A was not, or poorly, expressed in cultured T. pyogenes. Anti-rFim C serum caused strong agglutination. However, the blots for Fim C detection showed a strong nonspecific reaction. Thus, the expression of Fim C was difficult to be determined using the current method.

Conclusions

Fim E was expressed in cultured T. pyogenes. However, Fim A was either not or poorly expressed in cultured T. pyogenes. Moreover, Fim C expression was not determined using the current strategy.

Electronic supplementary material

The online version of this article (10.1186/s13028-018-0407-3) contains supplementary material, which is available to authorized users.

Genomic characterisation, detection of genes encoding virulence factors and evaluation of antibiotic resistance of Trueperella pyogenes isolated from cattle with clinical metritis

Trueperella pyogenes is one of the most important microorganisms causing metritis in post-partum cattle. Co-infection with other bacterial species such as Escherichia coli or Fusobacterium necrofurom increases the severity of the disease and the persistence of bacteria in utero. The aim of this study was to investigate the frequency of T. pyogenes strains, and their virulence and antimicrobial resistant profiles in metritis cases. The study was carried out on 200 samples obtained from metritis discharges of postpartum cattle on 18 farms around Tehran, Iran. Sixty-five T. pyogenes isolates (32.5%) were identified, of which 16 isolates were detected as pure cultures and the other 49 isolates from cultures most commonly mixed with E. coli or F. necrofurom. In terms of diversity in biochemical characteristic of T. pyogenes strains, 8 different biotypes were identified among the isolates. Single or multi antimicrobial resistance was observed in 48 isolates (73.9%), which was mostly against trimethoprim sulfamethoxazole, azithromycin, erythromycin and streptomycin. The tetracycline resistance gene tetW and macrolide resistance genes ermB and ermX were detected in 30, 18 and 25 isolates, respectively. In the screening of genes encoding virulence factors, fimA and plo genes were identified in all tested isolates. Genes encoding nanP, nanH, fimC, fimG, fimE and cbpA were detected in 50, 54, 45, 40, 50 and 37 of isolates, respectively. Thirteen different genotypes were observed in these T. pyogenes isolates. A significant association between clonal types and virulence factor genes, biochemical profile, CAMP test result, severity of the disease and sampling time was detected.

A HEADACHE FROM OUR PAST? INTRACRANIAL ABSCESS DISEASE, VIRULENCE FACTORS OF TRUEPERELLA PYOGENES, AND A LEGACY OF TRANSLOCATING WHITE-TAILED DEER ( ODOCOILEUS VIRGINIANUS)

Trueperella pyogenes, a bacterial opportunistic pathogen residing along the skin layer of apparently healthy animals, is the etiologic agent of intracranial abscessation-suppurative meningoencephalitis, a cause of mortality for male white-tailed deer ( Odocoileus virginianus). Occurrence of this disease has been speculated to be influenced by virulence of T. pyogenes residing on white-tailed deer in geographically distinct metapopulations. To determine if differences in virulence potential of T. pyogenes could affect occurrence of disease across populations, we examined if frequency of seven virulence genes of T. pyogenes from forehead swabs of 186 apparently healthy white-tailed deer differed between sites in the state of Georgia, US, where ≥1 male tested positive for a cranial abscess and sites where no individuals tested positive for a cranial abscess. We detected six of seven virulence genes more frequently at sites where we detected ≥1 male with a cranial abscess compared to sites where we did not detect any individuals with a cranial abscess ( nanH, P<0.001; nanP, P=0.007; fimA, P<0.001; fimC, P=0.037; fimE, P<0.009; fimG, P<0.001; and cbpA, P=0.872). Our findings suggest differences in the pathogenic potential of T. pyogenes at individual sites may help to explain spatial variability of this disease. Anecdotally, the incidence of cranial abscess disease in Georgia seems to be associated with areas that were restocked with white-tailed deer from a high-fenced property in Wisconsin, US. Given the spatial distribution of this disease, we speculate that these genetic differences in T. pyogenes may have arisen from white-tailed deer restocking efforts, and our observations may be a legacy of an introduced disease manifesting itself generations later.

Binding to type I collagen is essential for the infectivity of Vibrio parahaemolyticus to host cells

Vibrio parahaemolyticus is a globally present marine bacterium that often leads to acute gastroenteritis. Two type III secretion systems (T3SSs), T3SS1 and T3SS2, are important for host infection. Type I collagen is a component of the extracellular matrix and is abundant in the small intestine. However, whether type I collagen serves as the cellular receptor for V. parahaemolyticus infection of host cells remains enigmatic. In this study, we discovered that type I collagen is not only important for the attachment of V. parahaemolyticus to host cells but is also involved in T3SS1-dependent cytotoxicity. In addition, 2 virulence factors, MAM7 and VpadF enable V. parahaemolyticus to interact with type I collagen and mediate T3SS2-dependent host cell invasion. Type I collagen, the collagen receptor α1 integrin, and its downstream factor phosphatidylinositol 3-kinase (PI3K) are responsible for V. parahaemolyticus invasion of host cells. Further biochemical studies revealed that VpadF mainly relies on the C-terminal region for type I collagen binding and MAM7 relies on mce domains to bind to type I collagen. As MAM7 and/or VpadF homologues are widely distributed in the genus Vibrio, we propose that Vibrios have evolved a unique strategy to infect host cells by binding to type I collagen.

Phenotypic and genotypic characteristics of Trueperella pyogenes isolated from ruminants

Trueperella pyogenes is an opportunistic pathogen that causes suppurative infections in animals including humans. Data on phenotypic and genotypic properties of T. pyogenes isolated from ruminants, particularly goats and sheep, are lacking. We characterized, by phenotypic and genotypic means, T. pyogenes of caprine and ovine origin, and established their phylogenetic relationship with isolates from other ruminants. T. pyogenes isolates ( n = 50) from diagnostic specimens of bovine ( n = 25), caprine ( n = 19), and ovine ( n = 6) origin were analyzed. Overall, variable biochemical activities were observed among the T. pyogenes isolates. The fimbriae-encoding gene, fimE, and neuraminidase-encoding gene, nanH, were, respectively, more frequently detected in the large ( p = 0.0006) and small ( p = 0.0001) ruminant isolates. Moreover, genotype V ( plo/ nanH/ nanP/ fimA/ fimC) was only detected in the caprine and ovine isolates, whereas genotype IX ( plo/ nanP/ fimA/ fimC/ fimE) was solely present in the isolates of bovine origin ( p = 0.0223). The 16S rRNA gene sequences of all T. pyogenes isolates were clustered with the reference T. pyogenes strain ATCC 19411 and displayed a high degree of identity to each other. Our results highlight phenotypic and genotypic diversity among ruminant isolates of T. pyogenes and reinforce the importance of characterization of more clinical isolates to better understand the pathogenesis of this bacterium in different animal species.

Bovine Endometrial Epithelial Cells Scale Their Pro-inflammatory Response In vitro to Pathogenic Trueperella pyogenes Isolated from the Bovine Uterus in a Strain-Specific Manner

Among different bacteria colonizing the bovine uterus, Trueperella pyogenes is found to be associated with clinical endometritis (CE). The ability of cows to defend against T. pyogenes infections depends on the virulence of invading bacteria and on the host's innate immunity. Therefore, to gain insights into bacterial factors contributing to the interplay of this host pathogen, two strains of T. pyogenes were included in this study: one strain (TP2) was isolated from the uterus of a postpartum dairy cow developing CE and a second strain (TP5) was isolated from a uterus of a healthy cow. The two strains were compared in terms of their metabolic fingerprints, growth rate, virulence gene transcription, and effect on bovine endometrial epithelial cells in vitro. In addition, the effect of the presence of peripheral blood mononuclear cells (PBMCs) on the response of endometrial epithelial cells was evaluated. TP2, the strain isolated from the diseased cow, showed a higher growth rate, expressed more virulence factors (cbpA, nanH, fimE, and fimG), and elicited a higher mRNA expression of pro-inflammatory factors (PTGS2, CXCL3, and IL8) in bovine endometrial epithelial cells compared with TP5, the strain isolated from the healthy cow. The presence of PBMCs amplified the mRNA expression of pro-inflammatory factors (PTGS2, CXCL3, IL1A, IL6, and IL8) in bovine endometrial epithelial cells co-cultured with live TP2 compared with untreated cells, especially as early as after 4 h. In conclusion, particular strain characteristics of T. pyogenes were found to be important for the development of CE. Furthermore, immune cells attracted to the site of infection might also play an important role in up-regulation of the pro-inflammatory response in the bovine uterus and thus significantly contribute to the host-pathogen interaction.

Identification of fimbrial subunits in the genome of Trueperella pyogenes and association between serum antibodies against fimbrial proteins and uterine conditions in dairy cows

Understanding the role of fimbrial subunits during bacterial adherence and the host's immunological response against anchorage proteins is critical for the development of strategies to prevent pathogens from thriving. The objectives of the present study were to locate fimbria-related proteins in the genome of Trueperella pyogenes (CP007519), define their importance for bacterial adherence, and evaluate the association between serum antibodies against fimbrial subunits and uterine health in dairy cows. Using a BLASTp search through the GenBank database, 4 putative clusters for fimbrial assembly were identified in the genome of T. pyogenes, namely FimA, FimC, FimE, and the novel major fimbriae FimJ. The fimbrial proteins FimA, FimC, FimE, and surface-anchored protein (SAP) were cloned into the pET 26b (+) vector, expressed in Escherichia coli BL21, and purified using affinity chromatography. Serum antibodies against FimA, FimC, FimE, and SAP were determined by ELISA on d 260±3 of gestation and at 2±1 and 35±3 d in milk (DIM) to assess the relationship between antigenicity against fimbrial proteins and parameters of uterine health. Antibodies against FimC and FimE were greater both pre- and postpartum in cows from which T. pyogenes was recovered by uterine flushing at 35±3 DIM, whereas T. pyogenes infection was not associated with differences in serum concentrations of FimA and SAP antibodies. Likewise, concentrations of FimC antibodies were consistently greater in cows diagnosed with clinical endometritis at 35±3 DIM compared with healthy counterparts. These results suggest that fimbrial proteins evaluated in the present study, particularly FimC and FimE, are important for maintenance of T. pyogenes in the uterus postpartum and development of uterine diseases in dairy cattle. Additional research is warranted to elucidate the mechanisms by which each fimbrial subunit contributes to the establishment of uterine diseases, evaluate its effect on fertility responses, and assess its relevance as a target for vaccine development.

Relationships between antimicrobial resistance, distribution of virulence factor genes and the origin of Trueperella pyogenes isolated from domestic animals and European bison (Bison bonasus)

Trueperella pyogenes is an opportunistic pathogen causing suppurative infections in livestock and wild animals. Although this bacterium is known for a long time, our knowledge about its pathogenicity is still insufficient. In this study the relationships between antimicrobial resistance profiles, distribution of virulence factor genes and the origin of T. pyogenes isolates were investigated. Isolates (n = 97) from various infections in domestic animals and European bison were studied. Minimal inhibitory concentrations of 12 antimicrobials were determined by a strip diffusion method, and PCR was used for detection of genes encoding seven putative virulence factors. All strains were susceptible to tested beta-lactams, and a statistically significant correlation between the resistance to enrofloxacin, tetracycline, macrolides, clindamycin, and a strain origin was found. The isolates from European bison were more susceptible than those from livestock, however the resistance to tetracycline and fluoroquinolones was observed. The plo and fimA genes were detected in all strains. There was no statistically significant association between the distribution of particular virulence factor genes and the type of infection, but the nanH, nanP and fimG genes were less frequently found in the isolates from European bison. The presence of three genes, nanP, nanH and cbpA, was found to be related to the resistance to tetracycline and ciprofloxacin. In conclusion, the resistance patterns of T. pyogenes were correlated with an isolate origin, but our findings did not allow to indicate which of the putative virulence factors may play a crucial role in the pathogenesis of particular types of T. pyogenes infection.

Isolation and genotypic characterization of Trueperella (Arcanobacterium) pyogenes recovered from active cranial abscess infections of male white-tailed deer (Odocoileus virginianus)

Trueperella (Arcanobacterium) pyogenes is a causative agent of suppurative infections in domestic and wild animals. In some populations of captive or free-ranging white-tailed deer (Odocoileus virginianus), cranial abscess disease is an important source of mortality in adult males. Although the pathogenesis of this disease is poorly understood, T. pyogenes has been isolated from active infections with other opportunistic bacteria. In this study, bacteria associated with cranial abscess infections were identified, the prevalence of T. pyogenes associated with these infections was determined, and the presence of known virulence determinants in T. pyogenes isolates was ascertained. Using routine biochemical techniques seven bacterial species were identified from 65 samples taken from active cranial abscess infections of 65 male white-tailed deer. Trueperellapyogenes was recovered from 46 samples; in 32 samples it was the only bacterium species detected. Staphylococcus aureus was detected in 26 samples. From these samples, the presence of known and putative virulence genes of T. pyogenes--plo, nanH, nanP, cbpA, fimA, fimC, fimE, and fimG--was examined by conventional polymerase chain reaction. All T. pyogenes isolates were positive for the pyolysin genes plo, nanP, and fimA. Furthermore, nanH, fimA, fimC, and fimE were detected in over 70% of isolates. Of the isolates tested, 48% had genotypes containing all virulence genes except cbpA. The suggestive virulence potential of all isolates, coupled with the large number of pure cultures obtained, implies that T. pyogenes is a causative agent of cranial abscess disease.

Draft Genome Sequence of Trueperella pyogenes, Isolated from the Infected Uterus of a Postpartum Cow with Metritis

Trueperella pyogenes is a common commensal bacterium and an opportunistic pathogen associated with chronic purulent disease, particularly in ruminants. We report here the genome sequence of a T. pyogenes isolate from a severe case of bovine metritis. This is the first full record of a T. pyogenes genome.

Identification of a collagen type I adhesin of Bacteroides fragilis

Bacteroides fragilis is an opportunistic pathogen which can cause life threatening infections in humans and animals. The ability to adhere to components of the extracellular matrix, including collagen, is related to bacterial host colonisation. Collagen Far Western analysis of the B. fragilis outer membrane protein (OMP) fraction revealed the presence two collagen adhesin bands of ∼ 31 and ∼ 34 kDa. The collagen adhesins in the OMP fraction were separated and isolated by two-dimensional SDS-PAGE and also purified by collagen affinity chromatography. The collagen binding proteins isolated by both these independent methods were subjected to tandem mass spectroscopy for peptide identification and matched to a single hypothetical protein encoded by B. fragilis NCTC 9343 (BF0586), conserved in YCH46 (BF0662) and 638R (BF0633) and which is designated in this study as cbp1 (collagen binding protein). Functionality of the protein was confirmed by targeted insertional mutagenesis of the cbp1 gene in B. fragilis GSH18 which resulted in the specific loss of both the ∼ 31 kDa and the ∼ 34 kDa adhesin bands. Purified his-tagged Cbp1, expressed in a B. fragilis wild-type and a glycosylation deficient mutant, confirmed that the cbp1 gene encoded the observed collagen adhesin, and showed that the 34 kDa band represents a glycosylated version of the ∼ 31 kDa protein. Glycosylation did not appear to be required for binding collagen. This study is the first to report the presence of collagen type I adhesin proteins in B. fragilis and to functionally identify a gene encoding a collagen binding protein.

In vitro and in vivo expression of virulence genes in Trueperella pyogenes based on a mouse model

Trueperella pyogenes is an important opportunistic pathogen causing a number of pyogenic infections in ruminants and other animals. This microorganism expresses several extracellular virulence proteins that contribute to its pathogenic potential. To investigate the expression levels of haemolytic exotoxin pyolysin, neuraminidases, collagen-binding protein and fimbriae of T. pyogenes in routine culture and infection process, 10 T. pyogenes isolates which simultaneously harbored ftsY, plo, cbpA, fimA, fimC, nanP, and nanH genes were injected into 10/group Kunming (KM) mice to determine their virulence. In vitro expressions of these genes were determined by quantitative PCR. Subsequently, three typical isolates including an avirulent, a moderately virulent and a strongly virulent isolate were respectively injected into mouse model to determine the in vivo expression of these genes. Finally, significant correlation was observed between collagen-binding protein, neuraminidases, and fimbriae. The expression level of pyolysin was negatively correlated with the survival of injected mice. The time course of virulence gene expression was monitored based on the expression of virulence genes in mouse model. In conclusion, the in vitro and in vivo gene expression study showed a clear difference in virulence gene expression between virulent and non-virulent isolates.

Virulence determinants and biofilm production among Trueperella pyogenes recovered from abscesses of captive forest musk deer

Trueperella pyogenes (formerly Arcanobacterium) is commonly isolated from domesticated or wild ruminants as an opportunistic pathogen. To investigate the role of virulence determinants (VDs) and biofilm production in T. pyogenes isolates, a total of 36 T. pyogenes were collected from abscesses of forest musk deer in Miyaluo Farm (Sichuan Province, China). The prevalence of VDs and associations with clonal types, antibiotic resistance and biofilm production were analyzed by PCR and bioassay. Finally, T. pyogenes isolates were separated into three clonal types based on the DNA fingerprinting of BOX-PCR. Isolates with less VDs obtained from sick forest musk deer were mainly belonged to Type 1, and the isolates with robust VD repertoire obtained from dead forest musk deer were included in Type 3. Accordingly, resistant isolates exhibited significant lower virulence than susceptible ones. Majority of T. pyogenes isolates of this study were capable of producing a biofilm. However, no VDs presence and antibiotic resistance were statistically associated with biofilm production. In conclusion, the current study demonstrated that T. pyogenes was probably the primary pathogen of abscesses in the forest musk deer. Moreover, as an animal origin pathogen, the increasing resistance of T. pyogenes isolates could also associate with a decreased virulence.

Genotypic characterization and evaluation of an antibiotic resistance of Trueperella pyogenes (Arcanobacterium pyogenes) isolated from milk of dairy cows with clinical mastitis

Trueperella pyogenes, recently reclassified from the genus Arcanobacterium, is considered the causative agent of acute suppurative mastitis called summer mastitis. T. pyogenes produces a variety of known and putative virulence factors that include pyolysin and factors promoting adhesion to host cells. The objective of this study was to report the presence of virulence genes in T. pyogenes isolates that were identified as etiological agents of clinical mastitis in cows, as well as to determine antimicrobial resistance and distribution of selected determinants that can be associated with phenotypic resistance among these isolates. The presence of genes (plo, nanH, nanP, cbpA, fimA, fimC, fimE, fimG, tet(W), erm(X), erm(B)) was examined by conventional PCRs. Resistance to 10 antimicrobial agents was determined by the broth microdilution method. Among T. pyogenes isolates of bovine mastitis origin the genes encoding all virulence factors occurred. Besides pyolysin gene plo, the fimA was the only gene detected in all isolates, whereas other virulence factor genes were found with different frequencies. Phenotypic antimicrobial resistance was observed to tetracycline (85.5% isolates) and erythromycin (9.1%). Isolates non-susceptible to erythromycin simultaneously exhibited increased MIC of pirlimycin. Beta-lactams were active against isolates. We found the correlation between the presence of tetracycline and macrolide resistance genes and corresponding resistance phenotype. Genotypic characterization of a large number of T. pyogenes isolates from different herds performed in this study may be useful in explanation, which virulence factors play a significant role in the establishment of bovine mammary gland infection.

Phenotypic characteristics and virulence genotypes of Trueperella (Arcanobacterium) pyogenes strains isolated from European bison (Bison bonasus)

Trueperella (Arcanobacterium) pyogenes is an opportunistic animal pathogen, which in European bison is associated with different suppurative infections mainly of the urogenital tract. Little is known about the virulence of this bacterium and about the pathogenesis of infections. The main objective of this study was to determine phenotypic properties and virulence genotypes of the twenty-five T. pyogenes strains isolated from lesions in various tissues of free-living European bison. Classical bacteriological methods were used for phenotypic characterization. Genes encoding seven known and putative virulence factors of T. pyogenes were detected by PCR technique. Analysis of 16S rDNA partial sequences was performed to establish phylogenetic relationships of the isolated strains. All isolates showed typical morphological features of T. pyogenes and variable biochemical activity. Most of them displayed a strong positive effect in synergistic CAMP test. For all isolates the 16S rRNA gene partial sequence was identical to that of the T. pyogenes reference strain. All isolates carried the plo and fimA genes, while the nanH, nanP, cbpA, fimC and fimG genes were present in 40, 44, 12, 88 and 24% of the isolates, respectively. The T. pyogenes strains isolated from European bison represented various phenotypes and virulence genotypes, but there was no association between the investigated properties of the bacteria and the type of anatomopathological lesions from which they were isolated. These results indicate that the studied virulence factors of T. pyogenes are not significant determinants of the localization and type of infection caused by this bacterium.

Collagen adhesin-nanoparticle interaction impairs adhesin's ligand binding mechanism

BACKGROUND

Pathogenic bacteria specifically recognize extracellular matrix (ECM) molecules of the host (e.g. collagen, fibrinogen and fibronectin) through their surface proteins known as MSCRAMMs (Microbial Surface Components Recognizing Adhesive Matrix Molecules) and initiate colonization. On implantation, biomaterials easily get coated with these ECM molecules and the MSCRAMMs mediate bacterial adherence to biomaterials. With the rapid rise in antibiotic resistance, designing alternative strategies to reduce/eliminate bacterial colonization is absolutely essential.

METHODS

The Rhusiopathiae surface protein B (RspB) is a collagen-binding MSCRAMM of Erysipelothrix rhusiopathiae. It also binds to abiotic surfaces. The crystal structure of the collagen-binding region of RspB (rRspB31-348) reported here revealed that RspB also binds collagen by a unique ligand binding mechanism called "Collagen Hug" which is a common theme for collagen-binding MSCRAMMs of many Gram-positive bacteria. Here, we report the interaction studies between rRspB31-348 and silver nanoparticles using methods like gel shift assay, gel permeation chromatography and circular dichroism spectroscopy.

RESULTS

The "Collagen Hug" mechanism was inhibited in the presence of silver nanoparticles as rRspB31-348 was unable to bind to collagen. The total loss of binding was likely because of rRspB31-348 and silver nanoparticle protein corona formation and not due to the loss of the structural integrity of rRspB31-348 on binding with nanoparticles as observed from circular dichroism experiments.

GENERAL SIGNIFICANCE

Interaction of rRspB31-348 with silver nanoparticle impaired its ligand binding mechanism. Details of this inhibition mechanism may be useful for the development of antimicrobial materials and antiadhesion drugs.

Association between virulence factors of Escherichia coli, Fusobacterium necrophorum, and Arcanobacterium pyogenes and uterine diseases of dairy cows

The objective of this study was to evaluate the relationship between bacterial species-specific virulence factors (VFs) present in the uterus at 3 different stages of lactation (1-3, 8-10, and 34-36 days in milk (DIM)) and the incidence of metritis and clinical endometritis in dairy cows. The following VF genes were investigated: plo (pyolysin), cbpA (collagen-binding protein), and fimA (fimbriae expression) which are Arcanobacterium pyogenes specific; fimH (a type 1 pilus component), Escherichia coli specific; and lktA (leukotoxin), Fusobacterium necrophorum specific. Uterine swabs were collected from 111 postpartum dairy cows. PCR was used to detect the presence of plo, cbpA, fimA, fimH, and lktA genes. A. pyogenes cbpA was detected in only 5 samples and therefore was not subjected to further analysis. E. coli (fimH) was significantly associated with metritis and endometritis when detected at 1-3 DIM; F. necrophorum (lktA) was significantly associated with metritis when detected at 1-3 and 8-12 DIM and with endometritis when detected at 34-36 DIM; and A. pyogenes (fimA and plo) was associated with metritis (fimA) when detected at 1-3 DIM and endometritis (fimA and plo) when detected at 8-10 and 34-36 DIM.

Molecular identification and further characterization of Arcanobacterium pyogenes isolated from bovine mastitis and from various other origins

The present study was designed to identify phenotypically and genotypically 61 Arcanobacterium pyogenes isolated from bovine mastitis and from various other origins. The A. pyogenes isolates showed the typical cultural and biochemical properties of this species and displayed CAMP-like synergistic hemolytic activities with various indicator strains. The species identity could be confirmed genotypically by amplification and sequencing of the superoxide dismutase A encoding gene sodA of reference strains representing 8 species of genus Arcanobacterium and subsequent design of A. pyogenes sodA gene-specific oligonucleotide primer. The A. pyogenes sodA gene-specific oligonucleotide primer allowed, together with previously described A. pyogenes 16S-23S rDNA intergenic spacer region-specific oligonucleotide primer, a reliable molecular identification of all 61 A. pyogenes of various origins. The additionally performed PCR-mediated amplification of 5 known and putative virulence factor encoding genes revealed that 100, 20, 87, 75, and 98% of the A. pyogenes carried the genes plo, cbpA, nanH, nanP, and fimA, which allowed an individual strain characterization. This might help to elucidate the role the putative virulence factors play in bovine mastitis and in various other infections caused by this bacterial pathogen.

Identification of Arcanobacterium pyogenes isolated by post mortem examinations of a bearded dragon and a gecko by phenotypic and genotypic properties

The present study was designed to identify phenotypically and genotypically two Arcanobacterium (A.) pyogenes strains isolated by post mortem examinations of a bearded dragon and a gecko. The A. pyogenes strains showed the typical biochemical properties and displayed CAMP-like synergistic hemolytic activities with various indicator strains. The species identity could be confirmed genotypically by amplification and sequencing of the 16S rDNA gene and, as novel target gene, by sequencing of the beta subunit of RNA polymerase encoding gene rpoB, of both strains and of reference strains representing nine species of the genus Arcanobacterium. The species identity of the two A. pyogenes strains could additionally be confirmed by PCR mediated amplification of species specific parts of the 16S-23S rDNA intergenic spacer region, the pyolysin encoding gene plo and by amplification of the collagen-binding protein encoding gene cbpA. All these molecular targets might help to improve the future identification and further characterization of A. pyogenes which, as demonstrated in the present study, could also be isolated from reptile specimens.

Importance of the collagen adhesin ace in pathogenesis and protection against Enterococcus faecalis experimental endocarditis

Ace is an adhesin to collagen from Enterococcus faecalis expressed conditionally after growth in serum or in the presence of collagen. Here, we generated an ace deletion mutant and showed that it was significantly attenuated versus wild-type OG1RF in a mixed infection rat endocarditis model (P<0.0001), while no differences were observed in a peritonitis model. Complemented OG1RFΔace (pAT392::ace) enhanced early (4 h) heart valve colonization versus OG1RFΔace (pAT392) (P = 0.0418), suggesting that Ace expression is important for early attachment. By flow cytometry using specific anti-recombinant Ace (rAce) immunoglobulins (Igs), we showed in vivo expression of Ace by OG1RF cells obtained directly from infected vegetations, consistent with our previous finding of anti-Ace antibodies in E. faecalis endocarditis patient sera. Finally, rats actively immunized against rAce were less susceptible to infection by OG1RF than non-immunized (P = 0.0004) or sham-immunized (P = 0.0475) by CFU counts. Similarly, animals given specific anti-rAce Igs were less likely to develop E. faecalis endocarditis (P = 0.0001) and showed fewer CFU in vegetations (P = 0.0146). In conclusion, we have shown for the first time that Ace is involved in pathogenesis of, and is useful for protection against, E. faecalis experimental endocarditis.

Enterococcus faecalis was recognized as a common cause of infective endocarditis (IE) by the early 1900s. It is still third in community-onset IE, but is the second most common cause of hospital-associated IE. Complications due to E. faecalis IE include congestive heart failure, septic emboli and death and current management involves a combination of antimicrobials, often with surgery. Emergence of antimicrobial resistance has created the need for alternative strategies (such as immunoprophylaxis) that target in vivo expressed virulence-associated surface proteins. One such E. faecalis protein is Ace, which is antigenic during human IE and mediates attachment of E. faecalis cells to host extracellular matrix proteins collagen and laminin. Using a rat model, we now show that ace contributes to E. faecalis IE pathogenesis and demonstrate that Ace is expressed at high levels during IE even though produced at low levels under laboratory conditions; both active and passive immunization based on the collagen-binding domain of Ace conferred significant protection against IE. These observations, along with data that human antibodies against Ace inhibit collagen adherence of E. faecalis, indicate that Ace is an important virulence-associated factor and a promising target for prophylactic and possibly therapeutic strategies against E. faecalis IE.

Genomic characterization of Arcanobacterium pyogenes isolates recovered from the uterus of dairy cows with normal puerperium or clinical metritis

Arcanobacterium pyogenes is considered to be the most relevant bacterium involved in the establishment of puerperal uterine infection in cattle due to its persistence in utero, resistance to treatment and synergic action with Gram negative anaerobes. Once the infection is established, A. pyogenes is responsible for the persistence of the infection. The objective of this study was to characterize A. pyogenes field isolates recovered from the uterus of cows with either normal puerperium or clinical metritis, in an attempt to identify factors that might be associated with the establishment and persistence of the disease. This characterization was based on BOX-PCR typing and on screening of eight virulence factor genes (plo, nanP, nanH, cbpA, fimA, fimC, fimE, fimG) by conventional PCR. Finally, a relationship between clonal types, virulence factors and presence of disease was investigated. A. pyogenes clonal types identified from isolates recovered from the uterus of postpartum dairy cows differed among herds. Although some clonal types were strictly associated with the development of clinical metritis, others were identified from isolates recovered from normal puerperium and clinical metritis cows. Moreover, the presence of the eight virulence factor genes was not related with the ability to induce clinical metritis, suggesting that the type of A. pyogenes may not be a determinant factor in the development of the disease. We suggest that host intrinsic factors, the synergism between A. pyogenes and other bacteria and the differential gene expression of virulence factor genes may play a more relevant role in the establishment of puerperal uterine infections.

Functional and structural properties of CbpA, a collagen-binding protein from Arcanobacterium pyogenes

Arcanobacterium pyogenes, an opportunistic pathogen of economically important food animals, is the causative agent of liver abscesses in feedlot cattle, osteomyelitis in turkeys, and pneumonia and arthritis in pigs. Previous studies identified the first A. pyogenes adhesin, CbpA, a protein located on the bacterial surface which has the ability to bind collagen and promotes adhesion to the host cells. The protein has an N-terminal ligand-binding region (region A) and a C-terminal repetitive domain (region B). In this study we found that CbpA bound to almost all the collagen types tested but not to other proteins, and it displayed a propensity to interact with several collagenous peptides derived by CNBr cleavage of type I and II collagens. The K(D) values of CbpA for type I and II collagens and collagen peptides determined by solid-phase binding assay and intrinsic tryptophan fluorescence were in the range of 1-15 nM. It was also found that CbpA and its A region bound fibronectin, and that collagen and fibronectin interacted with distinct subsites. Anti-CbpA antibodies were effective at inhibiting both binding of isolated CbpA and bacterial adhesion to immobilized collagen, suggesting that CbpA is a functional collagen-binding adhesin. Analysis of the immunological cross-reactivity of CbpA with antibodies against other bacterial collagen-binding proteins indicated that CbpA is immunologically related to ACE from Enterococcus faecalis but not to CNA from Staphylococcus aureus or Acm from Enterococcus faecium. Far-UV and near-UV circular dichroism spectra showed that full-length CbpA and its region A are mainly composed of beta-sheet with only a minor alpha-helical component and that both the proteins have a well-defined tertiary structure.

The role of laterally transferred genes in adaptive evolution

Background

Bacterial genomes develop new mechanisms to tide them over the imposing conditions they encounter during the course of their evolution. Acquisition of new genes by lateral gene transfer may be one of the dominant ways of adaptation in bacterial genome evolution. Lateral gene transfer provides the bacterial genome with a new set of genes that help it to explore and adapt to new ecological niches.

Methods

A maximum likelihood analysis was done on the five sequenced corynebacterial genomes to model the rates of gene insertions/deletions at various depths of the phylogeny.

Results

The study shows that most of the laterally acquired genes are transient and the inferred rates of gene movement are higher on the external branches of the phylogeny and decrease as the phylogenetic depth increases. The newly acquired genes are under relaxed selection and evolve faster than their older counterparts. Analysis of some of the functionally characterised LGTs in each species has indicated that they may have a possible adaptive role.

Conclusion

The five Corynebacterial genomes sequenced to date have evolved by acquiring between 8 – 14% of their genomes by LGT and some of these genes may have a role in adaptation.

Multiple genetic elements carry the tetracycline resistance gene tet(W) in the animal pathogen Arcanobacterium pyogenes

The tet(W) gene is associated with tetracycline resistance in a wide range of bacterial species, including obligately anaerobic rumen bacteria and isolates from the human gut and oral mucosa. However, little is known about how this gene is disseminated and the types of genetic elements it is carried on. We examined tetracycline-resistant isolates of the animal commensal and opportunistic pathogen Arcanobacterium pyogenes, all of which carried tet(W), and identified three genetic elements designated ATE-1, ATE-2, and ATE-3. These elements were found in 25%, 35%, and 60% of tetracycline-resistant isolates, respectively, with some strains carrying both ATE-2 and ATE-3. ATE-1 shows characteristics of a mobilizable transposon, and the tet(W) genes from strains carrying this element can be transferred at low frequencies between A. pyogenes strains. ATE-2 has characteristics of a simple transposon, carrying only the resistance gene and a transposase, while in ATE-3, the tet(W) gene is associated with a streptomycin resistance gene that is 100% identical at the DNA level with the aadE gene from the Campylobacter jejuni plasmid pCG8245. Both ATE-2 and ATE-3 show evidence of being carried on larger genetic elements, but conjugation to other strains was not observed under the conditions tested. ATE-1 was preferentially associated with A. pyogenes strains of bovine origin, while ATE-2 and ATE-3 elements were primarily found in porcine isolates, suggesting that these elements may circulate in different environments. In addition, four alleles of the tet(W) gene, primarily associated with different elements, were detected among A. pyogenes isolates.

Arcanobacterium pyogenes: molecular pathogenesis of an animal opportunist

Arcanobacterium pyogenes is a commensal and an opportunistic pathogen of economically important livestock, causing diseases as diverse as mastitis, liver abscessation and pneumonia. This organism possesses a number of virulence factors that contribute to its pathogenic potential. A. pyogenes expresses a cholesterol-dependent cytolysin, pyolysin, which is a haemolysin and is cytolytic for immune cells, including macrophages. Expression of pyolysin is required for virulence and this molecule is the most promising vaccine candidate identified to date. A. pyogenes also possesses a number of adherence mechanisms, including two neuraminidases, the action of which are required for full adhesion to epithelial cells, and several extracellular matrix-binding proteins, including a collagen-binding protein, which may be required for adhesion to collagen-rich tissue. A. pyogenes also expresses fimbriae, which are similar to the type 2 fimbriae of Actinomyces naeslundii, and forms biofilms. However, the role of these factors in the pathogenesis of A. pyogenes infections remains to be elucidated. A. pyogenes also invades and survives within epithelial cells and can survive within J774A.1 macrophages for up to 72 h, suggesting an important role for A. pyogenes interaction with host cells during pathogenesis. The two component regulatory system, PloSR, up-regulates pyolysin expression and biofilm formation but down-regulates expression of proteases, suggesting that it may act as a global regulator of A. pyogenes virulence. A. pyogenes is a versatile pathogen, with an arsenal of virulence determinants. However, most aspects of the pathogenesis of infection caused by this important opportunistic pathogen remain poorly characterized.

Sequence analysis of the plasmid genome of the probiotic strain Lactobacillus paracasei NFBC338 which includes the plasmids pCD01 and pCD02

Lactobacillus paracasei NFBC338 is a probiotic strain that was isolated from the human gastrointestinal tract (GIT) and contains a plasmid genome of 80kb. Using a shotgun sequencing approach, two of the plasmids, pCD01 (19,882bp) and pCD02 (8554bp) have been completely sequenced, and four contiguous sequences (Contigs) have been assembled. Bioinformatic analysis of pCD01 revealed that it contains 23 putative open reading frames (ORFs) and that it contains regions characterised by potential replication functions and multidrug resistance (MDR). In contrast, the content of pCD02 is mainly cryptic, although, it does contain two insertion sequence (IS) elements. Indeed, up to 17% of the entire plasmid genome encodes putative transposable elements. In addition, there are a number of interesting ORFs distributed over the four Contigs that show significant homology to genes such as those involved in adherence and biotin metabolism, which may prove beneficial to Lb. paracasei NFBC338 under certain environmental conditions. This study provides a novel insight into the rich plasmid complement of this probiotic Lactobacillus strain, which may potentially be exploited as the basis for development of improved genetic tools for probiotic lactobacilli.

Complete genome sequence and analysis of the multiresistant nosocomial pathogen Corynebacterium jeikeium K411, a lipid-requiring bacterium of the human skin flora

Corynebacterium jeikeium is a "lipophilic" and multidrug-resistant bacterial species of the human skin flora that has been recognized with increasing frequency as a serious nosocomial pathogen. Here we report the genome sequence of the clinical isolate C. jeikeium K411, which was initially recovered from the axilla of a bone marrow transplant patient. The genome of C. jeikeium K411 consists of a circular chromosome of 2,462,499 bp and the 14,323-bp bacteriocin-producing plasmid pKW4. The chromosome of C. jeikeium K411 contains 2,104 predicted coding sequences, 52% of which were considered to be orthologous with genes in the Corynebacterium glutamicum, Corynebacterium efficiens, and Corynebacterium diphtheriae genomes. These genes apparently represent the chromosomal backbone that is conserved between the four corynebacteria. Among the genes that lack an ortholog in the known corynebacterial genomes, many are located close to transposable elements or revealed an atypical G+C content, indicating that horizontal gene transfer played an important role in the acquisition of genes involved in iron and manganese homeostasis, in multidrug resistance, in bacterium-host interaction, and in virulence. Metabolic analyses of the genome sequence indicated that the "lipophilic" phenotype of C. jeikeium most likely originates from the absence of fatty acid synthase and thus represents a fatty acid auxotrophy. Accordingly, both the complete gene repertoire and the deduced lifestyle of C. jeikeium K411 largely reflect the strict dependence of growth on the presence of exogenous fatty acids. The predicted virulence factors of C. jeikeium K411 are apparently involved in ensuring the availability of exogenous fatty acids by damaging the host tissue.