Presence Of Pili Research Articles

A Literature Review on the Use of Aortic Allografts in Modern Cardiac Surgery for the Treatment of Infective Endocarditis: Is There Clear Evidence or Is It Merely a Perception?

Infective valve endocarditis is caused by different pathogens and 60% of those involve the aortic valve with valve failure. Although S. aureus is recognized as the most frequently isolated causative bacterium associated with IE in high-income countries, Gram-positive cocci nevertheless play a crucial role in promoting infection in relation to their adhesive matrix molecules. The presence of pili on the surface of Gram-positive bacteria such as in different strains of Enterococcus faecalis and Streptococcus spp., grants these causative pathogens a great offensive capacity due to the formation of biofilms and resistance to antibiotics. The indications and timing of surgery in endocarditis are debated as well as the choice of the ideal valve substitute to replace the diseased valve(s) when repair is not possible. We reviewed the literature and elaborated a systematic approach to endocarditis management based on clinical, microbiological, and anatomopathological variables known to affect postoperative outcomes with the aim to stratify the patients and orient decision making. From this review emerges significant findings on the risk of infection in the allograft used in patients with endocarditis and no endocarditis etiology suggesting that the use of allografts has proved safety and effectiveness in patients with both pathologies.

Adhesion of Lactobacillus rhamnosus GG surface biomolecules to milk proteins

Lactic Acid Bacteria (LAB) are not homogeneously located in the dairy matrix and their spatial distribution seems to be controlled by the establishment of adhesive interactions between matrix components and bacterial surface biomolecules. However the mechanisms of interaction remain unknown although they constitute an interesting way of study to appreciate the interactions. The aim of this work was to understand the role of surface biomolecules in the adhesion of Lactobacillus rhamnosus GG - the most used LAB strain in food products for their health benefits to the consumer - to milk proteins. Adhesions were probed using atomic force microscopy based force spectroscopy. To this end, the wild type strain and three of its surface mutants were employed. The wild type strain interacts with the β-lactoglobulin through the pili SpaCBA. The use of LGG surface mutants revealed that other surface biomolecules as long/small exopolysaccharides and proteins are involved in adhesion with milk proteins, in a less pronounced way than pili and in absence of pili, as all other surface biomolecules are masked in presence of pili. Altogether, this study demonstrates that adhesive interactions between LGG and milk proteins are governed by the surface composition of the bacteria.

Dehalococcoides mccartyi strain DCMB5 Respires a broad spectrum of chlorinated aromatic compounds.

Polyhalogenated aromatic compounds are harmful environmental contaminants and tend to persist in anoxic soils and sediments. Dehalococcoides mccartyi strain DCMB5, a strain originating from dioxin-polluted river sediment, was examined for its capacity to dehalogenate diverse chloroaromatic compounds. Strain DCMB5 used hexachlorobenzenes, pentachlorobenzenes, all three tetrachlorobenzenes, and 1,2,3-trichlorobenzene as well as 1,2,3,4-tetra- and 1,2,4-trichlorodibenzo-p-dioxin as electron acceptors for organohalide respiration. In addition, 1,2,3-trichlorodibenzo-p-dioxin and 1,3-, 1,2-, and 1,4-dichlorodibenzo-p-dioxin were dechlorinated, the latter to the nonchlorinated congener with a remarkably short lag phase of 1 to 4 days following transfer. Strain DCMB5 also dechlorinated pentachlorophenol and almost all tetra- and trichlorophenols. Tetrachloroethene was dechlorinated to trichloroethene and served as an electron acceptor for growth. To relate selected dechlorination activities to the expression of specific reductive dehalogenase genes, the proteomes of 1,2,3-trichlorobenzene-, pentachlorobenzene-, and tetrachloroethene-dechlorinating cultures were analyzed. Dcmb_86, an ortholog of the chlorobenzene reductive dehalogenase CbrA, was the most abundant reductive dehalogenase during growth with each electron acceptor, suggesting its pivotal role in organohalide respiration of strain DCMB5. Dcmb_1041 was specifically induced, however, by both chlorobenzenes, whereas 3 putative reductive dehalogenases, Dcmb_1434, Dcmb_1339, and Dcmb_1383, were detected only in tetrachloroethene-grown cells. The proteomes also harbored a type IV pilus protein and the components for its assembly, disassembly, and secretion. In addition, transmission electron microscopy of DCMB5 revealed an irregular mode of cell division as well as the presence of pili, indicating that pilus formation is a feature of D. mccartyi during organohalide respiration.

Increase of pneumococcal serotype 19A in Italy is due to expansion of the piliated clone ST416/CC199

The emergence of Streptococcus pneumoniae serotype 19A, following use of the heptavalent pneumococcal conjugate vaccine (PCV7), has been favoured by multiple antibiotic resistance of this serotype and by other unknown factors. The aim of this study was to examine 19A isolates from invasive pneumococcal diseases (IPD) obtained before and after PCV7 implementation to ascertain which characteristics, including the presence of pili, might have favoured the emergence of this serotype in Italy. All S. pneumoniae isolates from IPD collected at the Italian National Institute of Health in the years 2001-2003 and 2006-2009 were serotyped. The 19A isolates were submitted to antimicrobial susceptibility testing by Etest and were genotyped by a combination of pulsed field gel electrophoresis (PFGE) and Multi Locus Sequence Typing (MLST). The presence of the pilus islets PI-1 and PI-2 was detected by PCR assays targeting a marker gene in each islet. The proportion of 19A isolates from IPD significantly increased from 4 % in 2001-2003 to 12 % in 2006-2009. This was largely due to the expansion of a clone characterized by sequence type (ST) 416, clonal complex (CC) 199, already present in Italy before PCV7 implementation. This clone included isolates susceptible to penicillin and containing PI-1 genes. Other CCs contributed to the emergence of serotype 19A: CC63 and CC193, already present in 2001-2003, and new-emerging CCs or clones such as CC230, CC320 and ST5204, that include drug-resistant and/or pilus-positive isolates. The expansion of serotype 19A in Italy might have been favoured not only by antibiotic resistance, but also by other bacterial factors such as the presence of pili.

Environmental Acidification Drives S. pyogenes Pilus Expression and Microcolony Formation on Epithelial Cells in a FCT-Dependent Manner

Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen responsible for a diverse variety of diseases, including pharyngitis, skin infections, invasive necrotizing fasciitis and autoimmune sequelae. We have recently shown that GAS cell adhesion and biofilm formation is associated with the presence of pili on the surface of these bacteria. GAS pilus proteins are encoded in the FCT (Fibronectin- Collagen-T antigen) genomic region, of which nine different variants have been identified so far. In the present study we undertook a global analysis of GAS isolates representing the majority of FCT-variants to investigate the effect of environmental growth conditions on their capacity to form multicellular communities. For FCT-types 2, 3, 5 and 6 and a subset of FCT-4 strains, we observed that acidification resulting from fermentative sugar metabolism leads to an increased ability of the bacteria to form biofilm on abiotic surfaces and microcolonies on epithelial cells. The higher biofilm forming capacity at low environmental pH was directly associated with an enhanced expression of the genes encoding the pilus components and of their transcription regulators. The data indicate that environmental pH affects the expression of most pilus types and thereby the formation of multicellular cell-adhering communities that assist the initial steps of GAS infection.

Immunoglobulin-mediated agglutination of and biofilm formation by Escherichia coli K-12 require the type 1 pilus fiber.

The binding of human secretory immunoglobulin A (SIgA), the primary immunoglobulin in the gut, to Escherichia coli is thought to be dependent on type 1 pili. Type 1 pili are filamentous bacterial surface attachment organelles comprised principally of a single protein, the product of the fimA gene. A minor component of the pilus fiber (the product of the fimH gene, termed the adhesin) mediates attachment to a variety of host cell molecules in a mannose inhibitable interaction that has been extensively described. We found that the aggregation of E. coli K-12 by human secretory IgA (SIgA) was dependent on the presence of the pilus fiber, even in the absence of the mannose specific adhesin or in the presence of 25 mM alpha-CH(3)Man. The presence of pilus without adhesin also facilitated SIgA-mediated biofilm formation on polystyrene, although biofilm formation was stronger in the presence of the adhesin. IgM also mediated aggregation and biofilm formation in a manner dependent on pili with or without adhesin. These findings indicate that the pilus fiber, even in the absence of the adhesin, may play a role in biologically important processes. Under conditions in which E. coli was agglutinated by SIgA, the binding of SIgA to E. coli was not increased by the presence of the pili, with or without adhesin. This observation suggests that the pili, with or without adhesin, affect factors such as cell surface rigidity or electrostatic repulsion, which can affect agglutination but which do not necessarily determine the level of bound immunoglobulin.

Attachment to and biofilm formation on abiotic surfaces by Acinetobacter baumannii: involvement of a novel chaperone-usher pili assembly system.

Acinetobacter baumannii causes severe infections in compromised patients, survives on abiotic surfaces in hospital environments and colonizes different medical devices. In this study the analysis of the processes involved in surface attachment and biofilm formation by the prototype strain 19606 was initiated. This strain attaches to and forms biofilm structures on plastic and glass surfaces, particularly at the liquid-air interface of cultures incubated stagnantly. The cell aggregates, which contain cell stacks separated by water channels, formed under different culture conditions and were significantly enhanced under iron limitation. Electron and fluorescence microscopy showed that pili and exopolysaccharides are part of the cell aggregates formed by this strain. Electron microscopy of two insertion derivatives deficient in attachment and biofilm formation revealed the disappearance of pili-like structures and DNA sequencing analysis showed that the transposon insertions interrupted genes with the highest similarity to hypothetical genes found in Pseudomonas aeruginosa, Pseudomonas putida and Vibrio parahaemolyticus. Although the products of these genes, which have been named csuC and csuE, have no known functions, they are located within a polycistronic operon that includes four other genes, two of which encode proteins related to chaperones and ushers involved in pili assembly in other bacteria. Introduction of a copy of the csuE parental gene restored the adherence phenotype and the presence of pili on the cell surface of the csuE mutant, but not that of the csuC derivative. These results demonstrate that the expression of a chaperone-usher secretion system, some of whose components appear to be acquired from unrelated sources, is required for pili formation and the concomitant attachment to plastic surfaces and the ensuing formation of biofilms by A. baumannii cells.

Phosphorylcholine decoration of lipopolysaccharide differentiates commensal Neisseriae from pathogenic strains: identification of licA-type genes in commensal Neisseriae.

Phosphorylcholine (ChoP) is a potential candidate for a plurispecific vaccine, because it is present on surface components of many mucosal organisms, including Haemophilus influenzae, Streptococcus pneumoniae and Pseudomonas aeruginosa. In addition, ChoP has been detected on pili of Neisseria meningitidis and Neisseria gonorrhoeae. In this study, we demonstrate the presence of the phosphorylcholine epitope on the lipopolysaccharides (LPSs) of several species of commensal Neisseriae (Cn), a property that differentiates commensal from the pathogenic strains of Neisseriae. In an extended survey of 78 strains, we confirmed the exclusive expression of the ChoP epitope on pili of pathogenic Neisseriae. Despite the presence of pili on Cn, which are homologous to Class II pili of N. meningitidis, they did not react with anti-ChoP antibody. This observation was further supported by the fact that 14C-labelled choline was incorporated only in the LPSs of Cn. Analysis of the LPS of N. lactamica strain NL4 revealed two distinct and interconvertible molecular species of LPS with high and low levels of reactivity with anti-ChoP antibody. In addition, on/off phase variation gave rise to frequent modulation in the levels of antibody reactivity. A concurrent modulation was also observed in the binding of C-reactive protein, CRP, a ChoP-binding reactant that is implicated in bacterial clearance. Genetic analysis showed the presence of a gene in several Cn spp. with significant sequence identity to H. influenzae licA. This gene encodes choline kinase and is also involved in phase variation of the LPS-associated ChoP in H. influenzae. In contrast, licA-like genes were not identified in the pathogenic Neisseria strains tested. They are absent from N. meningitidis strain Z2491 genome database. These data suggest that the genetic basis for ChoP incorporation in Cn LPS resembles that in H. influenzae spp. and may be distinct from that generating the ChoP epitope on pili of pathogenic Neisseriae. Further, the modulation of ChoP expression on Cn LPS, and corresponding modulation of CRP binding, has the potential to confer the property of immune avoidance and thus of persistence on mucosa.

Pilus-mediated adhesion of Neisseria meningitidis: the essential role of cell contact-dependent transcriptional upregulation of the PilC1 protein.

Pilus-mediated adherence makes an essential contribution to the pathogenesis of Neisseria meningitidis by allowing the initial localized adherence. Pili are assembled from a protein subunit called pilin. Two proteins, PilC1 and PilC2, are also key elements in the formation of pili as the production of at least one PilC protein is required for pilus assembly. In addition, PilC1 but not PilC2 modulates adhesiveness, most probably by being the adhesin. Recently, both genes have been demonstrated to be controlled by different promoters, pilC2 is expressed from a single transcription starting point (TSP), whereas pilC1 has three TSPs. One of these, PC1.1, corresponds to the unique TSP of pilC2, and two others, PC1.2 and PC1.3, are located in a region upstream of pilC1 but not pilC2. This suggests that both genes may be under the control of separate regulatory pathways. In this work, by engineering pilC1-lacZ and pilC2-lacZ transcriptional fusions, we provide evidence that expression of pilC1, but not that of pilC2, is transiently induced by bacterial cell contact. This induction required viable cells, did not need the presence of pili and relied on the expression of pilC1 from PC1.3. Destruction of this TSP by site-directed mutagenesis did not significantly diminish the piliation level or the basal expression of PilC1, but led to the loss of cell contact-dependent upregulation of pilC1 and to a dramatic decrease in bacterial adhesiveness. Taken together, these data demonstrate that cell contact-dependent upregulation of the transcription of pilC1 at PC1.3 is essential for meningococcal pilus-mediated adhesion.

Pili of Pseudomonas syringae pathovar syringae enhance initiation of bacterial epiphytic colonization of bean

SUMMARY: Pseudomonas syringae pathovar syringae R32 expresses phage-|6-specific pili that function as adhesins anchoring bacterial cells to the surface of plants. Phage-resistant piliated and non-piliated mutants were compared to the wild-type strain with regards to pellicle formation and performance during different phases of epiphytic colonization of bush bean. The degree of piliation did not affect the ability of the strains to grow on the undisturbed plant surface. The presence of pili did, however, correlate strongly with the efficiency of the strains to initiate colonization from a liquid inoculation suspension if unadsorbed bacteria were removed by rinsing. During early colonization, wild-type bacteria became virtually resistant to displacement by rinsing within 1 d after inoculation, whereas non-piliated mutant bacteria became only partly resistant within 3 d. Piliated cells formed a pellicle on the surface of stationary liquid cultures whereas non-piliated mutant strains did not. A mechanism similar to pellicle formation may be functional on the plant surface, explaining in part the difference in resistance to removal by rinsing.

Antigenic variation of pilin regulates adhesion of Neisseria meningitidis to human epithelial cells

Pili have been shown to play an essential role in the adhesion of Neisseria meningitidis to epithelial cells. However, among piliated strains, both inter- and intrastrain variability exist with respect to their degree of adhesion to epithelial cells in vitro (Virji et al., 1992). This suggests that factors other than the presence of pili per se are involved in this process. The N. meningitidis pilin subunit undergoes extensive antigenic variation. Piliated low- and high-adhesive derivatives of the same N. meningitidis strain were selected and the nucleotide sequence of the pilin gene expressed in each was determined. The highly adhesive derivatives had the same pilin sequence. The alleles encoding the pilin subunit of the low-adhesive derivatives were completely different from the one found in the high-adhesive isolates. Using polyclonal antibodies raised against one hyperadhesive variant, it was confirmed that the low-adhesive piliated derivatives expressed pilin variants antigenically different from the highly adhesive strains. The role of antigenic variation in the adhesive process of N. meningitidis was confirmed by performing allelic exchanges of the pilE locus between low- and high-adhesive isolates. Antigenic variation has been considered a means by which virulent bacteria evade the host immune system. This work provides genetic proof that a bacterial pathogen, N. meningitidis, can use antigenic variation to modulate their degree of virulence.

Q pili enhance the attachment of Moraxella bovis to bovine corneas in vitro

Moraxella bovis, the causative agent of infectious bovine keratoconjunctivitis, exhibits several virulence factors, including pili, haemolysin, leukotoxin, and proteases. The pili are filamentous appendages which mediate bacterial adherence. Prior studies have shown that Q-piliated M. bovis Epp63 are more infectious and more pathogenic than I-piliated and non-piliated isogenic variants, suggesting that Q pili per se, or traits associated with Q-pilin expression, promote the early association of Q-piliated bacteria with bovine corneal tissue. In order to better evaluate the role of Q pili in M. bovis attachment, several M. bovis strains and a recombinant P. aeruginosa strain which elaborates M. bovis Q pili but not P. aeruginosa PAK pili, were evaluated using an in vitro corneal attachment assay. For each strain tested, piliated organisms attached better than non-piliated bacteria. M. bovis Epp63 Q-piliated bacteria adhered better than either the I-piliated or non-piliated isogenic variants. Finally, recombinant P. aeruginosa organisms elaborating M. bovis Q pili adhered better than the parent P. aeruginosa strain which did not produce M. bovis pili. These results indicate that the presence of pili, especially Q pili, enhances the attachment of bacteria to bovine cornea in vitro.

Encapsulation and pilus formation of Bacteroides spp. in normal flora abscesses and blood

The presence of encapsulated and piliated Bacteroides spp. (mostly Bacteroides fragilis and melaninogenicus groups was investigated in isolates from blood, abscesses and normal flora. Of the strains of Bacteroides spp. isolated 45 of 54 (83%) recovered from blood and 31 of 40 (78%) found in abscesses were encapsulated. In contrast, only seven of 71 (10%) similar strains isolated from the faeces or pharynx of healthy persons were encapsulated (P < 0.001). Pili were observed in three of 54 (6%) of strains isolated from blood, 30 of 40 (75%) of those recovered from abscesses (P < 0.001), and 49 of 71 (69%) of those found in normal flora (P < 0.001). The predominance of encapsulated forms in all strains of B. fragilis and B. melaninogenicus in blood as well as in abscesses suggests an increased virulence of these compared with non-encapsulated isolates. In contrast, the presence of pili in Bacteroides spp. recovered mostly from abscesses and normal flora suggests that this structure may play a role in the ability of these organisms to adhere to mucous membranes and may interfere with their ability to spread systemically. These findings illustrate the morphological differences that may be observed in Bacteroides spp. from various anatomical sites.

Effect of mechanical removal of pili on gliding motility of Myxococcus xanthus.

Gliding motility of Myxococcus xanthus is governed by both the adventurous (A) and the social (S) motility gene systems. The presence of pili has previously been shown to be correlated with a genetically intact S-motility system (D. Kaiser, Proc. Natl. Acad. Sci. USA 76:5952-5956, 1979). The purpose of the present work was to study the direct effect of mechanical removal of pill on the social motility of M. xanthus. Depiliation resulted in (i) a loss of streaming motility of A- S+ mutants, i.e., strains which are able to move by virtue of the S-motility system only, (ii) no effect on motility in A+ S- mutants, i.e., strains capable of movement by the A-motility system only, and (iii) a retardation of streaming speed in the wild-type strain (A+ S+). Cell-cell cohesion, another characteristic of social behavior, was not affected by mechanical removal of pill. The observation that mechanical depiliation perturbed the motility of strains which rely on the S-motility system strongly supports a role for pili in social motility of M. xanthus.

The role of pili in the interactions of pathogenic Neisseria with cultured human endothelial cells

The influence of the two surface structures of Neisseria meningitidis, capsule and pili, in bacterial interactions with human endothelial cells was investigated. Increased association correlated with the presence of pili on bacteria while capsule type had no apparent effect. Strains expressing both Class I and Class II pili associated with endothelial cells in significantly larger numbers compared with the non-piliated variants of the same strains (greater than 10x). Variants of Neisseria gonorrhoeae strain P9 expressing antigenically distinct pili also associated with endothelial cells in larger numbers (greater than 30x) compared with the non-piliated variant. Electron microscopic studies confirmed these data and showed that gonococci were internalized more frequently compared with meningococci. One consequence of increased association was an increase in the cytopathic effect of bacteria on the target cells.

Attachment of mesophilic aeromonads to cultured mammalian cells

The interaction between mesophilic aeromonads and cultured mouse adrenal cells was examined. Preliminary experiments indicated that aeromonad attachment was dependent upon inoculum size, incubation time, and incubation temperature. Optimal attachment was observed after 30 min of incubation at 37°C with an inoculum size of 1×107 CFU. Heat-killed and formalin-treated organisms did not attach to the cultured cell system. The attachment of aeromonads to the mammalian cell surface was confirmed by light and scanning electron microscopy. Aeromonad attachment correlated both with the presence of pili and the specific aeromonad species, but not with hydrophobicity or the ability to autoagglutinate. Piliated strains were more likely to show high or moderate attachment.Aeromonas sobria, A. hydrophila, andA. veronii showed a greater ability to bind adrenal cells than didA. caviae. Removal of the pili from twoA. sobria isolates markedly reduced their attachment. In contrast, oneA. hydrophila isolate was strongly adherent after the removal of pili. The hemagglutination patterns produced byA. sobria and the other aeromonad species were distinctly different, but potentially predictive of the ability of aeromonads to attach to cultured mouse adrenal cells. These studies indicate that multiple mechanisms are important for the attachment of mesophilic aeromonads to mammalian cells. This model may prove useful for studying the pathogenesis of aeromonad infections.

Characterization of a pilus produced byAeromonas hydrophila

A pilus produced by Aeromonas hydrophila was purified and partially characterized. The pilin monomers had an apparent molecular weight of 17,000. Agglutination studies indicated serological cross-reactivity in the pili of A. hydrophila strains. Presence of pili did not correlate with hydrophobicity or haemagglutinating ability of the bacteria.

Characterization of a pilus produced by Aeromonas hydrophila

A pilus produced by Aeromonas hydrophila was purified and partially characterized. The pilin monomers had an apparent molecular weight of 17,000. Agglutination studies indicated serological cross-reactivity in the pili of A. hydrophila strains. Presence of pili did not correlate with hydrophobicity or haemagglutinating ability of the bacteria.

Surface characteristics of Pseudomonas aeruginosa grown in a chamber implant model in mice and rats

Pseudomonas aeruginosa PAO1 was grown in vivo in chambers implanted into the peritoneums of mice and rats. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracts of bacterial cells taken from the chambers and washed to remove loosely bound host proteins revealed the presence of the major outer membrane proteins D2, E, F, G, and H2. Western immunoblotting with specific antisera confirmed the presence of porin protein F and lipoprotein H2. However, there was no apparent induction of the phosphate starvation-inducible porin P or the divalent cation starvation-inducible protein H1. Small amounts of proteins with molecular weights similar to those of the iron-regulated outer membrane proteins were found in cells grown in vivo; however, their presence could not be confirmed immunologically. The presence of pili and flagella on the cells grown in vivo was demonstrated by electron microscopy and Western immunoblotting. A consistent alteration in the lipopolysaccharide banding pattern was observed after growth in vivo. Compared with cells of strain PAO1 grown in vitro, cells grown in vivo appeared to lack a series of high-molecular-weight O-antigen-containing lipopolysaccharide bands and gained a new series of lower-molecular-weight lipopolysaccharide bands. This alteration in the lipopolysaccharide after growth in vivo did not affect the O-antigen serotype or the resistance of the bacteria to serum.

Morphological differences in Neisseria meningitidis pili

Disease and carrier isolates of Neisseria meningitidis were examined for their ability to adhere to human buccal epithelial cells and human cell lines and to hemagglutinate human erythrocytes, properties thought to be associated with the presence of pili. Seventy percent (7 of 10) of carrier isolates were found to be highly adherent to human buccal epithelial cells and to agglutinate human A, B, O, Rh-, and Rh+ erythrocytes. In contrast, 60% of the disease isolates adhered poorly to human buccal epithelial cells and 80% failed to agglutinate human erythrocytes. No adherence of either disease or carrier isolates was observed when several human cell lines were tested. When the meningococcal strains were examined by electron microscopy, 7 of 10 disease isolates were found to possess large bundles of aggregated pili (alpha-type pili), while 7 of 10 carrier isolates were found to have numerous unaggregated pili (beta-type pili). A monoclonal antibody against meningococcal pili and one against gonococcal pili reacted with 6 of 10 piliated carrier isolates and 4 of 10 piliated disease isolates. These results suggest that meningococci, like gonococci, possess different types of pili which differ in morphological, antigenic, and binding properties. In addition, antigenic and morphological differences between pili from carrier and disease isolates were observed as well as differences in adherence and hemagglutinating properties.