The nonpathogenic commensal Neisseria: friends and foes in infectious disease.

PURPOSE OF REVIEW: Nonpathogenic commensal Neisseria are rarely considered in the clinical setting despite evidence that they can cause invasive opportunistic infections. In contrast, they may offer protection against pathogenic Neisseria, and such relationships are being actively explored in experimental studies. RECENT FINDINGS: Recent case reports are presented of invasive infection caused by nonpathogenic Neisseria in patients on novel biologic therapies. On the other hand, Neisseria lactamica, a nonpathogenic commensal, has been shown in human challenge studies to inhibit colonization by Neisseria meningitidis. Experimental mouse models have also explored the inhibitory effects of nonpathogenic Neisseria on Neisseria gonnhoreae infection. Cutting-edge advances in metagenomics and microbiomics are being used to understand the mechanisms underpinning these effects. SUMMARY: Clinicians should have increased awareness of nonpathogenic Neisseria. First, as new immunomodulating therapies become licenced, the interactions that maintain balance between commensals and their human hosts may be altered. Second, these bacteria are showing promise in their capacity to exclude pathogenic Neisseria species from their anatomical niches.

Kingella kingae infections in children.

BACKGROUND: Improvements in culture techniques and molecular detection methods have led to findings indicating that, particularly in infants and young children, Kingella kingae is a significantly more important pathogen than previously thought. However, despite this, the pediatric community is still largely unaware of the existence of this organism. The aim of this review is therefore to summarise current knowledge of the epidemiology, transmission, clinical presentation, diagnosis and treatment of K. kingae infections in children. DISCUSSION: K. kingae is a common coloniser of the oropharynx, can be transmitted from child to child, and can cause outbreaks of infection. Invasive infections almost exclusively occur in children aged between six months and four years of age, and involve mainly joints and bone, less frequently the endocardium, and very rarely other localisations. With the exception of bacteremia and endocarditis, which can be followed by severe complications, the diseases due to K. kingae are usually accompanied by mild to moderate clinical signs and symptoms, and only slightly altered laboratory data. Moreover, they generally respond to widely used antibiotics, although resistant strains are reported. However, the mild symptoms and limited increase in the levels of acute phase reactants create problems because K. kingae disease may be confused with other clinical conditions that have a similar clinical picture. CONCLUSIONS: Although K. kingae was identified more than 50 years ago, it is poorly known by pediatricians and is not systematically sought in laboratories. Education is therefore necessary in order to reduce the risk of outbreaks, permit the early identification of K. kingae infections, and allow the prompt prescription of adequate therapeutic regimens capable of avoiding the risk of a negative evolution in those cases in which this elusive pathogen can cause significant clinical problems.

Outbreaks of Kingella kingae infections in daycare facilities.

During the past decade, transmission of the bacterium Kingella kingae has caused clusters of serious infections, including osteomyelitis, septic arthritis, bacteremia, endocarditis, and meningitis, among children in daycare centers in the United States, France, and Israel. These events have been characterized by high attack rates of disease and prevalence of the invasive strain among asymptomatic classmates of the respective index patients, suggesting that the causative organisms benefitted from enhanced colonization fitness, high transmissibility, and high virulence. After prophylactic antibacterial drugs were administered to close contacts of infected children, no further cases of disease were detected in the facilities, although test results showed that some children still carried the bacterium. Increased awareness of this public health problem and use of improved culture methods and sensitive nucleic acid amplification assays for detecting infected children and respiratory carriers are needed to identify and adequately investigate outbreaks of K. kingae disease.

How I treat paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal blood disorder that manifests with hemolytic anemia, bone marrow failure, and thrombosis. Many of the clinical manifestations of the disease result from complement-mediated intravascular hemolysis. Allogeneic bone marrow transplantation is the only curative therapy for PNH. Eculizumab, a monoclonal antibody that blocks terminal complement activation, is highly effective in reducing hemolysis, improving quality of life, and reducing the risk for thrombosis in PNH patients. Insights into the relevance of detecting PNH cells in PNH and other bone marrow failure disorders are highlighted, and indications for treating PNH patients with bone marrow transplantation and eculizumab are explored.

A randomized controlled trial for reducing risks for sexually transmitted infections through enhanced patient-based partner notification.

OBJECTIVES: We sought to assess the effectiveness of approaches targeting improved sexually transmitted infection (STI) sexual partner notification through patient referral. METHODS: From January 2002 through December 2004, 600 patients with Neisseria gonorrhoeae or Chlamydia trachomatis were recruited from STI clinics and randomly assigned to either a standard-of-care group or a group that was counseled at the time of diagnosis and given additional follow-up contact. Participants completed an interview at baseline, 1 month, and 6 months and were checked at 6 months for gonorrhea or chlamydial infection via nucleic acid amplification testing of urine. RESULTS: Program participants were more likely to report sexual partner notification at 1 month (86% control, 92% intervention; adjusted odds ratio [AOR] = 1.8; 95% confidence interval [CI] = 1.02, 3.0) and were more likely to report no unprotected sexual intercourse at 6 months (38% control, 48% intervention; AOR = 1.5; 95% CI = 1.1, 2.1). Gonorrhea or chlamydial infection was detected in 6% of intervention and 11% of control participants at follow-up (AOR = 2.2; 95% CI = 1.1, 4.1), with greatest benefits seen among men (for gender interaction, P = .03). CONCLUSIONS: This patient-based sexual partner notification program can help reduce risks for subsequent STIs among urban, minority patients presenting for care at STI clinics.

Update on the management of skin, soft-tissue, and osteoarticular infections in children.

PURPOSE OF REVIEW: To provide an update on the diagnosis and management of skin, soft-tissue, and osteoarticular infections in children. RECENT FINDINGS: Our understanding of the epidemiology of skin and soft-tissue infections and osteoarticular infections is changing rapidly. Community-associated methicillin-resistant Staphylococcus aureus has become a predominant cause of childhood skin and soft-tissue infections. Kingella kingae is also increasingly identified as a cause of osteoarticular infections. Challenges in Staphylococcus aureus treatment and Kingella kingae identification are changing the approach to skin and soft-tissue infections and osteoarticular infections. SUMMARY: Community-associated methicillin-resistant Staphylococcus aureus should be considered a cause of skin and soft-tissue infections. Empiric antimicrobial choices should be modified in areas in which there is a more than 10% prevalence of community-associated methicillin-resistant Staphylococcus aureus infection. Decontamination of shared sports equipment should be undertaken to minimize person-to-person spread. No established guideline for eradication of carriage of community-associated methicillin-resistant Staphylococcus aureus exists. Kingella kingae is a more prevalent cause of osteoarticular infections than previously recognized and can cause outbreaks of invasive infection via person-to-person transmission. Modification of culturing procedures for osteoarticular infections including inoculation of infected joint fluid and bone in blood-culture bottles should be considered.

La inmunización frente a Neisseria meningitidis serogrupo C con vacuna conjugada: siete años de experiencia / Immunization against serogroup C Neisseria meningitidis with conjugated vaccines: seven years' experience

Se expone la trayectoria de la vacuna conjugada antimeningocócica frente a N. meningitidisserogrupo C en los países que la han introducido en sus calendarios, en cuanto a pautasde utilización y al seguimiento de la efectividad clínica. A la vista de la disminución dela efectividad con el tiempo transcurrido desde la recepción de la vacuna, especialmente eninmunizados como lactantes, se comentan las distintas estrategias y pautas de vacunaciónfuturas

Concise review about different immunization schedules with polysaccharide-protein conjugatevaccines against serogroup C N meningitidis in various countries. Regarding some decreasein effectiveness months after its administration, particularly in vaccinated as infants,the author discusses possible schedules in the near future

La enfermedad meningocócica C en España. ¿Es necesario modificar la pauta de vacunación? / Meningococcal C disease in Spain. Is it necessary to change the vaccination schedule?

Se expone la trayectoria de la vacuna conjugada frente a Neisseria meningitidis serogrupo Cen España desde su introducción en el calendario, sus pautas de utilización y el seguimiento desu efectividad clínica. Se comenta la posibilidad de reducir el número de dosis en la pauta deprimovacunación en los lactantes, la conveniencia de una dosis de recuerdo en el segundo añode vida, en vista de la rápida disminución de la efectividad en los que recibieron la vacuna siendolactantes, las posibles actuaciones sobre la población adolescente y algunas estrategias devacunación futuras

Concise review regarding the evolution of the polysaccharide-protein conjugate vaccineagainst serogroup C Neisseria meningitidis since its introduction in the immunization schedulein Spain, its administration guidelines and the follow up of its clinical effectiveness. Theauthor considers the possibility of reducing the number of vaccine doses for infants, the advisabilityof a booster shot in the second year of life, due to its reduced effectiveness in thosevaccinated as infants, possible interventions in the adolescent population and some immunizationschedules for the future

Protein secretion and secreted proteins in pathogenic Neisseriaceae.

Secreted proteins of pathogenic bacteria are often essential virulence factors. They are involved, for example, in the adherence of the bacteria to host cells or required to suppress the host's defence mechanisms. Until recently, only IgA1 protease had been studied in detail in the NeisseriaceaeNeisseria meningitidis and Neisseria gonorrhoeae. The availability of their genome sequences, however, has boosted research in this area. Here, we present a survey of the secretome of the pathogenic Neisseriaceae, based on the available genome sequences, and the current knowledge of the functions and structures of the secreted proteins. Of the six protein-secretion pathways that are widely disseminated among Gram-negative bacteria, three pathways appear to be present among the Neisseriaceae, i.e. the autotransporter-, the two-partner- and the type I-secretion mechanisms. Comparison of the predicted secretomes reveals a considerable flexibility. As compared with N. meningitidis and the nonpathogen N. lactamica, N. gonorrhoeae appears to have a considerably degenerated secretome, which may reflect its altered niche occupancy. The flexibility of the secretome may be enhanced by the presence of ORFs in the genomes potentially encoding fragments of secreted proteins. We hypothesize that these ORFs may substitute for the corresponding fragments in the full-length genes through genetic recombination, thereby changing the host-cell receptor specificity of the secreted protein.

Outbreak of osteomyelitis/septic arthritis caused by Kingella kingae among child care center attendees.

OBJECTIVE: Kingella kingae often colonizes the oropharyngeal and respiratory tracts of children but infrequently causes invasive disease. In mid-October 2003, 2 confirmed and 1 probable case of K kingae osteomyelitis/septic arthritis occurred among children in the same 16- to 24-month-old toddler classroom of a child care center. The objective of this study was to investigate the epidemiology of K kingae colonization and invasive disease among child care attendees. METHODS: Staff at the center were interviewed, and a site visit was performed. Oropharyngeal cultures were obtained from the staff and children aged 0 to 5 years to assess the prevalence of Kingella colonization. Bacterial isolates were subtyped by pulsed-field gel electrophoresis (PFGE), and DNA sequencing of the 16S rRNA gene was performed. A telephone survey inquiring about potential risk factors and the general health of each child was also conducted. All children and staff in the affected toddler classroom were given rifampin prophylaxis and recultured 10 to 14 days later. For epidemiologic and microbiologic comparison, oropharyngeal cultures were obtained from a cohort of children at a control child care center with similar demographics and were analyzed using the same laboratory methods. The main outcome measures were prevalence and risk factors for colonization and invasive disease and comparison of bacterial isolates by molecular subtyping and DNA sequencing. RESULTS: The 2 confirmed case patients required hospitalization, surgical debridement, and intravenous antibiotic therapy. The probable case patient was initially misdiagnosed; MRI 16 days later revealed evidence of ankle osteomyelitis. The site visit revealed no obvious outbreak source. Of 122 children in the center, 115 (94%) were cultured. Fifteen (13%) were colonized with K kingae, with the highest prevalence in the affected toddler classroom (9 [45%] of 20 children; all case patients tested negative but had received antibiotics). Six colonized children were distributed among the older classrooms; 2 were siblings of colonized toddlers. No staff (n = 28) or children aged <16 months were colonized. Isolates from the 2 confirmed case patients and from the colonized children had an indistinguishable PFGE pattern. No risk factors for invasive disease or colonization were identified from the telephone survey. Of the 9 colonized toddlers who took rifampin, 3 (33%) remained positive on reculture; an additional toddler, initially negative, was positive on reculture. The children of the control child care center demonstrated a similar degree and distribution of K kingae colonization; of 118 potential subjects, 45 (38%) underwent oropharyngeal culture, and 7 (16%) were colonized with K kingae. The highest prevalence again occurred in the toddler classrooms. All 7 isolates from the control facility had an indistinguishable PFGE pattern; this pattern differed from the PFGE pattern observed from the outbreak center isolates. 16S rRNA gene sequencing demonstrated that the outbreak K kingae strain exhibited >98% homology to the ATCC-type strain, although several sequence deviations were present. Sequencing of the control center strain demonstrated more homology to the outbreak center strain than to the ATCC-type strain. CONCLUSIONS: This is the first reported outbreak of invasive K kingae disease. The high prevalence in the affected toddler class and the matching PFGE pattern are consistent with child-to-child transmission within the child care center. Rifampin was modestly effective in eliminating carriage. DNA sequence analysis suggests that there may be considerable variability within the species K kingae and that different K kingae strains may demonstrate varying degrees of pathogenicity.

Mucosal vaccination against encapsulated respiratory bacteria--new potentials for conjugate vaccines?

Polysaccharide (PS)-encapsulated bacteria such as Haemophilus influenzae type b (Hib), Streptococcus pneumoniae (pneumococcus), Neisseria meningitides (meningococcus) and group B streptococcus (GBS), cause a major proportion of disease in early childhood. Native PS vaccines are immunogenic and provide protection against disease in healthy adults but do not induce immunological memory. PSs are T-cell-independent antigens and do not elicit antibodies in infants and young children, but by conjugating PS to proteins they become T-cell dependent and immunogenic at an early age. Despite excellent efficacy of PS-protein conjugate vaccines against invasive disease, protection against mucosal infections such as pneumococcal otitis media has been less efficacious. Circulating PS-specific antibodies may protect against infections at mucosal sites, but mucosal immunoglobulin A antibodies may also contribute significantly to protection against mucosal infections. Mucosal immunization of experimental animals with conjugate vaccines against Hib, pneumococcus, meningococcus and GBS induces systemic and mucosal immune responses, which provide protection against carriage, otitis media and invasive disease in a variety of challenge models, providing new means for protection against encapsulated bacteria. In addition, mucosal immunization of neonatal mice with a pneumococcal conjugate and the nontoxic adjuvant LT-K63 has been superior to parenteral immunization in eliciting protective antibodies and PS-specific memory, and thus circumventing the limitations of antibody responses to PS that are responsible for enhanced susceptibility of neonates and infants to infections caused by encapsulated bacteria. Through T-cell dependent enhanced immunogenicity of PS-protein conjugate vaccines, mucosal immunization could be an attractive approach for early life immunization against encapsulated bacteria.

Vaccination and otitis media.

Acute otitis media (AOM) caused by Streptococcus pneumoniae, Haemophilus influenzae or Moraxella catarrhalis may induce specific systemic and/or local immune responses, which may protect from otitis media caused by the same bacteria. However, earlier clinical trials with pneumococcal capsular polysaccharide vaccines have not been successful in preventing AOM. Recently developed pneumococcal polysaccharide-protein conjugates proved immunogenic even in infants, and a heptavalent pneumococcal CRM 197 conjugate vaccine gave a 57% reduction in the number of pneumococcal AOM episodes caused by the vaccine serotypes in infants in Finland. H. influenzae causing AOM is noncapsulated, and like M. catarrhalis, calls for another kind of vaccine development. Suitable vaccine candidates are not yet available but are under development and being tested for immunogenicity and safety. In some trials influenza vaccines have shown protection from AOM during respective viral epidemics. Passive immunoprophylaxis might be an important alternative for immunocompromised children, although this approach has not been successful so far. Mucosal immunization and the advent of DNA and gene technology will open new interesting prospects in the future.

The outer membrane proteins UspA1 and UspA2 of Moraxella catarrhalis are highly conserved in nasopharyngeal isolates from young children.

UspA1 and UspA2 of Moraxella catarrhalis are vaccine candidates. The aims of this study were to determine: (1) the frequencies of occurrence and (2) the degrees of conservation of two surface-exposed epitopes of the uspA1 and uspA2 genes and their respective gene products in 108 nasopharyngeal isolates from young children. The uspA1 and uspA2 genes were detected in 107 (99%) and 108 (100%) isolates, respectively. Twenty-three of 108 uspA2 genes (21%) were identified as the variant gene uspA2H. One-hundred and five isolates (97%) expressed the mAb17C7-reactive epitope shared by UspA1 and UspA2, and 103 isolates (95%) reacted with the UspA1-specific mAb24B5. The only isolate which lacked a uspA1 gene demonstrated reduced adherence to HEp-2 cells and complement sensitivity. The data indicate that both uspA genes and the expression of at least two surface-exposed epitopes are virtually ubiquitous in isolates from a population at risk for otitis media. A vaccine capable of inducing a bactericidal immune response against the mAb17C7- and/or mAb24B5-reactive epitopes appears promising.

Method for reducing endotoxin in Moraxella catarrhalis UspA2 protein preparations.

The UspA2 protein from the bacterium Moraxella catarrhalis is a potential vaccine candidate for preventing human diseases caused by this organism. Before a vaccine can be administered parentally, the level of endotoxin must be reduced as much as possible. However, in this case the endotoxin was very tightly complexed with the UspA2 protein and could not be dissociated with Triton X-100. It was found that it dissociated from the protein with the zwitterionic detergents Zwittergent 3-12 and Zwittergent 3-14. The endotoxin could then be separated from the protein by either ion-exchange or gel filtration chromatography. Using the limulus amoebocyte lysate assay for quantitation, the endotoxin was reduced approximately 20,000-fold. The removal of residual endotoxin from UspA2 preparations had no detrimental effect on the immunological properties of the protein. Mouse antisera raised against UspA2 prior to, and following endotoxin reduction exhibited comparable antibody and bactericidal titers against the tested strains. Further, mice immunized with both preparations, followed by pulmonary challenge with either a homologous or a heterologous isolate, exhibited comparable levels of clearance.

Functional characteristics of a protective monoclonal antibody against serotype A and C lipooligosaccharides from Moraxella catarrhalis.

A monoclonal antibody (MAb), designated MAb 8E7 (immunoglobulin G3), specific for Moraxella catarrhalis lipooligosaccharide (LOS) was evaluated for its functional activity in vitro and in a mouse model of colonization. Enzyme-linked immunosorbent assay (ELISA) demonstrated that the MAb 8E7 could be prepared to a high titer against LOS of the homologous strain 035E, and that it had bactericidal activity. MAb 8E7 reacted with M. catarrhalis serotype A and C LOSs but not serotype B LOS, as measured by ELISA and Western blotting. On the basis of published structures of LOSs, this suggests that the epitope recognized by MAb 8E7 is directed to a common sequence of either alpha-GlcNAc-(1-->2)-beta-Glc-(1--> at the branch substituting position 4 of the trisubstituted Glc residue or a terminal tetrasaccharide alpha-Gal-(1-->4)-beta-Gal-(1-->4)-alpha-Glc-(1-->2)-beta-Glc-(1--> at the branch substituting position 6 of the trisubstituted Glc residue. In a whole-cell ELISA, MAb 8E7 reacted with 70% of the 30 wild-type strains and clinical isolates tested. Immuno-electron microscopy demonstrated that MAb 8E7 reacted with a cell surface-exposed epitope of LOS on strain O35E. MAb 8E7 inhibited the adherence of strain O35E to Chang conjunctival epithelial cells by 90%. Passive immunization with MAb 8E7 could significantly enhance the clearance of strain O35E from mouse lungs in an aerosol challenge mouse model. This enhanced bacterial clearance was inhibited when MAb 8E7 was absorbed by M. catarrhalis serotype A LOS, indicating that the M. catarrhalis LOS-directed antibody may play a major role in the enhancement of M. catarrhalis clearance from lungs. These data suggest that MAb 8E7, which recognizes surface-exposed LOS of M. catarrhalis, is a protective antibody against M. catarrhalis.

Progress toward the development of a vaccine to prevent Moraxella (Branhamella) catarrhalis infections.

Moraxella catarrhalis is a major cause of otitis media and respiratory disease. Vaccine development is at the antigen identification stage. This review examines the more promising antigens, including the 200K protein, the hemagglutinins, the lactoferrin-binding proteins, the UspA proteins, the CopB protein, the transferrin-binding proteins, the CD protein, the E protein and lipooligosaccharide conjugates. Clinical testing of some of these antigens should begin soon.

Vaccines for Moraxella catarrhalis.

Vaccine development for Moraxella catarrhalis is in the antigen identification stage. M. catarrhalis does not appear to synthesize secreted antigens such as exotoxins, nor does it appear to possess a carbohydrate capsule. Modified forms of these antigens are usually good vaccine components. There is some interest in whole bacterial cells and membrane fractions, but the search has largely focused on purified outer surface antigens. All of the present antigens have been selected based on the response seen in animals, although the antibody response seen in people exposed to the bacterium provides some guidance. The antibody response provides information related to the cross-strain preservation of epitopes and whether they are surface exposed. Antigens that elicit antibodies that have complement dependent bactericidal capacity, opsonophagocytic activity or interfere with one of the antigen's known functions such as adhesion or nutrient acquisition are particularly valued. In addition to examining the antibody response, some antigens have been evaluated in a murine pulmonary clearance model. Using these assays and model, several vaccine candidates have been identified. The antigens may be roughly classified by the function they serve the bacterium. One set appears to promote adhesion to host tissues and includes the hemagglutinins, ubiquitous surface protein A1 (UspA1), and possibly the CD protein. A second set is involved in nutrient acquisition. This set includes the lactoferrin binding protein A (LbpA) and lactoferrin binding protein B (LbpB), the transferrin binding protein A (TbpA) and transferrin binding protein B (TbpB), the CD and E porins, and the Catarrhalis outer membrane protein B (CopB). A third set is comprised of antigens involved in virulence and it includes lipooligosaccharide (LOS) and the ubiquitous surface protein A2 (UspA2). Antigens of unknown function, such as the 200K protein, may also be vaccine candidates. The antigens that are most suitable will be determined in clinical studies that are only beginning now.