Species of alpha-hemolytic streptococci possessing a C-polysaccharide phosphorylcholine-containing antigen

Parallel detection of multiple biomarkers in a point-of-care-competent device for the prediction of exacerbations in chronic inflammatory lung disease

Sudden aggravations of chronic inflammatory airway diseases are difficult-to-foresee life-threatening episodes for which advanced prognosis-systems are highly desirable. Here we present an experimental chip-based fluidic system designed for the rapid and sensitive measurement of biomarkers prognostic for potentially imminent asthma or COPD exacerbations. As model biomarkers we chose three cytokines (interleukin-6, interleukin-8, tumor necrosis factor alpha), the bacterial infection marker C-reactive protein and the bacterial pathogen Streptococcus pneumoniae-all relevant factors in exacerbation episodes. Assay protocols established in laboratory environments were adapted to 3D-printed fluidic devices with emphasis on short processing times, low reagent consumption and a low limit of detection in order to enable the fluidic system to be used in point-of-care settings. The final device demonstrator was validated with patient sample material for its capability to detect endogenous as well as exogenous biomarkers in parallel.

PepO and CppA modulate Streptococcus sanguinis susceptibility to complement immunity and virulence

Streptococcus sanguinis is a ubiquitous commensal species of the oral cavity commonly involved as an opportunistic pathogen in cardiovascular infections. In this study, we investigated the functions of endopeptidase O (PepO) and a C3-degrading protease (CppA) in the systemic virulence of S. sanguinis. Isogenic mutants of pepO and cppA obtained in strain SK36 showed increased susceptibility to C3b deposition and to opsonophagocytosis by human polymorphonuclear neutrophils (PMN). These mutants differ, however, in their profiles of binding to serum amyloid P component (SAP) and C1q, whereas both showed reduced interaction with C4b-binding protein (C4BP) and/or factor H (FH) regulators as compared to SK36. The two mutants showed defects in ex vivo persistence in human blood, serum-mediated invasion of HCAEC endothelial cells, and virulence in a Galleria mellonella infection model. The transcriptional activities of pepO and cppA, assessed by RT-qPCR in nine wild-type strains, further indicated strain-specific profiles of pepO/cppA expression. Moreover, non-conserved amino acid substitutions were detected among the strains, mostly in CppA. Phylogenetic comparisons with homologues of streptococcal species of the oral and oropharyngeal sites suggested that S. sanguinis PepO and CppA have independent ancestralities. Thus, this study showed that PepO and CppA are complement evasion proteins expressed by S. sanguinis in a strain-specific manner, which are required for multiple functions associated with cardiovascular virulence.

Perspective of a Pediatrician: Shared Pathogenesis of the Three Most Successful Pathogens of Children

Highly successful invasive pathogens exploit host vulnerabilities by adapting tools to co-opt highly conserved host features. This is especially true when pathogens develop ligands to hijack trafficking routes or signaling patterns of host receptors. In this context, highly successful pathogens can be grouped together by the patterns of organs infected and diseases they cause. In the case of this perspective, the focus is on the historically most successful invasive bacterial pathogens of children that cause pneumonia, sepsis and meningitis: Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. This triad shares a ligand to bind to PAF receptor to enter host cells despite early defenses by innate immunity. All three also target laminin receptor to cross endothelial barriers using a common set of molecular tools that may prove to be a design for a cross-protective vaccine.

Re-validation and update of an extended-specificity multiplex assay for detection of Streptococcus pneumoniae capsular serotype/serogroup-specific antigen and cell-wall polysaccharide in urine specimens

National surveillance of pneumococcal disease at the serotype level is essential to assess the effectiveness of vaccination programmes. We previously developed a highly sensitive extended-specificity multiplex immunoassay for detection of Streptococcus pneumoniae serotype-specific antigen in urine in the absence of isolates. The assay uses human mAbs that detect the 24 pneumococcal serotype/groups targeted by the pneumococcal conjugate vaccines (PCVs) and pneumococcal polysaccharide vaccine (PPV-23) plus some cross-reactive types and the pneumococcal cell-wall polysaccharide. However, the previous assay had some limitations, namely the reduced specificity of the serotype 7F, 20 and 22F assays, for which non-specific binding in urine samples was observed. Here we report on the further development and re-validation of a new version of the assay (version 2.1), which offers improved sensitivity towards serotypes 7F, 18C and 19F and increased specificity for serotypes 7F, 20 and 22F by replacement of some of the antibody clones with new clones. Using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease, the overall clinical sensitivity of this version of the assay based on isolation of S. pneumoniae from a normally sterile site is 94.3 % and the clinical specificity is 93.6 %, in comparison with clinical sensitivity and specificity values of 96.2 % and 89.9 % in the previous assay.

Oral streptococci show diversity in resistance to complement immunity

PURPOSE

Mechanisms underlying systemic infections by oral species of Mitis (Streptococcus mitis, Streptococcus oralis) and Sanguinis (Streptococcus gordonii, Streptococcus sanguinis) commensal streptococci are poorly understood. This study investigates profiles of susceptibility to complement-mediated host immunity in representative strains of these four species, which were isolated from oral sites or from the bloodstream.

METHODOLOGY

Deposition of complement opsonins (C3b/iC3b), and surface binding to C-reactive protein (CRP) and to IgG antibodies were quantified by flow cytometry in 34 strains treated with human serum (HS), and compared to rates of opsonophagocytosis by human PMN mediated by complement (CR1/3) and/or IgG Fc (FcγRII/III) receptors.

RESULTS

S. sanguinis strains showed reduced susceptibility to complement opsonization and low binding to CRP and to IgG compared to other species. Surface levels of C3b/iC3b in S. sanguinis strains were 4.5- and 7.8-fold lower than that observed in S. gordonii and Mitis strains, respectively. Diversity in C3b/iC3b deposition was evident among Mitis species, in which C3b/iC3b deposition was significantly associated with CR/FcγR-dependent opsonophagocytosis by PMN (P<0.05). Importantly, S. gordonii and Mitis group strains isolated from systemic infections showed resistance to complement opsonization when compared to oral isolates of the respective species (P<0.05).

CONCLUSIONS

This study establishes species-specific profiles of susceptibility to complement immunity in Mitis and Sanguinis streptococci, and indicates that strains associated with systemic infections have increased capacity to evade complement immunity. These findings highlight the need for studies identifying molecular functions involved in complement evasion in oral streptococci.

Development of an Extended-Specificity Multiplex Immunoassay for Detection of Streptococcus pneumoniae Serotype-Specific Antigen in Urine by Use of Human Monoclonal Antibodies

Current pneumococcal vaccines cover the 10 to 23 most common serotypes of the 92 presently described. However, with the increased usage of pneumococcal-serotype-based vaccines, the risk of serotype replacement and an increase in disease caused by nonvaccine serotypes remains. Serotype surveillance of pneumococcal infections relies heavily on culture techniques, which are known to be insensitive, particularly in cases of noninvasive disease. Pneumococcal-serotype-specific urine assays offer an alternative method of serotyping for both invasive and noninvasive disease. However, the assays described previously cover mainly conjugate vaccine serotypes, give little information about circulating nonvaccine serotypes, and are currently available only in one or two specialist laboratories. Our laboratory has developed a Luminex-based extended-range antigen capture assay to detect pneumococcal-serotype-specific antigens in urine samples. The assay targets 24 distinct serotypes/serogroups plus the cell wall polysaccharide (CWP) and some cross-reactive serotypes. We report that the assay is capable of detecting all the targeted serotypes and the CWP at 0.1 ng/ml, while some serotypes are detected at concentrations as low as 0.3 pg/ml. The analytical serotype specificity was determined to be 98.4% using a panel of polysaccharide-negative urine specimens spiked with nonpneumococcal bacterial antigens. We also report clinical sensitivities of 96.2% and specificities of 89.9% established using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease. This assay can be extended for testing other clinical samples and has the potential to greatly improve serotype-specific surveillance in the many cases of pneumococcal disease in which a culture is never obtained.

CovR Regulates Streptococcus mutans Susceptibility To Complement Immunity and Survival in Blood

Streptococcus mutans, a major pathogen of dental caries, may promote systemic infections after accessing the bloodstream from oral niches. In this study, we investigate pathways of complement immunity against S. mutans and show that the orphan regulator CovR (CovR_Sm) modulates susceptibility to complement opsonization and survival in blood. S. mutans blood isolates showed reduced susceptibility to C3b deposition compared to oral isolates. Reduced expression of covR_Sm in blood strains was associated with increased transcription of CovR_Sm-repressed genes required for S. mutans interactions with glucans (gbpC, gbpB, and epsC), sucrose-derived exopolysaccharides (EPS). Consistently, blood strains showed an increased capacity to bind glucan in vitro Deletion of covR_Sm in strain UA159 (UAcov) impaired C3b deposition and binding to serum IgG and C-reactive protein (CRP) as well as phagocytosis through C3b/iC3b receptors and killing by neutrophils. Opposite effects were observed in mutants of gbpC, epsC, or gtfBCD (required for glucan synthesis). C3b deposition on UA159 was abolished in C1q-depleted serum, implying that the classical pathway is essential for complement activation on S. mutans Growth in sucrose-containing medium impaired the binding of C3b and IgG to UA159, UAcov, and blood isolates but had absent or reduced effects on C3b deposition in gtfBCD, gbpC, and epsC mutants. UAcov further showed increased ex vivo survival in human blood in an EPS-dependent way. Consistently, reduced survival was observed for the gbpC and epsC mutants. Finally, UAcov showed an increased ability to cause bacteremia in a rat model. These results reveal that CovR_Sm modulates systemic virulence by regulating functions affecting S. mutans susceptibility to complement opsonization.

The mammalian complement system as an epitome of host-pathogen genetic conflicts

The complement system is an innate immunity effector mechanism; its action is antagonized by a wide array of pathogens and complement evasion determines the virulence of several infections. We investigated the evolutionary history of the complement system and of bacterial-encoded complement-interacting proteins. Complement components targeted by several pathogens evolved under strong selective pressure in primates, with selection acting on residues at the contact interface with microbial/viral proteins. Positively selected sites in CFH and C4BPA account for the human specificity of gonococcal infection. Bacterial interactors, evolved adaptively as well, with selected sites located at interaction surfaces with primate complement proteins. These results epitomize the expectation under a genetic conflict scenario whereby the host's and the pathogen's genes evolve within binding avoidance-binding seeking dynamics. In silico mutagenesis and protein-protein docking analyses supported this by showing that positively selected sites, both in the host's and in the pathogen's interacting partner, modulate binding.

Rapid identification of Streptococcus pneumoniae in blood cultures by using the ImmuLex, Slidex and Wellcogen latex agglutination tests and the BinaxNOW antigen test

Rapid identification of Streptococcus pneumoniae in blood culture (BC) bottles is important for early directed antimicrobial therapy in pneumococcal bacteraemia. We evaluated a new latex agglutination (LA) test on BC bottles, the ImmuLex™ S. pneumoniae Omni (Statens Serum Institut, Denmark), and compared the performance with the Slidex® pneumo-Kit (bioMérieux, France) and the Wellcogen™ S. pneumoniae (Remel, UK) LA tests, as well as the BinaxNOW® S. pneumoniae (Alere, USA) antigen test. The four tests were directly applied on 358 positive BC bottles with Gram-positive cocci in pairs or chains and on 15 negative bottles. Valid test results were recorded in all cases for ImmuLex and BinaxNOW and in 88.5 % (330/373) and 94.1 % (351/373) of cases for Slidex and Wellcogen, respectively. Based on bottles positive for S. pneumoniae by conventional methods, the sensitivity of ImmuLex was 99.6 %, similar to the other tests (range, 99.6-100 %). Based on bottles positive for non-pneumococcal pathogens, the specificity of ImmuLex was 82.6 %, in comparison to 97.6 % for Slidex (p < 0.01) and 85.4 % for Wellcogen (p = ns). The BinaxNOW test had a lower specificity (64.1 %) than any LA test (p < 0.01). On BC bottles positive for α-haemolytic streptococci, ImmuLex was positive in 12/67 (17.9 %) cases, Slidex in 2/59 (3.4 %) cases, Wellcogen in 11/64 (17.2 %) cases and BinaxNOW in 25/67 (37.3 %) cases. In conclusion, the ImmuLex test provides a valid and sensitive technique for the rapid detection of S. pneumoniae in BC bottles, similar to the other compared methods. However, the specificity was sub-optimal, since the test may cross-react with other Gram-positive bacteria.

Lipoteichoic acid of Streptococcus oralis Uo5: a novel biochemical structure comprising an unusual phosphorylcholine substitution pattern compared to Streptococcus pneumoniae

Members of the Mitis group of streptococci possess teichoic acids (TAs) as integral components of their cell wall that are unique among Gram-positive bacteria. Both, lipoteichoic (LTA) and wall teichoic acid, are formed by the same biosynthetic pathway, are of high complexity and contain phosphorylcholine (P-Cho) residues. These residues serve as anchors for choline-binding proteins (CBPs), some of which have been identified as virulence factors of the human pathogen Streptococcus pneumoniae. We investigated the LTA structure of its close relative Streptococcus oralis. Our analysis revealed that S. oralis Uo5 LTA has an overall architecture similar to pneumococcal LTA (pnLTA) and can be considered as a subtype of type IV LTA. Its structural complexity is even higher than that of pnLTA and its composition differs in number and type of carbohydrate moieties, inter-residue connectivities and especially the P-Cho substitution pattern. Here, we report the occurrence of a saccharide moiety substituted with two P-Cho residues, which is unique as yet in bacterial derived surface carbohydrates. Finally, we could link the observed important structural variations between S. oralis and S. pneumoniae LTA to the divergent enzymatic repertoire for their TA biosynthesis.

The Binax NOW Streptococcus pneumoniae test applied on nasopharyngeal aspirates to support pneumococcal aetiology in community-acquired pneumonia

BACKGROUND

The use of nasopharyngeal secretions to enhance diagnostic yields of pneumococcal aetiology in community-acquired pneumonia (CAP) is of interest. We evaluated the Binax NOW Streptococcus pneumoniae immunochromatographic test (ICT) on nasopharyngeal aspirates (NPA) in order to support pneumococcal aetiology in CAP.

METHODS

The NPA ICT was applied on 180 adult CAP patients and 64 healthy controls. The rate of pneumococcal detection in the nasopharynx was compared to rates for lytA polymerase chain reaction (PCR) and culture on NPA.

RESULTS

According to blood and sputum culture and urine ICT, the test sensitivity in 59 patients with a pneumococcal aetiology was 81%. The specificity was suboptimal, with 72% negative tests among CAP patients without a pneumococcal aetiology. However, the test was positive in only 11% of patients with atypical pneumonia and in 4.7% of healthy controls. The positivity rate was higher for NPA ICT compared to culture on NPA in all CAP patients, and to both PCR and culture on NPA in non-pneumococcal non-atypical CAP patients. In 113 (63%) patients with β-lactam monotherapy, cure without treatment alteration was noted more often in cases with positive compared to negative NPA ICT at admission (91% vs 69%; p < 0.01).

CONCLUSIONS

The high sensitivity and the low positivity rates in patients with atypical pneumonia and healthy controls, in combination with the correlation between positive test results and clinical cure with β-lactam therapy, may support a pneumococcal aetiology in CAP in populations with low pneumococcal carriage rates.

Microbial modulation of host immunity with the small molecule phosphorylcholine

All microorganisms dependent on persistence in a host for survival rely on either hiding from or modulating host responses to infection. The small molecule phosphorylcholine, or choline phosphate (ChoP), is used for both of these purposes by a wide array of bacterial and parasitic microbes. While the mechanisms underlying ChoP acquisition and expression are diverse, a unifying theme is the use of ChoP to reduce the immune response to infection, creating an advantage for ChoP-expressing microorganisms. In this minireview, we discuss several benefits of ChoP expression during infection as well as how the immune system fights back against ChoP-expressing pathogens.

Evaluation of a rapid immunochromatographic ODK-0901 test for detection of pneumococcal antigen in middle ear fluids and nasopharyngeal secretions

Since the incidence of penicillin-resistant Streptococcus pneumoniae has been increasing at an astonishing rate throughout the world, the need for accurate and rapid identification of pneumococci has become increasingly important to determine the appropriate antimicrobial treatment. We have evaluated an immunochromatographic test (ODK-0901) that detects pneumococcal antigens using 264 middle ear fluids (MEFs) and 268 nasopharyngeal secretions (NPSs). A sample was defined to contain S. pneumoniae when optochin and bile sensitive alpha hemolytic streptococcal colonies were isolated by culture. The sensitivity and specificity of the ODK-0901 test were 81.4% and 80.5%, respectively, for MEFs from patients with acute otitis media (AOM). In addition, the sensitivity and specificity were 75.2% and 88.8%, respectively, for NPSs from patients with acute rhinosinusitis. The ODK-0901 test may provide a rapid and highly sensitive evaluation of the presence of S. pneumoniae and thus may be a promising method of identifying pneumococci in MEFs and NPSs.

Clinical and laboratory features of Streptococcus salivarius meningitis: a case report and literature review

Streptococcus salivarius is a normal member of the human oral microbiome that is an uncommon cause of invasive infections. Meningitis is a rare but increasingly reported infection caused by S. salivarius. Despite the growing number of reported cases, a comprehensive review of the literature on S. salivarius meningitis is lacking. We sought to gain a better understanding of the clinical presentation, evaluation, management, and outcome of S. salivarius meningitis by analyzing previously reported cases. In addition to a single case reported here, 64 previously published cases of meningitis were identified for this review. The collected data confirm that most patients presented with classical signs and symptoms of bacterial meningitis with a predominance of neutrophils in the cerebrospinal fluid (CSF) and hypoglycorrhachia. The majority of cases followed iatrogenic or traumatic CSF contamination. Most cases were diagnosed by CSF culture within one day of symptom onset. There was no clear evidence of predisposing co-morbid conditions in patients with meningitis, although in most case reports, limited information was given on the medical history of each patient. Outcomes were generally favorable with antibiotic management. Clinicians should suspect S. salivarius meningitis in patients presenting acutely after medical or surgical procedures involving the meninges.

LytF, a novel competence-regulated murein hydrolase in the genus Streptococcus

Streptococcus pneumoniae and probably most other members of the genus Streptococcus are competent for natural genetic transformation. During the competent state, S. pneumoniae produces a murein hydrolase, CbpD, that kills and lyses noncompetent pneumococci and closely related species. Previous studies have shown that CbpD is essential for efficient transfer of genomic DNA from noncompetent to competent cells in vitro. Consequently, it has been proposed that CbpD together with the cognate immunity protein ComM constitutes a DNA acquisition mechanism that enables competent pneumococci to capture homologous DNA from closely related streptococci sharing the same habitat. Although genes encoding CbpD homologs or CbpD-related proteins are present in many different streptococcal species, the genomes of a number of streptococci do not encode CbpD-type proteins. In the present study we show that the genomes of nearly all species lacking CbpD encode an unrelated competence-regulated murein hydrolase termed LytF. Using Streptococcus gordonii as a model system, we obtained evidence indicating that LytF is a functional analogue of CbpD. In sum, our results show that a murein hydrolase gene is part of the competence regulon of most or all streptococcal species, demonstrating that these muralytic enzymes constitute an essential part of the streptococcal natural transformation system.

Deletion of competence-induced genes over-expressed in biofilms caused transformation deficiencies in Streptococcus mutans

Previous studies identified nine genes with increased expression in Streptococcus mutans biofilms of which six possessed putative ComX promoter sequences and were homologous to competence-induced genes in Streptococcus pneumoniae, Streptococcus gordonii and Bacillus subtilis. As competence increases in biofilms, a study was undertaken into the roles that these biofilm-induced genes might play in transformation. Only five of the nine gene deletions had a significant effect on transformation efficiency. Deletion of the genes for recombinase A, recA, DNA processing protein, dprA and single-stranded DNA-binding protein, ssbA, produced results comparable with those from other bacteria, supporting the contention that these proteins have similar functions in S. mutans competence. The uncharacterized genes SMU.769 and SMU.836 produced results in variance to deletion mutants of putative homologues in S. pneumoniae. Deletion of SMU.769 reduced chromosomal transformation 2.3-fold. SMU.769 belongs to a family of conserved genes induced by the competence-stimulating peptide and which have no established function. In contrast, deletion of SMU.836 reduced transformation of both plasmid and chromosomal DNA to <3%. Homology searches suggested that Smu.836 belongs to a family of competence-induced peptidoglycan hydrolases with a conserved enzyme domain and a species-variable cell-binding domain for which the best characterized member is the choline-binding protein D, CbpD, of S. pneumoniae.

Characterization of gene use and efficacy of mouse monoclonal antibodies to Streptococcus pneumoniae serotype 8

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia in the United States and globally. Despite the availability of pneumococcal capsular polysaccharide (PPS) and protein conjugate-based vaccines, the prevalence of antibiotic-resistant pneumococcal strains, serotype (ST) replacement in nonconjugate vaccine strains, and uncertainty as to whether the PPS vaccine that is used in adults protects against pneumonia emphasize the need for continued efforts to understand the nature of protective PPS antibody responses. In this study, we generated mouse monoclonal antibodies (MAbs) to a conjugate consisting of the PPS of serotype 8 (PPS8) S. pneumoniae and tetanus toxoid. Thirteen MAbs, including four IgMs that bound to PPS8 and phosphorylcholine (PC) and five IgMs and four IgG1s that bound to PPS8 but not PC, were produced, and their nucleotide sequences, epitope and fine specificity, and efficacy against lethal challenge with ST8 S. pneumoniae were determined. MAbs that bound to PPS8 exhibited gene use that was distinct from that exhibited by MAbs that bound to PC. Only PPS8-binding MAbs that did not bind PC were protective in mice. All 13 MAbs used germ line variable-region heavy (V(H)) and light (V(L)) chain genes, with no evidence of somatic hypermutation. Our data reveal a relationship between PPS specificity and V(H) gene use and MAb efficacy in mice. These findings provide insight into the relationship between antibody molecular structure and function and hold promise for the development of novel surrogates for pneumococcal vaccine efficacy.

Development of a sensitive, multiplexed immunoassay using xMAP beads for detection of serotype-specific streptococcus pneumoniae antigen in urine samples

In support of the surveillance of pneumococcal infections in the era of conjugate vaccines, a sensitive and specific multiplex immunoassay using xMAP beads has been developed for direct detection of pneumococcal serotype-specific polysaccharides in clinical samples, particularly urine. The assay was tested on panels of spiked urine specimens, clinical urine specimens and bacterial isolates. Each of the 14 serotypes in the multiplex assay can be detected to 0.1&emsp14;ng purified polysaccharide ml(-1), or less. Testing of a panel of urine specimens from patients with culture-confirmed pneumococcal or non-pneumococcal disease indicated that the multiplex assay is both sensitive and specific. The correct pneumococcal serotype was identified directly from urine in 46/58 (79.3 %) patients who had a contemporaneous blood culture isolate of a multiplex assay serotype. Furthermore, the specificity of the assay on this panel of samples was 99.3 % (145/146). This multiplex assay could be useful, in conjunction with the pneumococcal screening test Binax NOW, in urine for diagnosis of pneumococcal disease and the identification of the aetiological serotype, and potentially be of benefit in culture-negative patients.

Plasma lipoproteins are important components of the immune system

Plasma lipoproteins (VLDL, LDL, Lp[a] and HDL) function primarily in lipid transport among tissues and organs. However, cumulative evidence suggests that lipoproteins may also prevent bacterial, viral and parasitic infections and are therefore a component of innate immunity. Lipoproteins can also detoxify lipopolysaccharide and lipoteichoic acid. Infections can induce oxidation of LDL, and oxLDL in turn plays important anti-infective roles and protects against endotoxin-induced tissue damage. There is also evidence that apo(a) is protective against pathogens. Taken together, the evidence suggests that it might be valuable to introduce the concept that plasma lipoproteins belong in the realm of host immune response.

Plasma lipoproteins are important components of the immune system

Plasma lipoproteins (VLDL, LDL, Lp[a] and HDL) function primarily in lipid transport among tissues and organs. However, cumulative evidence suggests that lipoproteins may also prevent bacterial, viral and parasitic infections and are therefore a component of innate immunity. Lipoproteins can also detoxify lipopolysaccharide and lipoteichoic acid. Infections can induce oxidation of LDL, and oxLDL in turn plays important anti-infective roles and protects against endotoxin-induced tissue damage. There is also evidence that apo(a) is protective against pathogens. Taken together, the evidence suggests that it might be valuable to introduce the concept that plasma lipoproteins belong in the realm of host immune response.

Presence of capsular locus genes in immunochemically identified encapsulated and unencapsulated Streptococcus pneumoniae sputum isolates obtained from elderly patients with acute lower respiratory tract infection

The principal virulence factor of Streptococcus pneumoniae is capsular polysaccharide, and encapsulated pneumococci are more common causes of disease than unencapsulated strains. This study analysed the presence of capsular genes in 59 pneumococcal isolates using two PCR methods targeted at the cpsA and cpsB genes of the capsular biosynthesis locus. The PCR method targeted at the cpsB gene, reported to be essential for encapsulation, was developed in this study. Of 59 pneumococcal isolates, 49 (83 %) were obtained from the sputum samples of elderly patients (≥65 years) with community-acquired pneumonia (CAP) and 10 (17 %) were from those with other acute lower respiratory tract infections (ARIs). Forty (82 %) of the CAP isolates and two (20 %) of the ARI isolates were encapsulated, as assessed by conventional immunochemical methods. Forty-one (98 %) of the 42 encapsulated strains had the cpsB gene present, and in 38 strains the cpsA gene was also detected. One of the unencapsulated isolates gave a positive result for the cpsB gene, and neither of the capsular locus genes were present in all the other unencapsulated strains. The distribution of encapsulated and unencapsulated isolates differed significantly between the two patient groups regardless of whether the presence of capsule was determined immunochemically (P<0.001) or by cpsB PCR (P=0.002). The cpsB PCR developed here was found to be a rapid and reliable method to detect the pneumococcal capsule locus and may have potential in sputum diagnostics when investigating the pneumococcal aetiology of CAP.

Versatility of choline metabolism and choline-binding proteins in Streptococcus pneumoniae and commensal streptococci

The pneumococcal choline-containing teichoic acids are targeted by cholinebinding proteins (CBPs), major surface components implicated in the interaction with host cells and bacterial cell physiology. CBPs also occur in closely related commensal species, Streptococcus oralis and Streptococcus mitis, and many strains of these species contain choline in their cell wall. Physiologically relevant CBPs including cell wall lytic enzymes are highly conserved between Streptococcus pneumoniae and S. mitis. In contrast, the virulence-associated CBPs, CbpA, PspA and PcpA, are S. pneumoniae specific and are thus relevant for the characteristic properties of this species.

Regulation of natural genetic transformation and acquisition of transforming DNA in Streptococcus pneumoniae

The ability of pneumococci to take up naked DNA from the environment and permanently incorporate the DNA into their genome by recombination has been exploited as a valuable research tool for 80 years. From being viewed as a marginal phenomenon, it has become increasingly clear that horizontal gene transfer by natural transformation is a powerful mechanism for generating genetic diversity, and that it has the potential to cause severe problems for future treatment of pneumococcal disease. This process constitutes a highly efficient mechanism for spreading beta-lactam resistance determinants between streptococcal strains and species, and also threatens to undermine the effect of pneumococcal vaccines. Fortunately, great progress has been made during recent decades to elucidate the mechanism behind natural transformation at a molecular level. Increased insight into these matters will be important for future development of therapeutic strategies and countermeasures aimed at reducing the spread of hazardous traits. In this review, we focus on recent developments in our understanding of competence regulation, DNA acquisition and the role of natural transformation in the dissemination of virulence and beta-lactam resistance determinants.

Diagnostic detection of Streptococcus pneumoniae PpmA in urine

Streptococcus pneumoniae infections are often difficult to diagnose accurately, as it is not uncommon for clinical samples to be culture-negative, particularly after antibiotic administration. The rapid Binax NOW S. pneumoniae urinary antigen test lacks specificity in children, owing to pneumococcal antigen reactions in children who are nasopharyngeal carriers of S. pneumoniae. A western blot assay with a specific polyclonal antibody was developed for direct detection of the putative proteinase maturation protein A (PpmA) in urine samples from children with pneumococcal infections. The sensitivity and specificity of the assay were 66.7% and 100%, respectively. Previous antibiotic treatment or S. pneumoniae nasopharyngeal colonization did not affect PpmA antigenuria. Results also demonstrated the presence of PpmA cross-reactive epitopes in commensal bacteria that co-colonize the nasopharyngeal niche, although the non-pneumococcal cross-reactive protein(s) did not interfere with the detection assay. S. pneumoniae PpmA in the urine of children with pneumococcal infections may be a marker that has the potential to be used in the clinical diagnosis of pneumococcal infection.

Evolution of Streptococcus pneumoniae and its close commensal relatives

Streptococcus pneumoniae is a member of the Mitis group of streptococci which, according to 16S rRNA-sequence based phylogenetic reconstruction, includes 12 species. While other species of this group are considered prototypes of commensal bacteria, S. pneumoniae is among the most frequent microbial killers worldwide. Population genetic analysis of 118 strains, supported by demonstration of a distinct cell wall carbohydrate structure and competence pheromone sequence signature, shows that S. pneumoniae is one of several hundred evolutionary lineages forming a cluster separate from Streptococcus oralis and Streptococcus infantis. The remaining lineages of this distinct cluster are commensals previously collectively referred to as Streptococcus mitis and each represent separate species by traditional taxonomic standard. Virulence genes including the operon for capsule polysaccharide synthesis and genes encoding IgA1 protease, pneumolysin, and autolysin were randomly distributed among S. mitis lineages. Estimates of the evolutionary age of the lineages, the identical location of remnants of virulence genes in the genomes of commensal strains, the pattern of genome reductions, and the proportion of unique genes and their origin support the model that the entire cluster of S. pneumoniae, S. pseudopneumoniae, and S. mitis lineages evolved from pneumococcus-like bacteria presumably pathogenic to the common immediate ancestor of hominoids. During their adaptation to a commensal life style, most of the lineages gradually lost the majority of genes determining virulence and became genetically distinct due to sexual isolation in their respective hosts.

Rapid diagnosis of pneumococcal pneumonia among HIV-infected adults with urine antigen detection

OBJECTIVES

Streptococcus pneumoniae is the leading cause of bacterial pneumonia and associated bacteremia during HIV infection. Rapid diagnostic assays may limit inappropriate therapy.

METHODS

Clinical signs and symptoms and sera and urine were collected prospectively from 70 adults with pneumococcal pneumonia, including 47 with HIV co-infection. Pneumococcal C-polysaccharide antigen was detected in urine using the Binax immunochromatographic test (ICT). A systematic review of 24 published studies was conducted.

RESULTS

Clinical symptoms, signs, and laboratory parameters except leukocytosis, were similar in HIV-infected and HIV-seronegative pneumonia. The performance of the urine antigen ICT was independent of HIV-status (sensitivity 81%, specificity 98%, positive (PPV) and negative predictive values (NPV) 98%, and 82%, respectively). The sensitivity of sputum Gram's stain was 58% (34/59) with sputum unable to be provided by 16%. The CRP response was identical in HIV-infected (mean+/-SD) 133+/-88 vs. seronegative 135+/-104 mg/L (p=0.9). In the systematic review, the ICT performance revealed 74% sensitivity (95% CI 72-77%) and 94% specificity (95% CI 93-95%). Urine antigen testing increases etiologic diagnosis by 23% (range: 10-59%) when testing adults with community acquired pneumonia of unknown etiology.

CONCLUSIONS

Urinary antigen detection provides a credible rapid diagnostic test for pneumococcal pneumonia regardless of HIV-status. CRP response to acute infection is similar in HIV co-infection and increases diagnostic certainty.

Performance of a pneumolysin enzyme-linked immunosorbent assay for diagnosis of pneumococcal infections

A pneumolysin-specific enzyme-linked immunosorbent assay (PLY-ELISA) for the detection of pneumolysin in urine was developed and evaluated in comparison with the commercially available Binax Now Streptococcus pneumoniae test (Binax, Portland, ME) for the diagnosis of pneumococcal infections. Assay sensitivity was evaluated using urine from 108 patients with culture-confirmed pneumococcal infections. In adults, the sensitivity and specificity of the PLY-ELISA were 56.6% and 92.2%, respectively. In children with nasopharyngeal pneumococcal carriage, PLY-ELISA and Binax Now S. pneumoniae test sensitivities were 62.5% and 87.5%, respectively, while specificities were 94.4% and 27.8%, respectively. In children with nonnasopharyngeal pneumococcal carriage, PLY-ELISA and Binax Now S. pneumoniae test sensitivities were 68.7% and 93.7%, respectively, and test specificities were 94.1% and 41.2%, respectively. The persistence of pneumolysin in urine of pneumococcal pneumonia patients decreased significantly after 4 to 6 days of treatment. Our data suggest that combining the high specificity of the PLY-ELISA with the high sensitivity of the Binax Now S. pneumoniae test would enable pneumococcal infections to be accurately diagnosed in children.

Report of two cases of aseptic meningitis with persistence of pneumococcal cell wall components in cerebrospinal fluid after Pneumococcal meningitis

We describe two cases of aseptic meningitis occurring some time after pneumococcal meningitis. Both cases may have resulted from an inflammatory response to persistent pneumococcal cell membrane components, as the cerebrospinal fluid samples were positive by the Binax NOW Streptococcus pneumoniae antigen test. Potential mechanisms and diagnostic impact are discussed.

Evaluating the Use of a Streptococcus pneumoniae Urinary Antigen Detection Kit for the Management of Community-Acquired Pneumonia in Japan

BACKGROUND

The urinary antigen detection kit for Streptococcus pneumoniae was tested.

OBJECTIVES

It was our aim to evaluate the usefulness of the immunochromatographic membrane test by doing a large prospective study of community-acquired pneumonia (CAP) in Japan.

METHODS

We prospectively evaluated the use of the S. pneumoniae urinary antigen detection kit and analyzed the treatment and clinical effect seen in patients with positive test kit results. One hundred and fifty-six patients with CAP admitted to our hospital between October 2001 and September 2003 were evaluated.

RESULTS

In 49% of these CAP patients, the causative microorganisms were isolated. S. pneumoniae was suspected to be the causative microorganism in 15%, but positive results of the urinary antigen detection kit indicated S. pneumoniae to be a probable microorganism in 28%, even though antibiotics had previously been administered to half of the patients. The kit was particularly useful for diagnosing patients with poor quality sputum in whom antibiotics treatment nevertheless had to be selected. Antibiotics appropriate for S. pneumoniae (mainly penicillin) were given. The treatment was found to have excellent clinical results in 89% of the CAP patients.

CONCLUSIONS

The S. pneumoniae urinary antigen detection kit was considered to be useful in selecting treatment since there was a high level of clinical effectiveness when the most suitable antibiotics were immediately administered to positive patients. The use of the S. pneumoniae urinary antigen kit is rapid and simple compared with conventional microbiological procedures.

Streptococcus pneumoniae antigen test using positive blood culture bottles as an alternative method to diagnose pneumococcal bacteremia

Recovery of Streptococcus pneumoniae from positive blood culture bottles may be difficult due to autolysis of pneumococci. Therefore, we evaluated the performance of the Binax NOW S. pneumoniae antigen test with samples from positive blood culture bottles and defined the duration of detectable pneumococcal antigen in these bottles. Use of the S. pneumoniae antigen test is an alternative method for identifying S. pneumoniae from positive blood culture bottles and may enable a diagnosis of pneumococcal bacteremia despite negative subcultures.

Induction of immune response toStreptococcus pneumoniaeby administration of oral viridans streptococci via phosphorylcholine determinant

Expression of the phosphorylcholine (PC) epitope was examined in 48 viridans streptococcal strains, including Streptococcus pneumoniae R36a as the positive control, and their immunogenicity to induce an S. pneumoniae-cross-reactive response was evaluated in mice. Thirteen strains were found to express the PC epitope, while no obvious association was found between the taxonomic categories and PC expression. Serum antibody responses to S. pneumoniae cells were induced in mice by intraperitoneal injection of the PC-positive, but not PC-negative, strains. The cross-reactive antibodies induced by non-pneumococcal oral streptococci were readily inhibited by free hapten PC. IgM was the sole isotype of the anti-pneumococcal and anti-PC antibodies, and the phenomenon of immunological memory was not observed. Since the anti-PC antibody is critically important for resistance against pneumococcal infection in mice, the present results indicate the possibility that PC-expressing oral commensal bacteria have a significant influence on the hosts' responsiveness to S. pneumoniae.

A 3-year prospective study of a urinary antigen-detection test for Streptococcus pneumoniae in community-acquired pneumonia: utility and clinical impact on the reported etiology

To evaluate the efficacy of a rapid immunochromatographic membrane test (ICT) for the detection of Streptococcus pneumoniae urinary antigen for diagnosing S. pneumoniae pneumonia, ICT was performed with urine samples using the Binax NOW Streptococcus pneumoniae kit at the time of admission. The results were compared with those from conventional microbiological studies. Three hundred and forty-nine adult patients with CAP who were admitted to the hospital were studied prospectively between February 2001 and January 2004. The ICT test was positive in 115 (33.0%) of 349 patients enrolled into the study and in 63 (75.9%) of 83 patients with pneumococcal pneumonia confirmed by conventional methods. The test revealed a sensitivity of 75.9% and a specificity of 94.0% with conventional microbiological criteria used as the reference standard. The positive predictive value was 91.3%, and the negative predictive value was 82.6%. The clinical features of 53 patients in whom ICT was positive and no pathogen was identified showed no significant difference from those of 83 patients who had pneumococcal pneumonia identified by conventional methods. The diagnostic yield of pneumococcal pneumonia was increased up to 38.9% using ICT combined with conventional methods. The Binax NOW ICT to detect S. pneumoniae urinary antigen is therefore a rapid and useful method for diagnosing pneumococcal pneumonia. Induction of ICT will prove the predominance of S. pneumoniae in the etiology of CAP.

Performance of the Binax NOW Streptococcus pneumoniae urinary antigen assay for diagnosis of pneumonia in children with underlying pulmonary diseases in the absence of acute pneumococcal infection

The performance of the Binax NOW immunochromatographic test for detecting Streptococcus pneumoniae antigen in urine specimens from 103 children presenting underlying pulmonary diseases with no recent pneumococcal infection was assessed. Our data indicate that this assay is unlikely to be useful for discriminating between children with and without pneumococcal pneumonia.

A C-reactive protein mutant that does not bind to phosphocholine and pneumococcal C-polysaccharide

C-reactive protein (CRP), the major human acute-phase plasma protein, binds to phosphocholine (PCh) residues present in pneumococcal C-polysaccharide (PnC) of Streptococcus pneumoniae and to PCh exposed on damaged and apoptotic cells. CRP also binds, in a PCh-inhibitable manner, to ligands that do not contain PCh, such as fibronectin (Fn). Crystallographic data on CRP-PCh complexes indicate that Phe(66) and Glu(81) contribute to the formation of the PCh binding site of CRP. We used site-directed mutagenesis to analyze the contribution of Phe(66) and Glu(81) to the binding of CRP to PCh, and to generate a CRP mutant that does not bind to PCh-containing ligands. Five CRP mutants, F66A, F66Y, E81A, E81K, and F66A/E81A, were constructed, expressed in COS cells, purified, and characterized for their binding to PnC, PCh-BSA, and Fn. Wild-type and F66Y CRP bound to PnC with similar avidities, while binding of E81A and E81K mutants to PnC was substantially reduced. The F66A and F66A/E81A mutants did not bind to PnC. Identical results were obtained with PCh-BSA. In contrast, all five CRP mutants bound to Fn as well as did wild-type CRP. We conclude that Phe(66) is the major determinant of CRP-PCh interaction and is critical for binding of CRP to PnC. The data also suggest that the binding sites for PCh and Fn on CRP are distinct. A CRP mutant incapable of binding to PCh provides a tool to assess PCh-inhibitable interactions of CRP with its other biologically significant ligands, and to further investigate the functions of CRP in host defense and inflammation.

Assessment of the Binax NOW Streptococcus pneumoniae urinary antigen test in children with nasopharyngeal pneumococcal carriage

We evaluated the Binax NOW Streptococcus pneumoniae urinary antigen assay by testing 210 healthy children aged 2--60 months living in urban slums of Quito, Ecuador. Healthy children with nasopharyngeal carriage of S. pneumoniae were significantly more likely to have positive urinary antigen test results than were children who were not carriers (30 of 138 vs. 3 of 71 children; chi2=10.8; P<.001). The rate of nasopharyngeal carriage of S. pneumoniae decreased with increasing age; the lowest rates were found in children with the worst nutritional status.

Rapid killing of Streptococcus pneumoniae with a bacteriophage cell wall hydrolase

Nasopharyngeal carriage is the major reservoir for Streptococcus pneumoniae in the community. Although eliminating this reservoir would greatly reduce disease occurrence, no suitable intervention has been available for this purpose. We show here that seconds after contact, a purified pneumococcal bacteriophage lytic enzyme (Pal) is able to kill 15 common serotypes of pneumococci, including highly penicillin-resistant strains. In vivo, previously colonized mice revealed undetectable pneumococcal titers 5 hours after a single enzyme treatment. Pal enzyme had little or no effect on microorganisms normally found in the human oropharynx, and Pal-resistant pneumococci could not be detected after extensive exposure to the enzyme.

Phosphorylcholine-dependent cross-reactivity between dental plaque bacteria and oxidized low-density lipoproteins

Antibodies reactive with phosphorylcholine (PC) are ubiquitous in human sera, but the antigens stimulating their production and their function are not clear. Previous studies have shown that a significant proportion of dental plaque bacteria contain PC as determined by reactivity with PC-specific mouse myeloma proteins and monoclonal antibodies. Additionally, serum antibody concentrations of immunoglobulin (IgG) G anti-PC are higher in sera of individuals who have experienced periodontal attachment loss than those who are periodontally healthy. These data implicate the oral microflora as a source of antigen-stimulating anti-PC responses. Recent data also indicate that antibodies with specificity for PC are elevated in ApoE-deficient mice, a model for studies of athersclerosis, and that such antibodies bound oxidized low-density lipoproteins (LDL) (oxLDL) in atherosclerotic plaques. These data prompted the hypothesis that human anti-PC could bind to both oral bacteria and human oxLDL, and that these antigens are cross-reactive. We therefore examined the ability of human anti-PC to bind to PC-bearing strains of oral bacteria using enzyme-linked immunosorbent inhibition assays and by assessment of direct binding of affinity-purified human anti-PC to PC-bearing Actinobacillus actinomycetemcomitans. Our results indicated that PC-bearing strains of Streptococcus oralis, Streptococcus sanguis, Haemophilus aphrophilus, Actinomyces naeslundii, Fusobacterium nucleatum, and A. actinomycetemcomitans, as well as a strain of Streptococcus pneumoniae, absorbed up to 80% of anti-PC IgG antibody from human sera. Furthermore, purified anti-PC bound to a PC-bearing strain of A. actinomycetemcomitans but only poorly to a PC-negative strain. OxLDL also absorbed anti-PC from human sera, and oxLDL but not LDL reacted with up to 80% of the anti-PC in human sera. Furthermore, purified anti-PC bound directly to oxLDL but not to LDL. The data indicate that PC-containing antigens on a variety of common oral bacteria are cross-reactive with neoantigens expressed in oxLDL. We propose that PC-bearing dental plaque microorganisms may induce an antibody response to PC that could influence the inflammatory response associated with atherosclerosis.

Detection of Streptococcus pneumoniae antigen by a rapid immunochromatographic assay in urine samples

STUDY OBJECTIVES

Evaluation of a newly available rapid (15 min) immunochromatographic membrane test (ICT) to detect Streptococcus pneumoniae in urine samples, in order to assess its utility in the diagnosis of bacteremic and nonbacteremic pneumococcal pneumonia.

DESIGN

Retrospective study.

SETTING

We studied urine samples from 51 patients with bacteremic and nonbacteremic pneumonia due to S pneumoniae diagnosed by blood culture and pneumococcal polysaccharide capsular antigen detection by counterimmunoelectrophoresis in urine samples, 16 patients with probable pneumococcal pneumonia, 71 patients with nonpneumococcal pneumonia, and 16 patients with pneumonia but no pathogen identified. Urine samples were collected and frozen at - 20 degrees C until used. The ICT test was performed following the instructions of the manufacturer.

MEASUREMENTS AND RESULTS

S. pneumoniae antigen was detected in 41 of 51 patients with pneumococcal pneumonia (80.4%); results were positive in 23 of 28 bacteremic cases (82.1%) and in 18 of 23 nonbacteremic cases (78.3%). From patients with a diagnosis of presumptive pneumococcal pneumonia, antigen was detected in seven urine samples (43.7%) and also in one case of the 16 patients with pneumonia but no pathogen identified. The specificity of the ICT test was 97.2%.

CONCLUSION

The ICT assay is a valuable tool for the diagnosis of pneumococcal pneumonia, especially for the nonbacteremic cases.

Structures of two cell wall-associated polysaccharides of a Streptococcus mitis biovar 1 strain. A unique teichoic acid-like polysaccharide and the group O antigen which is a C-polysaccharide in common with pneumococci

The cell wall of Streptococcus mitis biovar 1 strain SK137 contains the C-polysaccharide known as the common antigen of a closely related species Streptococcus pneumoniae, and a teichoic acid-like polysaccharide with a unique structure. The two polysaccharides are different entities and could be partially separated by gel chromatography. The structures of the two polysaccharides were determined by chemical methods and by NMR spectroscopy. The teichoic acid-like polymer has a heptasaccharide phosphate repeating unit with the following structure: The structure neither contains ribitol nor glycerol phosphate as classical teichoic acids do, thus we have used the expression teichoic acid-like for this polysaccharide. The following structure of the C-polysaccharide repeating unit was established: where AAT is 2-acetamido-4-amino-2,4, 6-trideoxy-D-galactose. It has a carbohydrate backbone identical to that of one of the two structures of C-polysaccharide previously identified in S. pneumoniae. C-polysaccharide of S. mitis is characterized by the presence, in each repeating unit, of two residues of phosphocholine and both galactosamine residues in the N-acetylated form. Immunochemical analysis showed that C-polysaccharide constitutes the Lancefield group O antigen. Studies using mAbs directed against the backbone and against the phosphocholine moiety of the C-polysaccharide revealed several different patterns of these epitopes among 95 S. mitis and Streptococcus oralis strains tested and the exclusive presence of the group O antigen in the majority of S. mitis biovar 1 strains.

Invasion of human vascular endothelial cells by Actinobacillus actinomycetemcomitans via the receptor for platelet-activating factor

Strains of the periodontal pathogen Actinobacillus actinomycetemcomitans are variable with respect to display of phosphorylcholine (PC)-bearing antigens. We have examined strains of A. actinomycetemcomitans with and without PC to assess their ability to invade endothelial cells via the receptor for platelet-activating factor (PAF). Results of antibiotic protection assays indicate that PC-bearing A. actinomycetemcomitans invade human vascular endothelial cells by a mechanism inhibitable by CV3988, a PAF receptor antagonist, and by PAF itself. The invasive phenotype was verified by transmission electron microscopy. A PC-deficient strain of this organism was not invasive. This property, in addition to the established ability of A. actinomycetemcomitans to invade epithelial cells, may provide this organism with access to the systemic circulation. The ability of PC-bearing oral bacteria to access the circulation may also explain the elevated levels of anti-PC antibody in serum found in patients with periodontitis.

Antiphosphorylcholine antibody levels are elevated in humans with periodontal diseases

Human immunoglobulin G2 (IgG2) serum concentrations and the IgG2 antibody response to Actinobacillus actinomycetemcomitans can be influenced by genes, by environmental factors such as smoking, and by periodontal disease status. Examination of the IgG2 response to phosphorylcholine (PC), a response thought to be mainly induced by the C polysaccharide of Streptococcus pneumoniae, suggested that periodontal disease status was also associated with this response. This prompted the hypothesis that PC is an important oral antigen associated with organisms in the periodontal flora and that anti-PC antibody is elevated as a consequence of periodontal disease. Subjects in various periodontal disease diagnostic categories in which attachment loss is exhibited were tested for anti-PC in serum. Those with adult periodontitis, localized juvenile periodontitis, generalized early-onset periodontitis, and gingival recession all had similar levels of anti-PC IgG2 serum antibody which were significantly greater than in the group of subjects with no attachment loss. Analysis of plaque samples from subgingival and supragingival sites in all diseases categories for reactivity with the anti-PC specific monoclonal antibody TEPC-15 revealed that a substantial proportion of the bacteria in dental plaque (30 to 40%) bear PC antigen; this antigen was not restricted to morphotypes resembling only cocci but was also present on rods and branched filamentous organisms. We found that S. mitis, S. oralis, and S. sanguis, as well as oral actinomycetes, including A. viscosus, A. odontolyticus, and A. israelii, incorporated substantial amounts of [(3)H]choline from culture media. Further analysis of antigens derived from these organisms by Western blot indicated that S. oralis, S. sanguis, A. viscosus, A. odontolyticus, and A. israelii contained TEPC-15-reactive antigens. The data show that many commonly occurring bacterial species found in dental plaque contain PC antigen and that immunization with plaque-derived PC antigens as a consequence of inflammation and periodontal attachment loss may influence systemic anti-PC antibody concentrations.

Phosphorylcholine: friend or foe of the immune system?

Phosphorylcholine (PC) is a structural component of a variety of prokaryotic and eukaryotic pathogens. In some cases, PC in infectious agents can benefit the infected host due to its targeting by both the innate and adaptive immune responses. However, as discussed here, PC exhibits a surprising range of immunomodulatory properties that might be to the detriment of the host.

Dominant cross-reactive antibodies generated during the response to a variety of oral bacterial species detect phosphorylcholine

The intraperitoneal immunization of Balb/c mice with subgingival plaque from advanced periodontal pockets or with certain strains of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Actinomyces israelii, Streptococcus mitis, or Streptococcus oralis yielded frequently indistinguishable IgM monoclonal antibodies which were reactive with antigens from a variety of oral bacteria. This study aimed to characterize the specificity of such monoclonal antibodies and the diversity of oral bacteria expressing this target antigen or epitope. Using a competitive enzyme-linked immunosorbent assay to study a variety of competitor substances for their capacity to bind to the monoclonal antibodies, we identified phosphorylcholine as the recognized epitope. The concentration of positive bacteria with extraordinarily bright cell wall fluorescence in indirect immunofluorescence assays varied between 0.1% and 15% in subgingival and from 10 to 40% in supragingival plaque samples. Labeled bacteria belonged to different morphotypes, including cocci, rods, and filaments. Of 75 species tested in vitro, 14 gram-positive and four gram-negative species were found to harbor positive strains. Haemophilus aphrophilus, Streptococcus mitis, Actinomyces georgiae, Actinomyces gerencseriae, Actinomyces israelii, and Actinomyces odontolyticus were human oral species of which all tested strains were capable of binding the cross-reactive monoclonal antibodies. In contrast, Actinomyces naeslundii was consistently negative. These data provide evidence for a much more common expression of phosphorylcholine by oral bacteria than hitherto believed but do not indicate an obvious association of phosphorylcholine expression with oral health or inflammatory periodontal diseases.

Current classification of the oral streptococci

The classification of the oral streptococci has long remained a difficult area of streptococcal taxonomy. This article reviews the current classification of these bacteria into four species groups, and each group is described in detail. The often confusing changes that have taken place in the classification, identification and nomenclature of the member species are reviewed against a historical background of gradually improving techniques and approaches, leading towards a natural classification based primarily on genotypic evidence. Identification schemes currently in use employing biochemical tests are also reviewed, together with alternative molecular approaches.

Detection of the phosphorylcholine epitope in streptococci, Haemophilus and pathogenic Neisseriae by immunoblotting

The phosphorylcholine (PC) determinant in Streptococcus pneumoniae is known to be linked to the cell wall polysaccharides (C-Ps) and to the lipoteichoic acid (LTA) (Forssman antigen) of the plasma membrane. Western blotting with two PC specific murine monoclonal antibodies (MAbs) designated 145,F-2 (IgM) and 147,A-1 (IgA) showed a similar ladder-like pattern for all examined strains of S. pneumoniae and Streptococcus mitis. Purified antigens run in parallel indicated that this ladder pattern is due to the PC of LTA. Unlike other techniques, Western blotting thus enables the identification of only one of the streptococcal structures carrying the PC epitope. Gram-negative organisms were also examined, and six of 11 Haemophilus influenzae strains reacted with the MAbs. For this species, unlike the streptococci, only one fast moving band was detected. Analyses by thin-layer chromatography (TLC) detected the PC epitope in lipopolysaccharide (LPS) fraction from H. influenzae. Some strains of the Neisseriaceae family were also positive by Western blotting, but TLC and immunostaining did not detect the PC determinant in LPS.

Investigation of a choline phosphate synthesis pathway in Streptococcus pneumoniae: evidence for choline phosphate cytidylyltransferase activity

In this study we have demonstrated the activity of a choline phosphate cytidylyltransferase in cell free extracts of Streptococcus pneumoniae. Southern blot analysis of restricted S. pneumoniae genomic DNA probed with the gene coding for the choline phosphate cytidylyltransferase of Saccharomyces cerevisiae demonstrated that there is homology between the S. cerevisiae cct gene and genomic DNA of S. pneumoniae. We believe that this enzyme is involved in the biosynthesis of the choline containing cell wall antigens, teichoic acid and lipoteichoic acid, catalysing the activation of choline phosphate to CDP-choline which is then incorporated into the polysaccharide moiety.