A Comprehensive Review on the Interplay between Neisseria spp. and Host Sphingolipid Metabolites.

Sphingolipids represent a class of structural related lipids involved in membrane biology and various cellular processes including cell growth, apoptosis, inflammation and migration. Over the past decade, sphingolipids have become the focus of intensive studies regarding their involvement in infectious diseases. Pathogens can manipulate the sphingolipid metabolism resulting in cell membrane reorganization and receptor recruitment to facilitate their entry. They may recruit specific host sphingolipid metabolites to establish a favorable niche for intracellular survival and proliferation. In contrast, some sphingolipid metabolites can also act as a first line defense against bacteria based on their antimicrobial activity. In this review, we will focus on the strategies employed by pathogenic Neisseria spp. to modulate the sphingolipid metabolism and hijack the sphingolipid balance in the host to promote cellular colonization, invasion and intracellular survival. Novel techniques and innovative approaches will be highlighted that allow imaging of sphingolipid derivatives in the host cell as well as in the pathogen.

Biofilm microbiome in extracorporeal membrane oxygenator catheters.

Despite the formation of biofilms on catheters for extracorporeal membrane oxygenation (ECMO), some patients do not show bacteremia. To elucidate the specific linkage between biofilms and bacteremia in patients with ECMO, an improved understanding of the microbial community within catheter biofilms is necessary. Hence, we aimed to evaluate the biofilm microbiome of ECMO catheters from adults with (n = 6) and without (n = 15) bacteremia. The microbiomes of the catheter biofilms were evaluated by profiling the V3 and V4 regions of bacterial 16s rRNA genes using the Illumina MiSeq sequencing platform. In total, 2,548,172 reads, with an average of 121,341 reads per sample, were generated. Although alpha diversity was slightly higher in the non-bacteremic group, the difference was not statistically significant. In addition, there was no difference in beta diversity between the two groups. We found 367 different genera, of which 8 were present in all samples regardless of group; Limnohabitans, Flavobacterium, Delftia, Massilia, Bacillus, Candidatus, Xiphinematobacter, and CL0-1 showed an abundance of more than 1% in the sample. In particular, Arthrobacter, SMB53, Neisseria, Ortrobactrum, Candidatus Rhabdochlamydia, Deefgae, Dyella, Paracoccus, and Pedobacter were highly abundant in the bacteremic group. Network analysis indicated that the microbiome of the bacteremic group was more complex than that of the non-bacteremic group. Flavobacterium and CL0.1, which were abundant in the bacteremic group, were considered important genera because they connected different subnetworks. Biofilm characteristics in ECMO catheters varied according to the presence or absence of bacteremia. There were no significant differences in diversity between the two groups, but there were significant differences in the community composition of the biofilms. The biofilm-associated community was dynamic, with the bacteremic group showing very complex network connections within the microbiome.

Commensal Neisseria Kill Neisseria gonorrhoeae through a DNA-Dependent Mechanism.

The mucosa is colonized with commensal Neisseria. Some of these niches are sites of infection for the STD pathogen Neisseria gonorrhoeae (Ngo). Given the antagonistic behavior of commensal bacteria toward their pathogenic relatives, we hypothesized that commensal Neisseria may negatively affect Ngo colonization. Here, we report that commensal species of Neisseria kill Ngo through a mechanism based on genetic competence and DNA methylation state. Specifically, commensal-triggered killing occurs when the pathogen takes up commensal DNA containing a methylation pattern that it does not recognize. Indeed, any DNA will kill Ngo if it can enter the cell, is differentially methylated, and has homology to the pathogen genome. Consistent with these findings, commensal Neisseria elongata accelerates Ngo clearance from the mouse in a DNA-uptake-dependent manner. Collectively, we propose that commensal Neisseria antagonizes Ngo infection through a DNA-mediated mechanism and that DNA is a potential microbicide against this highly drug-resistant pathogen.

Location, Location, Location-Commensalism, Damage and Evolution of the Pathogenic Neisseria.

The 10 human-restricted Neisseria species all colonize mucosal surfaces, but show a spectrum of pathogenicity. The commensal Neisseria do not normally cause pathology, while the two pathogenic species, Neisseria meningitidis and Neisseria gonorrhoeae, straddle the border between commensalism and pathogenicity. Why the pathogenic Neisseria continue to mediate host damage after thousands of years of co-evolution with their human host, and why the commensal species have not acquired the ability to damage the host, if this capability provides a selective advantage, is not understood. One way the pathogenic species are different from the commensal species is by their ability to induce PMN inflammation, which is dependent on the site of colonization. I discuss how the site of colonization dictates whether copious inflammation occurs with both pathogenic species. I put forth a model that posits that an ancestor of both pathogenic species changed colonization site from the oral cavity to the genital tract of a human or humanoid and had to evolve multiple, new traits - to induce PMN inflammation and avoid adaptive immunity - to allow efficient sexual transmission. This model predicts that PMN inflammation produces the serious sequelae of gonorrhea and increases the probability that N. meningitidis might exit the oral cavity to produce systemic disease. In both cases, the pathology produced by these host-adapted species is an unintended by product of the inflammation but host damage does not provide any selective advantage for these organisms.

Lipopolysaccharides From Non-Helicobacter pylori Gastric Bacteria Potently Stimulate Interleukin-8 Production in Gastric Epithelial Cells.

BACKGROUND: Gastric acid secretion is compromised in chronic Helicobacter pylori (H. pylori) infection allowing overgrowth of non-H. pylori gastric bacteria (NHGB) in the stomach. METHODS: NHGB were isolated from gastric mucosa in selective media and further characterized with biochemical methods and 16S rRNA gene sequencing. Human gastric tissues were studied with indirect immunofluorescence with antibodies against H. pylori and Neisseria subflava (N. subflava). Gastric epithelial cell lines were cocultured with bacteria or incubated with lipopolysaccharides isolated from NHGB, and interleukin-8 released in the media was measured by enzyme-linked immunosorbent assay. Expression of Toll-like receptor (TLR)2, TLR4, it's coreceptor myeloid differentiation factor 2 (MD2), and CD14 in gastric cells was investigated by immunofluorescence microscopy and reverse transcriptase-polymerase chain reaction. RESULTS: Haemophilus species, Neisseria species, Fusobacterium species, and Veillonella species were predominant Gram-negative bacteria coinfected with H. pylori. Lipopolysaccharides from N. subflava potently stimulated interleukin-8 secretion in MKN45 cells which was cancelled by preincubation with polymyxin B. TLR2, TLR4, CD14, and myeloid differentiation factor 2 were expressed in MKN45 cells, though their levels of expression were low. N. subflava adhered to MKN45 cells in vitro and colocalized with H. pylori in the human gastric mucosa. CONCLUSIONS: Our data suggest that N. subflava colonized in the gastric mucosa contribute to gastric inflammation during chronic H. pylori gastritis. TRANSLATIONAL IMPACT: NHGB may perpetuate gastric inflammation and accelerate neoplastic progression in the hypochlorhydric stomach.

Infant anemia is associated with reduced TLR-stimulated cytokine responses and increased nasopharyngeal colonization with Moxarella catarrhalis.

Anemia is a major public health problem in young children. Reports on the role of anemia on infectious diseases remained controversial. We aim to investigate the effect of anemia on innate immunity, nasopharyngeal bacterial colonization, and subsequent infectious outcome. Blood tests were examined at the age of 12 months. TLR-induced cytokine production was assessed by ELISA. Bacteria from nasopharyngeal specimens were identified with traditional culture. Clinical infectious diseases were followed yearly until 3 years of age. Result showed that of the 423 infants, 72 had hemoglobin level ≤ 11 g/dL, among which 55% had normal iron level. There was significant association between hemoglobin level and TLR1-2, and 4 induced IL-6 (p = 0.04, 0.02) and that of TLR4 stimulated TNF-α response (p = 0.04). Children with anemia had higher nasopharyngeal colonization with Moxarella catarrhalis. Clinical analysis did not show anemia to be associated with infectious morbidity. However, children who developed LRTIs had mean lower ferritin levels. We speculated that iron might be the key factor related to infectious morbidity. Thus, to investigate the role of anemia in infectious diseases, it is important to first consider the prevalence of iron deficit, since the incidence of iron deficiency-induced anemia may vary among different regions.

Neisseria models of infection and persistence in the upper respiratory tract.

The Gram-negative bacteria genus Neisseria includes both pathogenic and commensal species that are found primarily in the upper respiratory tract of humans and animals. The development of animal models to study neisserial pathogenesis has focused almost exclusively on two species that cause disease in humans. These include Neisseria meningitidis, an obligate commensal that can cause invasive disease, and N. gonorrhoeae, the causative agent of gonorrhea. Both pathogens can persist in the upper respiratory tract. This article will give a brief overview of the genus Neisseria. The anatomy of the upper respiratory tract and its use as a niche for bacteria will be discussed. Next, studies that provide insight about the first stage of upper respiratory tract infection, namely colonization, will be reviewed. Most studies of upper respiratory tract infection have focused on N. meningitidis infections of laboratory mice. This review will also discuss models of respiratory tract persistence by Neisseria species, including commensals, in mice, non-human primates and human volunteers. The article includes a section that discusses the future utility of upper respiratory tract models in informing the development of effective antimicrobial therapies. Such knowledge is needed to minimize the dissemination of antimicrobial resistance from respiratory reservoirs.

Fatal Neisseria macacae infective endocarditis: first report.

INTRODUCTION: Neisseria macacae is a Gram-negative diplococcus, found in the oropharynx of healthy Rhesus Monkeys. Infections caused by N. macacae in humans are extremely rare. CASE PRESENTATION: We present here the first case of N. macacae infective endocarditis in a 65-year-old man with a native aortic valve infection complicated by a peri-aortic abscess. N. macacae was isolated from blood culture and was found on the cardiac valve using 16S rDNA detection. Despite an appropriate antibiotic therapy, and aortic homograft replacement, and mitral repair, the patient died 4 days after surgery from a massive hemorrhagic stroke.

Uncovering oral Neisseria tropism and persistence using metagenomic sequencing.

Microbial epidemiology and population genomics have previously been carried out near-exclusively for organisms grown in vitro. Metagenomics helps to overcome this limitation, but it is still challenging to achieve strain-level characterization of microorganisms from culture-independent data with sufficient resolution for epidemiological modelling. Here, we have developed multiple complementary approaches that can be combined to profile and track individual microbial strains. To specifically profile highly recombinant neisseriae from oral metagenomes, we integrated four metagenomic analysis techniques: single nucleotide polymorphisms in the clade's core genome, DNA uptake sequence signatures, metagenomic multilocus sequence typing and strain-specific marker genes. We applied these tools to 520 oral metagenomes from the Human Microbiome Project, finding evidence of site tropism and temporal intra-subject strain retention. Although the opportunistic pathogen Neisseria meningitidis is enriched for colonization in the throat, N. flavescens and N. subflava populate the tongue dorsum, and N. sicca, N. mucosa and N. elongata the gingival plaque. The buccal mucosa appeared as an intermediate ecological niche between the plaque and the tongue. The resulting approaches to metagenomic strain profiling are generalizable and can be extended to other organisms and microbiomes across environments.

A bit of a mouthful.

This month's Genome Watch explores recent advances in the identification of species-level and strain-level diversity in microbiome studies, and highlights how these have provided insights into the tropism and persistence of Neisseria spp. in the human oral cavity.

How clonal are Neisseria species? The epidemic clonality model revisited.

The three species Neisseria meningitidis, Neisseria gonorrheae, and Neisseria lactamica are often regarded as highly recombining bacteria. N. meningitidis has been considered a paradigmatic case of the "semiclonal model" or of "epidemic clonality," demonstrating occasional bouts of clonal propagation in an otherwise recombining species. In this model, occasional clonality generates linkage disequilibrium in the short term. In the long run, however, the effects of clonality are countered by recombination. We show that many data are at odds with this proposal and that N. meningitidis fits the criteria that we have proposed for predominant clonal evolution (PCE). We point out that (i) the proposed way to distinguish epidemic clonality from PCE may be faulty and (ii) the evidence of deep phylogenies by microarrays and whole-genome sequencing is at odds with the predictions of the semiclonal model. Last, we revisit the species status of N. meningitidis, N. gonorrheae, and N. lactamica in the light of the PCE model.

Non-pathogenic Neisseria: members of an abundant, multi-habitat, diverse genus.

The genus Neisseria contains the important pathogens Neisseria meningitidis and Neisseria gonorrhoeae. These Gram-negative coccoid bacteria are generally thought to be restricted to humans and inhabit mucosal surfaces in the upper respiratory and genito-urinary tracts. While the meningococcus and gonococcus have been widely studied, far less attention has been paid to other Neisseria species. Here we review current knowledge of the distribution of commensal Neisseria in humans and other hosts. Analysis of the microbiome has revealed that Neisseria is an abundant member of the oropharyngeal flora, and we review its potential impact on health and disease. Neisseria also exhibit remarkable diversity, exhibiting both coccoid and rod-shaped morphologies, as well as environmental strains which are capable of degrading complex organic molecules.

How to get (a)round: mechanisms controlling growth and division of coccoid bacteria.

Bacteria come in a range of shapes, including round, rod-shaped, curved and spiral cells. This morphological diversity implies that different mechanisms exist to guide proper cell growth, division and chromosome segregation. Although the majority of studies on cell division have focused on rod-shaped cells, the development of new genetic and cell biology tools has provided mechanistic insight into the cell cycles of bacteria with different shapes, allowing us to appreciate the underlying molecular basis for their morphological diversity. In this Review, we discuss recent progress that has advanced our knowledge of the complex mechanisms for chromosome segregation and cell division in bacteria which have, deceptively, the simplest possible shape: the cocci.

Effects of high hydrostatic pressure on bacterial growth on human ossicles explanted from cholesteatoma patients.

BACKGROUND: High hydrostatic pressure (HHP) treatment can eliminate cholesteatoma cells from explanted human ossicles prior to re-insertion. We analyzed the effects of HHP treatment on the microbial flora on ossicles and on the planktonic and biofilm states of selected isolates. METHODOLOGY: Twenty-six ossicles were explanted from cholesteatoma patients. Five ossicles were directly analyzed for microbial growth without further treatment. Fifteen ossicles were cut into two pieces. One piece was exposed to HHP of 350 MPa for 10 minutes. Both the treated and untreated (control) pieces were then assessed semi-quantitatively. Three ossicles were cut into two pieces and exposed to identical pressure conditions with or without the addition of one of two different combinations of antibiotics to the medium. Differential effects of 10-minute in vitro exposure of planktonic and biofilm bacteria to pressures of 100 MPa, 250 MPa, 400 MPa and 540 MPa in isotonic and hypotonic media were analyzed using two patient isolates of Staphylococcus epidermidis and Neisseria subflava. Bacterial cell inactivation and biofilm destruction were assessed by colony counting and electron microscopy. PRINCIPAL FINDINGS: A variety of microorganisms were isolated from the ossicles. Irrespective of the medium, HHP treatment at 350 MPa for 10 minutes led to satisfying but incomplete inactivation especially of gram-negative bacteria. The addition of antibiotics increased the efficacy of elimination. A comparison of HHP treatment of planktonic and biofilm cells showed that the effects of HPP were reduced by about one decadic logarithmic unit when HPP was applied to biofilms. High hydrostatic pressure conditions that are suitable to inactivate cholesteatoma cells fail to completely sterilize ossicles even if antibiotics are added. As a result of the reduced microbial load and the viability loss of surviving bacteria, however, there is a lower risk of re-infection after re-insertion.

Techniques to measure pilus retraction forces.

The importance of physical forces in biology is becoming more appreciated. Neisseria gonorrhoeaehas become a paradigm for the study of physical forces in the bacterial world. Cycles of elongations and retractions of Type IV pili enables N. gonorrhoeaebacteria to exert forces on its environment, forces that play major roles in the life cycle of this pathogen. In order to better understand the role of these forces, there is a need to fully characterize them. Here, we present two different techniques, optical tweezers and Polyacrylamide MicroPillars (PoMPs), for measuring pilus retraction forces. Initially designed for N. gonorrhoeae, these assays can be readily modified to study other pilus-bearing bacteria including Neisseria meningitidis.

[Clinical observation of teacher tablets in treatment of pharyngitis].

OBJECTIVE: To evaluate the efficacy of teacher tablets in the treatment of pharyngitis. METHOD: One hundred and thirty six patients with acute pharyngitis or chronic pharyngitis in attack were randamly divided into two groups: treated group (n=68), the patients were given teacher tablets for 7 days, control group (n=68), the patients were given Qinlian capsule for 7 days. Before and after the experimental medicine-taking test, general condition, clinical symptoms and features of examinations on laryngo-pharynx, throat swab bacterial culture were measured. RESULT: After 7 day medicine-taking experiment, teacher tablets can improve clinical symptoms (at an efficacy rate of more than 60%) and features (at an efficacy rate of more than 80%) of laryngopharynx, in treated group, the inhibition ratios of alpha streptococcus, neisseria and staphylococcus aureus are more than 50%. There are no significant difference between treated group and control groups in those detected index. CONCLUSION: Teacher tablets is effective for pharyagitis.

TRAIL limits excessive host immune responses in bacterial meningitis.

Apart from potential roles in anti-tumor surveillance, the TNF-related apoptosis-inducing ligand (TRAIL) has important regulatory functions in the host immune response. We studied antiinflammatory effects of endogenous and recombinant TRAIL (rTRAIL) in experimental meningitis. Following intrathecal application of pneumococcal cell wall, a TLR2 ligand, we found prolonged inflammation, augmented clinical impairment, and increased apoptosis in the hippocampus of TRAIL(-/-) mice. Administration of rTRAIL into the subarachnoid space of TRAIL(-/-) mice or reconstitution of hematopoiesis with wild-type bone marrow cells reversed these effects, suggesting an autoregulatory role of TRAIL within the infiltrating leukocyte population. Importantly, intrathecal application of rTRAIL in wild-type mice with meningitis also decreased inflammation and apoptosis. Moreover, patients suffering from bacterial meningitis showed increased intrathecal synthesis of TRAIL. Our findings provide what we believe is the first evidence that TRAIL may act as a negative regulator of acute CNS inflammation. The ability of TRAIL to modify inflammatory responses and to reduce neuronal cell death in meningitis suggests that it may be used as a novel antiinflammatory agent in invasive infections.

Variations in gene organization and DNA uptake signal sequence in the folP region between commensal and pathogenic Neisseria species.

BACKGROUND: Horizontal gene transfer is an important source of genetic variation among Neisseria species and has contributed to the spread of resistance to penicillin and sulfonamide drugs in the pathogen Neisseria meningitidis. Sulfonamide resistance in Neisseria meningitidis is mediated by altered chromosomal folP genes. At least some folP alleles conferring resistance have been horizontally acquired from other species, presumably from commensal Neisseriae. In this work, the DNA sequence surrounding folP in commensal Neisseria species was determined and compared to corresponding regions in pathogenic Neisseriae, in order to elucidate the potential for inter-species DNA transfer within this region. RESULTS: The upstream region of folP displayed differences in gene order between species, including an insertion of a complete Correia element in Neisseria lactamica and an inversion of a larger genomic segment in Neisseria sicca, Neisseria subflava and Neisseria mucosa. The latter species also had DNA uptake signal sequences (DUS) in this region that were one base different from the DUS in pathogenic Neisseriae. Another interesting finding was evidence of a horizontal transfer event from Neisseria lactamica or Neisseria cinerea that introduced a novel folP allele to the meningococcal population. CONCLUSION: Genetic recombination events immediately upstream of folP and horizontal transfer have resulted in sequence differences in the folP region between the Neisseria species. This variability could be a consequence of the selective pressure on this region exerted by the use of sulfonamide drugs.

Neisseria bacilliformis sp. nov. isolated from human infections.

Most Neisseria species are gram-negative cocci or diplococci; currently, N. elongata is the only species of human origin with a bacillary morphology. Here, we report isolation and characterization of eight strains of another bacillary Neisseria species from human infections. The organisms caused or contributed to either oral cavity-related or respiratory tract infections, and two strains were isolated from blood cultures. The 16S rRNA gene sequences of these organisms, being homogenous or nearly so (99.4 to 100% identity), matched at <96% known Neisseria species and formed a distinct group within the genus. Analysis of the cellular fatty acids showed broad similarity with a few Neisseria species. The organisms were gram negative and measured 0.6 mum by 1.3 to 3.0 mum. They grew well on chocolate agar and on sheep blood agar but did not grow on modified Thayer-Martin agar. They were positive for oxidase and negative for indole production. There was no acid production from dextrose, lactose, maltose, or sucrose. The tests for catalase reaction, nitrate reduction, and tributilin varied with the strains. These results suggest that these organisms represent a novel species within the genus Neisseria, for which the name Neisseria bacilliformis sp. nov. is proposed. The type strain is MDA2833 = ATCC BAA-1200(T) = CCUG50858(T). Distinction between N. bacilliformis and N. elongata can be made confidently by 16S rRNA gene sequencing or cellular fatty acid profiling but may be difficult by morphology or routine biochemical tests.

Contacting the host: insights and implications of pathogenic Neisseria cell interactions.

Neisseria is a highly adapted human specific pathogen that initiates infection at the mucosal epithelia by using multiple adhesins to interact with host cell receptors. Colonization begins at the apical cell surface with a multi-step adhesion cascade, followed by invasion and persistence within the cell and finally transcytosis at the basolateral surface. The type IV pill are implicated in mediating the initial attachment of both meningococci and gonococci, and this association has been shown to involve contact with the cellular receptor CD46. In this review we describe the initial events in the adhesion, invasion and signaling of pathogenic Neisseria focusing on the initial attachment and signaling induced by the interaction of the type IV pili with CD46.