Gonococcal infection: a model of molecular pathogenesis

Irreversible neurological manifestations in undiagnosed disseminated gonococcal infection

Neisseria gonorrhoeae causes a common sexually transmitted infection with manifestations ranging from asymptomatic to urethritis and pelvic inflammatory disease to disseminated infections including septic arthritis. Serious complications may arise in unrecognised or inappropriately treated infections.We report a young, healthy woman who developed fever and joint pain and was diagnosed with an inflammatory arthritis. After starting immune suppressing treatments, she experienced right wrist drop and progressive muscle atrophy, joint contractures and sensory loss. Electrodiagnostic studies showed patchy, mixed neurogenic and myopathic features. Areas of muscle oedema on extremity MRI led to a right brachioradialis biopsy, which showed only nonspecific changes. Other testing, including lumbar puncture and MRI of the brain/spine was noncontributory. Additional history revealed unprotected intercourse with a new partner prior to symptom onset. Urine gonorrhoeae PCR was positive, and right shoulder arthrocentesis confirmed septic arthritis. After intravenous antibiotic treatment with ceftriaxone, she demonstrated slow, incomplete symptomatic improvement.

Increase in gonococcal arthritis in Madrid, Spain, 2022-2023

In recent years, there has been an increase in Neisseria gonorrhoeae infections in Europe and Spain. Disseminated gonococcal infection is an uncommon clinical presentation that includes gonococcal arthritis. Improved antibiotic treatment has reduced the incidence of gonococcal arthritis. However, the increase in gonococcal infections may have increased the frequency of this clinical entity in recent times. We report five cases of gonococcal arthritis in patients in a tertiary-care hospital in the northern area of Madrid (Spain) from October 2022 to October 2023. Major cases occurred in male patients with unprotected sex and polyarticular symptoms requiring hospital admission and treatment with ceftriaxone and cefixime. The use of molecular techniques has allowed the detection of a greater number of culture-negative cases of gonococcal arthritis, as well as the detection of mutations associated with resistance to fluoroquinolone for switching to oral treatment.

Disseminated gonococcal disease in pediatrics: Case report and review of the literature

Hematogenous spread of Neisseria gonorrhoeae, a sexually transmitted pathogen, results in disseminated gonococcal disease (DGD), also known as arthritis-dermatitis syndrome, due to the development of skin lesions, tenosynovitis, and arthritis. The most frequently affected population is young adults. We describe the case of an adolescent female who acutely developed skin lesions, arthritis, tenosynovitis, and constitutional symptoms. The causal agent was identified by a culture of vaginal secretion and treated with ceftriaxone for 7 days with complete recovery. It is important to differentiate this clinical picture from other types of arthritis developed in adolescence.

Mechanisms of host manipulation by Neisseria gonorrhoeae

Neisseria gonorrhoeae (also known as gonococcus) has been causing gonorrhoea in humans since ancient Egyptian times. Today, global gonorrhoea infections are rising at an alarming rate, in concert with an increasing number of antimicrobial-resistant strains. The gonococcus has concurrently evolved several intricate mechanisms that promote pathogenesis by evading both host immunity and defeating common therapeutic interventions. Central to these adaptations is the ability of the gonococcus to manipulate various host microenvironments upon infection. For example, the gonococcus can survive within neutrophils through direct regulation of both the oxidative burst response and maturation of the phagosome; a concerning trait given the important role neutrophils have in defending against invading pathogens. Hence, a detailed understanding of how N. gonorrhoeae exploits the human host to establish and maintain infection is crucial for combating this pathogen. This review summarizes the mechanisms behind host manipulation, with a central focus on the exploitation of host epithelial cell signaling to promote colonization and invasion of the epithelial lining, the modulation of the host immune response to evade both innate and adaptive defenses, and the manipulation of host cell death pathways to both assist colonization and combat antimicrobial activities of innate immune cells. Collectively, these pathways act in concert to enable N. gonorrhoeae to colonize and invade a wide array of host tissues, both establishing and disseminating gonococcal infection.

Neisseria gonorrhoeae arthritis in a patient with systemic lupus: resistance and virulence profiles

In this study, we describe a case report of gonococcal arthritis in a Systemic Lupus Erythematosus patient. Although several mechanisms favor disseminated gonococcal infection (DGI) in patients immunosuppressed by SLE, this association is rarely reported in literature. We performed whole genome sequencing (WGS) of the etiologic agent involved and molecular analysis using a global collection of Neisseria gonorrhoeae strains. Ours is the only sample derived from synovial fluid identified in this collection, the others being from the usual anatomical sites. Antimicrobial susceptibility was determined by disk diffusion and Etest, and WGS was conducted to determine multilocus sequence typing profiles, group isolates based on core genome single nucleotide polymorphisms (SNP), and identify virulence genes and antimicrobial resistance determinants. The N. gonorrhoeae samples in the global collection were highly heterogeneous. The SNP tree had a total 19,532 SNPs in 320 samples. Our sample displayed resistance to ciprofloxacin (MIC = 2 μg/mL) and tetracycline (zone diameter = 0 mm) belonged to ST 1588 and was not closely related to any isolate in the global collection of N. gonorrhoeae strains. The isolate had genetic features related to beta-lactam, tetracycline and quinolone resistance. Seventy-one virulence genes were identified in our sample, belonging to the following classes: adherence, efflux pump, immune modulator, invasion, iron uptake, protease and stress adaptation. Moreover, no virulence genes for immune evasion and toxin were identified.

Right hip gonococcal septic arthritis treatment with successful transition to oral fluoroquinolone

We present a case of gonococcal septic arthritis of the right hip diagnosed via synovial fluid cultures. Antimicrobial susceptibility testing of the synovial fluid demonstrated susceptibility to tetracycline, ciprofloxacin, cefixime and ceftriaxone. Our patient was initially treated with ceftriaxone and was successfully de-escalated to oral levofloxacin to complete the treatment. This case is interesting given the rarity of disseminated gonococcal infections in the 21st century and that most clinical isolates of Neisseria gonorrhoeae are increasingly resistant to fluoroquinolones.

Neisseria gonorrhoeae: DNA Repair Systems and Their Role in Pathogenesis

Neisseria gonorrhoeae (a Gram-negative diplococcus) is a human pathogen and causative agent of gonorrhea, a sexually transmitted infection. The bacterium uses various approaches for adapting to environmental conditions and multiplying efficiently in the human body, such as regulation of expression of gene expression of surface proteins and lipooligosaccharides (e.g., expression of various forms of pilin). The systems of DNA repair play an important role in the bacterium ability to survive in the host body. This review describes DNA repair systems of N. gonorrhoeae and their role in the pathogenicity of this bacterium. A special attention is paid to the mismatch repair system (MMR) and functioning of the MutS and MutL proteins, as well as to the role of these proteins in regulation of the pilin antigenic variation of the N. gonorrhoeae pathogen.

The Anti-Infectious Role of Sphingosine in Microbial Diseases

Sphingolipids are important structural membrane components and, together with cholesterol, are often organized in lipid rafts, where they act as signaling molecules in many cellular functions. They play crucial roles in regulating pathobiological processes, such as cancer, inflammation, and infectious diseases. The bioactive metabolites ceramide, sphingosine-1-phosphate, and sphingosine have been shown to be involved in the pathogenesis of several microbes. In contrast to ceramide, which often promotes bacterial and viral infections (for instance, by mediating adhesion and internalization), sphingosine, which is released from ceramide by the activity of ceramidases, kills many bacterial, viral, and fungal pathogens. In particular, sphingosine is an important natural component of the defense against bacterial pathogens in the respiratory tract. Pathologically reduced sphingosine levels in cystic fibrosis airway epithelial cells are normalized by inhalation of sphingosine, and coating plastic implants with sphingosine prevents bacterial infections. Pretreatment of cells with exogenous sphingosine also prevents the viral spike protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from interacting with host cell receptors and inhibits the propagation of herpes simplex virus type 1 (HSV-1) in macrophages. Recent examinations reveal that the bactericidal effect of sphingosine might be due to bacterial membrane permeabilization and the subsequent death of the bacteria.

Disseminated gonococcal infection in a Japanese man with complement 7 deficiency with compound heterozygous variants: A case report

RATIONALE

Complement deficiency are known to be predisposed to disseminated gonococcal infection (DGI). We herein present a case of DGI involving a Japanese man who latently had a complement 7 deficiency with compound heterozygous variants.

PATIENT CONCERNS

A previously healthy 51-year-old Japanese man complained of sudden-onset high fever. Physical examination revealed various skin lesions including red papules on his trunk and extremities, an impetigo-like pustule on left forearm, and tendinitis of his right forefinger.

DIAGNOSIS

Blood culture testing detected gram-negative cocci, which was confirmed to be Neisseria gonorrhoeae based on mass spectrometry and a pathogen-specific PCR test.

INTERVENTIONS

Screening tests for underlying immunocompromised factors uncovered that complement activities (CH50) was undetectable. With a suspicion of a congenital complement deficiency, genetic analysis revealed rare single nucleotide variants in complement 7 (C7), including c.281-1G>T and a novel variant c.1454C>T (p.A485V). CH50 was normally recovered by adding purified human C7 to the patient's serum, supporting that the patient has C7 deficiency with compound heterozygous variants.

OUTCOMES

Under a diagnosis of DGI, the patient underwent an antibiotic treatment with cefotaxime for a week and was discharged without any sequela.

LESSONS

DGI is a rare sexually-transmitted infection that potentially induces systemic complications. Complement immunity usually defeats N. gonorrhoeae and prevents the organism from causing DGI. This case highlighted the importance of suspecting a complement deficiency when a person develops DGI.

Inhibition of TLR2/TLR4 alleviates the Neisseria gonorrhoeae infection damage in human endometrial epithelial cells via Nrf2 and NF-Kβsignaling

BACKGROUND

Neisseria gonorrhoeae (N.g) is Gram-negative bacteria and can lead to endometritis in female. Toll-like receptors regulate immune response in various diseases. However, the roles of TLR2 and TLR4 in. Neisseria gonorrhoeae-induced infection damage in human endometrial epithelia were investigated.

METHODS

hEECs were infected with N.g (MOI 10 and 100) and cell viability and apoptosis were measured by CCK8 and flow cytometry assays in both infected groups with the uninfected normal hEECs as negative control. TLR2/TLR4 proteins were measured by ELISA method. Pro-inflammatory markers NLRP3, PGES (PGE2) and TNF-α were assessed by RT-qPCR (mRNA expression) and Elisa (protein concentrations). Transfection assays were performed to up- or down- regulate expression of TLR2 and TLR4 so as to study the functions of TLR2/TLR4 in. N.g-infected hEECs, followed by apoptosis and inflammation assessment. Similarly, we explored the interactions between TLR2/TLR4 and Nrf2/NF-κB/p65 by knocking down TLR2/TLR4 to detect the signaling and further regulating the signaling to evaluate TLR2/ TLR4, apoptosis and inflammation in cells.

RESULTS

N.g suppressed cell viabilities and induced cell apoptosis and inflammation. TLR2/TLR4 downregulation inhibited the infection damage. Nrf2 was activated while NF-κB/p65 was depleted as TLR2/ TLR4 was knocked down. Activation of Nrf2 and inhibition of NF-κB resulted in decrease of TLR2/TLR4, which could retard apoptosis and inflammation induced by N.g infection.

CONCLUSION

TLR2/TLR4 depletion could alleviate the N.g-infected hEECs via Nrf2/NF-kB signaling, suggesting that TLR2/TLR4 inhibitors might serve as a treatment to reduce N.g infection in human endometrial epithelia.

Gonococcal osteomyelitis in a pediatric patient with disseminated gonococcal infection: Implications for antimicrobial management

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Cases of gonococcal osteomyelitis are rare but potentially debilitating, with little consensus on risk factors or treatment.

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We present a case of septic arthritis complicated by gonococcal osteomyelitis in an adolescent.

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Prolonged treatment relative to gonococcal arthritis might be needed for ideal outcomes in secondary osteomyelitis.

We report a case of a female teenager with gonococcal septic arthritis of the right shoulder that also caused osteomyelitis of the humeral head. Infection with Neisseria gonorrhoeae is a frequently diagnosed sexually transmitted infection in the sexually active teenage population and disseminated gonococcal infection (DGI) is the most common systemic manifestation of acute gonorrhea. DGI commonly involves acute arthritis, tenosynovitis and dermatitis with less common complications of endocarditis, hepatitis and meningitis. In contrast, osteomyelitis has only rarely been reported as a result of gonococcal infection. Clinicians need to be aware of this unusual manifestation of DGI as a prolonged duration of antimicrobial treatment may be needed to assure complete resolution of this infection.

Epithelial Haven and Autophagy Breakout in Gonococci Infection

The World Health Organization (WHO) has estimated that in 2016, there were 87 million new cases of gonorrhea. Gonorrhea is caused by the sexually transmitted human-exclusive agent Neisseria gonorrhoeae, a Gram-negative diplococcus that causes cervicitis in females and urethritis in males and may lead to more severe complications. Currently, there is no vaccine against N. gonorrhoeae. Its resistance to antibiotics has been increasing in the past few years, reducing the range of treatment options. N. gonorrhoeae requires a surface protein/receptor (Opa proteins, porin, Type IV pili, LOS) to adhere to and invade epithelial cells. During invasion and transcytosis, N. gonorrhoeae is targeted by the autophagy pathway, a cellular maintenance process which balances sources of energy at critical times by degrading damaged organelles and macromolecules in the lysosome. Autophagy is an important host defense mechanism which targets invading pathogens. Based on transmission electron microscopy (TEM) analysis, the intracellular bacteria occupy the autophagosome, a double-membraned vesicle that is formed around molecules or microorganisms during macroautophagy and fuses with lysosomes for degradation. Most of the gonococci end up in autolysosomes for degradation, but a subpopulation of the intracellular bacteria inhibits the maturation of the autophagosome and its fusion with lysosomes by activating mTORC1 (a known suppressor of the autophagy signaling), thus escaping autophagic elimination. This mini review focuses on the cellular features of N. gonorrhoeae during epithelial cell invasion, with a particular focus on how N. gonorrhoeae evades the autophagy pathway.

Intimate Relations: Molecular and Immunologic Interactions Between Neisseria gonorrhoeae and HIV-1

While the global incidence of human immunodeficiency virus (HIV-1) remains well above UNAIDS targets, sexual transmission HIV is surprisingly inefficient. A variety of host, viral and environmental factors can either increase HIV-1 shedding in the infected partner and/or increase mucosal susceptibility of the HIV-1 uninfected partner. Clinical and epidemiological studies have clearly established that Neisseria gonorrhoeae substantially enhances HIV-1 transmission, despite it not being an ulcerative infection. This review will consider findings from molecular, immunologic and clinical studies that have focused on each of these two human-restricted pathogens, in order to develop an integrative model that describes how gonococci can both increase mucosal shedding of HIV-1 from a co-infected person and facilitate virus establishment in a susceptible host.

A Role of Sphingosine in the Intracellular Survival of Neisseria gonorrhoeae

Obligate human pathogenic Neisseria gonorrhoeae are the second most frequent bacterial cause of sexually transmitted diseases. These bacteria invade different mucosal tissues and occasionally disseminate into the bloodstream. Invasion into epithelial cells requires the activation of host cell receptors by the formation of ceramide-rich platforms. Here, we investigated the role of sphingosine in the invasion and intracellular survival of gonococci. Sphingosine exhibited an anti-gonococcal activity in vitro. We used specific sphingosine analogs and click chemistry to visualize sphingosine in infected cells. Sphingosine localized to the membrane of intracellular gonococci. Inhibitor studies and the application of a sphingosine derivative indicated that increased sphingosine levels reduced the intracellular survival of gonococci. We demonstrate here, that sphingosine can target intracellular bacteria and may therefore exert a direct bactericidal effect inside cells.

Biological feasibility and importance of a gonorrhea vaccine for global public health

There is a growing public health interest in controlling sexually transmitted infections (STIs) through vaccination due to increasing recognition of the global disease burden of STIs and the role of STIs in women's reproductive health, adverse pregnancy outcomes, and the health and well-being of neonates. Neisseria gonorrhoeae has historically challenged vaccine development through the expression of phase and antigenically variable surface molecules and its capacity to cause repeated infections without inducing protective immunity. An estimated 78 million new N. gonorrhoeae infections occur annually and the greatest disease burden is carried by low- and middle-income countries (LMIC). Current control measures are clearly inadequate and threatened by the rapid emergence of antibiotic resistance. The gonococcus now holds the status of "super-bug" as there is currently no single reliable monotherapy for empirical treatment of gonorrhea. The problem of antibiotic resistance has elevated treatment costs and necessitated the establishment of large surveillance programs to track the spread of resistant strains. Here we review the need for a gonorrhea vaccine with respect to global disease burden and related socioeconomic and treatment costs, with an emphasis on the impact of gonorrhea on women and newborns. We also highlight the challenge of estimating the impact of a gonorrhea vaccine due to the need for more data on the burden of gonococcal pelvic inflammatory disease and related sequelae and of gonorrhea-associated adverse pregnancy outcomes and the problem of empirical diagnosis and treatment of STIs in LMIC. There is also a lack of clinical and basic science research in the area of gonococcal/chlamydia coinfection, which occurs in a high percentage of individuals with gonorrhea and should be considered when testing the efficacy of gonorrhea vaccines. Finally, we review recent research that suggests a gonorrhea vaccine is feasible and discuss challenges and research gaps in gonorrhea vaccine development.

Successful treatment of gonococcal osteomyelitis with one week of intravenous antibiotic therapy

Gonorrhea is one of the most common sexually transmitted infections (STIs). In a minority of cases, a disseminated infection can occur including gonococcal osteoarticular disease. With the steep and sustained increase in STIs in the US, we could see invasive gonococcal disease more often. Most cases of gonococcal osteomyelitis receive prolonged courses of antibiotic therapy. We report here the successful treatment of gonococcal osteomyelitis with one week of antibiotic therapy. Given the emergence of bacterial resistance worldwide and associated side effects, it is crucial to limit antibiotic exposures to the smallest effective dose possible.

The challenge of converting Gram-positive-only compounds into broad-spectrum antibiotics

Multidrug resistant Gram-negative bacterial infections are on the rise, and there is a lack of new classes of drugs to treat these pathogens. This drug shortage is largely due to the challenge of finding antibiotics that can permeate and persist inside Gram-negative species. Efforts to understand the molecular properties that enable certain compounds to accumulate in Gram-negative bacteria based on retrospective studies of known antibiotics have not been generally actionable in the development of new antibiotics. A recent assessment of the ability of >180 diverse small molecules to accumulate in Escherichia coli led to predictive guidelines for compound accumulation in E. coli. These "eNTRy rules" state that compounds are most likely to accumulate if they contain a nonsterically encumbered ionizable Nitrogen (primary amines are the best), have low Three-dimensionality (globularity ≤ 0.25), and are relatively Rigid (rotatable bonds ≤ 5). In this review, we look back through 50+ years of antibacterial research and 1000s of derivatives and assess this historical data set through the lens of these predictive guidelines. The results are consistent with the eNTRy rules, suggesting that the eNTRy rules may provide an actionable and general roadmap for the conversion of Gram-positive-only compounds into broad-spectrum antibiotics.

Gonorrhea - an evolving disease of the new millennium

Etiology, transmission and protection: Neisseria gonorrhoeae (the gonococcus) is the etiological agent for the strictly human sexually transmitted disease gonorrhea. Infections lead to limited immunity, therefore individuals can become repeatedly infected. Pathology/symptomatology: Gonorrhea is generally a non-complicated mucosal infection with a pustular discharge. More severe sequellae include salpingitis and pelvic inflammatory disease which may lead to sterility and/or ectopic pregnancy. Occasionally, the organism can disseminate as a bloodstream infection. Epidemiology, incidence and prevalence: Gonorrhea is a global disease infecting approximately 60 million people annually. In the United States there are approximately 300, 000 cases each year, with an incidence of approximately 100 cases per 100,000 population. Treatment and curability: Gonorrhea is susceptible to an array of antibiotics. Antibiotic resistance is becoming a major problem and there are fears that the gonococcus will become the next "superbug" as the antibiotic arsenal diminishes. Currently, third generation extended-spectrum cephalosporins are being prescribed. Molecular mechanisms of infection: Gonococci elaborate numerous strategies to thwart the immune system. The organism engages in extensive phase (on/off switching) and antigenic variation of several surface antigens. The organism expresses IgA protease which cleaves mucosal antibody. The organism can become serum resistant due to its ability to sialylate lipooligosaccharide in conjunction with its ability to subvert complement activation. The gonococcus can survive within neutrophils as well as in several other lymphocytic cells. The organism manipulates the immune response such that no immune memory is generated which leads to a lack of protective immunity.

Gonococcal endocarditis: an ever-present threat

The incidence of severe complications of the Neisseria gonorrhoeae infection has presented variations over recent decades since the advent of penicillin. Gonococcal endocarditis (GE) still remains an ever-present threat afflicting the society’s poor and sexually active young population. This entity frequently requires surgical intervention and usually exhibits a poor outcome. The interval between the onset of symptoms and the diagnosis does not usually exceed 4 weeks. One of the characteristics of GE is a proclivity for aortic valve involvement with large vegetation and valve ring abscess formation. The authors report the case of a young man with a 2-week history of fever, malaise, weakness, and progressive heart failure symptoms, who had no previous history of genital complaints or cardiopathy. The physical examination was consistent with acute aortic insufficiency, which was most probably of an infectious origin. The echocardiogram showed thickened aortic cusps and valve insufficiency. After hospital admission, the patient’s clinical status worsened rapidly and he died on the second day. The autopsy findings disclosed aortic valve destruction with vegetation and a ring abscess besides signs of septic shock, such as diffuse alveolar damage, acute tubular necrosis, and zone 3 hepatocellular necrosis. The blood culture isolated N. gonorrhoeae resistant to penicillin and ciprofloxacin. The authors call attention to the pathogen of this particular infectious endocarditis, and the need for early diagnosis and evaluation by a cardiac surgery team.

Isolation of Cell Envelopes and Naturally Released Membrane Vesicles of Neisseria gonorrhoeae

Neisseria gonorrhoeae (GC) is a strict human pathogen and the agent of the sexually transmitted disease gonorrhea. Gonococcal infections have been successfully treated with antibiotics; however, GC has repeatedly developed resistance to each new antibiotic used. Currently, third-generation cephalosporins are recommended, and resistance to these antimicrobials is emerging worldwide. Additionally, no vaccine is available to prevent GC infections. With the dire possibility of untreatable gonorrhea, there is a critical need to identify new therapeutic targets. Cell envelope and membrane vesicle proteins are key factors in pathogenesis, antibiotic resistance, biofilm formation, and general bacterial fitness. Here we describe methods for isolation and purification of GC cell envelopes and spontaneously released membrane vesicles. The isolated proteome fractions can be used in multiple downstream applications, including gel-based and gel-free quantitative proteomics, studies focused on subcellular localization of proteins, transmission electron microscopy, or strain characterization. Presented methods may be easily adapted to other bacterial species.

Quantitative proteomics of the Neisseria gonorrhoeae cell envelope and membrane vesicles for the discovery of potential therapeutic targets

Neisseria gonorrhoeae (GC) is a human-specific pathogen, and the agent of a sexually transmitted disease, gonorrhea. There is a critical need for new approaches to study and treat GC infections because of the growing threat of multidrug-resistant isolates and the lack of a vaccine. Despite the implied role of the GC cell envelope and membrane vesicles in colonization and infection of human tissues and cell lines, comprehensive studies have not been undertaken to elucidate their constituents. Accordingly, in pursuit of novel molecular therapeutic targets, we have applied isobaric tagging for absolute quantification coupled with liquid chromatography and mass spectrometry for proteome quantitative analyses. Mining the proteome of cell envelopes and native membrane vesicles revealed 533 and 168 common proteins, respectively, in analyzed GC strains FA1090, F62, MS11, and 1291. A total of 22 differentially abundant proteins were discovered including previously unknown proteins. Among those proteins that displayed similar abundance in four GC strains, 34 were found in both cell envelopes and membrane vesicles fractions. Focusing on one of them, a homolog of an outer membrane protein LptD, we demonstrated that its depletion caused loss of GC viability. In addition, we selected for initial characterization six predicted outer membrane proteins with unknown function, which were identified as ubiquitous in the cell envelopes derived from examined GC isolates. These studies entitled a construction of deletion mutants and analyses of their resistance to different chemical probes. Loss of NGO1985, in particular, resulted in dramatically decreased GC viability upon treatment with detergents, polymyxin B, and chloramphenicol, suggesting that this protein functions in the maintenance of the cell envelope permeability barrier. Together, these findings underscore the concept that the cell envelope and membrane vesicles contain crucial, yet under-explored determinants of GC physiology, which may represent promising targets for designing new therapeutic interventions.

Vaccines against gonorrhea: current status and future challenges

Gonorrhea occurs at high incidence throughout the world and significantly impacts reproductive health and the spread of human immunodeficiency virus. Current control measures are inadequate and seriously threatened by the rapid emergence of antibiotic resistance. Progress on gonorrhea vaccines has been slow; however, recent advances justify significant effort in this area. Conserved vaccine antigens have been identified that elicit bactericidal antibodies and, or play key roles in pathogenesis that could be targeted by a vaccine-induced response. A murine genital tract infection model is available for systematic testing of antigens, immunization routes and adjuvants, and transgenic mice exist to relieve some host restrictions. Furthermore, mechanisms by which Neisseria gonorrhoeae avoids inducing a protective adaptive response are being elucidated using human cells and the mouse model. Induction of a Th1 response in mice clears infection and induces a memory response, which suggests Th1-inducing adjuvants may be key in vaccine-induced protection. Continued research in this area should include human testing and clinical studies to confirm or negate findings from experimental systems and to define protective host factors.

The biology of Neisseria adhesins

Members of the genus Neisseria include pathogens causing important human diseases such as meningitis, septicaemia, gonorrhoea and pelvic inflammatory disease syndrome. Neisseriae are found on the exposed epithelia of the upper respiratory tract and the urogenital tract. Colonisation of these exposed epithelia is dependent on a repertoire of diverse bacterial molecules, extending not only from the surface of the bacteria but also found within the outer membrane. During invasive disease, pathogenic Neisseriae also interact with immune effector cells, vascular endothelia and the meninges. Neisseria adhesion involves the interplay of these multiple surface factors and in this review we discuss the structure and function of these important molecules and the nature of the host cell receptors and mechanisms involved in their recognition. We also describe the current status for recently identified Neisseria adhesins. Understanding the biology of Neisseria adhesins has an impact not only on the development of new vaccines but also in revealing fundamental knowledge about human biology.

Pilus phase variation switches gonococcal adherence to invasion by caveolin-1-dependent host cell signaling

Many pathogenic bacteria cause local infections but occasionally invade into the blood stream, often with fatal outcome. Very little is known about the mechanism underlying the switch from local to invasive infection. In the case of Neisseria gonorrhoeae, phase variable type 4 pili (T4P) stabilize local infection by mediating microcolony formation and inducing anti-invasive signals. Outer membrane porin PorB(IA), in contrast, is associated with disseminated infection and facilitates the efficient invasion of gonococci into host cells. Here we demonstrate that loss of pili by natural pilus phase variation is a prerequisite for the transition from local to invasive infection. Unexpectedly, both T4P-mediated inhibition of invasion and PorB(IA)-triggered invasion utilize membrane rafts and signaling pathways that depend on caveolin-1-Y14 phosphorylation (Cav1-pY14). We identified p85 regulatory subunit of PI3 kinase (PI3K) and phospholipase Cγ1 as new, exclusive and essential interaction partners for Cav1-pY14 in the course of PorBIA-induced invasion. Active PI3K induces the uptake of gonococci via a new invasion pathway involving protein kinase D1. Our data describe a novel route of bacterial entry into epithelial cells and offer the first mechanistic insight into the switch from local to invasive gonococcal infection.

Structure and function of the PorB porin from disseminating Neisseria gonorrhoeae

The outer membrane of Gram-negative bacteria contains a large number of channel-forming proteins, porins, for the uptake of small nutrient molecules. Neisseria gonorrhoeae PorBIA (PorB of serotype A) are associated with disseminating diseases and mediate a rapid bacterial invasion into host cells in a phosphate-sensitive manner. To gain insights into this structure-function relationship we analysed PorBIA by X-ray crystallography in the presence of phosphate and ATP. The structure of PorBIA in the complex solved at a resolution of 3.3 Å (1 Å=0.1 nm) displays a surplus of positive charges inside the channel. ATP ligand-binding in the channel is co-ordinated by the positively charged residues of the channel interior. These residues ligate the aromatic, sugar and pyrophosphate moieties of the ligand. Two phosphate ions were observed in the structure, one of which clamped by two arginine residues (Arg92 and Arg124) localized at the extraplasmic channel exit. A short β-bulge in β2-strand together with the long L3 loop narrow the barrel diameter significantly and further support substrate specificity through hydrogen bond interactions. Interestingly the structure also comprised a small peptide as a remnant of a periplasmic protein which physically links porin molecules to the peptidoglycan network. To test the importance of Arg92 on bacterial invasion the residue was mutated. In vivo assays of bacteria carrying a R92S mutation confirmed the importance of this residue for host-cell invasion. Furthermore systematic sequence and structure comparisons of PorBIA from Neisseriaceae indicated Arg92 to be unique in disseminating N. gonorrhoeae thereby possibly distinguishing invasion-promoting porins from other neisserial porins.

Fur-mediated global regulatory circuits in pathogenic Neisseria species

The ferric uptake regulator (Fur) protein has been shown to function as a repressor of transcription in a number of diverse microorganisms. However, recent studies have established that Fur can function at a global level as both an activator and a repressor of transcription through both direct and indirect mechanisms. Fur-mediated indirect activation occurs via the repression of additional repressor proteins, or small regulatory RNAs, thereby activating transcription of a previously silent gene. Fur mediates direct activation through binding of Fur to the promoter regions of genes. Whereas the repressive mechanism of Fur has been thoroughly investigated, emerging studies on direct and indirect Fur-mediated activation mechanisms have revealed novel global regulatory circuits.

Combined hormonal contraception may be protective against Neisseria gonorrhoeae infection

BACKGROUND

The role of hormonal contraception on acquisition of gonorrhea has not been well-characterized, as the transmission dynamics of Neisseria gonorrhoeae are poorly understood. The purpose of this study is to determine the influence of hormonal contraception on gonococcal infection in women exposed to males with gonococcal urethritis.

METHODS

Females aged 15 to 35 years reporting sexual contact to a male partner diagnosed with N. gonorrhoeae were enrolled. Demographic and sexual histories, physical findings, and laboratory tests were collected. Women testing positive and negative for cervical N. gonorrhoeae were compared using chi and Fisher exact tests, with multivariable logistic regression performed on those factors independently associated with gonococcal infection on univariate analysis.

RESULTS

N. gonorrhoeae infection occurred in 68 of 107 (64%) women. Women using combined hormonal contraception were significantly less likely than nonusers to test positive for N. gonorrhoeae (32% vs. 76%; prevalence ratio: 0.42; 95% confidence interval: 0.22, 0.78; P = 0.006). Gonorrhea was also less common in depomedroxyprogesterone acetate users. A new sexual partner was also associated with testing positive for gonorrhea (35% vs. 13%; prevalence ratio: 1.47; 95% confidence interval: 1.13, 1.90; P = 0.004).

CONCLUSIONS

Women using combined hormonal contraceptives or depomedroxyprogesterone acetate were less likely to test positive for N. gonorrhoeae after sexual exposure compared with nonusers. Our data suggest that, in addition to contraceptive benefits, modern hormonal contraception may have a protective effect on the acquisition of N. gonorrhoeae.

An unusual case of gonococcal arthritis of the finger

Gonococcal arthritis is the most common acute septic arthritis in sexually active young adults. It is caused by the gram-negative diplococcus Neisseria gonorrhoeae. In 0.5-3% an untreated mucosal infection disseminates throughout the system and affects mostly big joints like the knee, elbows, and ankles. N. gonorrhoeae is a fragile microorganism which is difficult to culture. Penicillin resistance has developed worldwide in recent years, therefore, patients should be treated by a third generation Cephalosporin. In this article, we describe the unexpected finding of septic arthritis in the proximal interphalangeal joint of a 50-year-old patient. The septic arthritis was caused by N. gonorrhoeae.

Low-phosphate-dependent invasion resembles a general way for Neisseria gonorrhoeae to enter host cells

Obligate human-pathogenic Neisseria gonorrhoeae expresses numerous variant surface proteins mediating adherence to and invasion of target cells. The invariant major outer membrane porin PorB of serotype A (P.IA) gonococci triggers invasion into Chang cells only if the medium is devoid of phosphate. Since gonococci expressing PorB(IA) are frequently isolated from patients with severe disseminating infections, the interaction initiated by the porin may be of major relevance for the development of this serious disease. Here, we investigated the low-phosphate-dependent invasion and compared it to the well-known pathways of entry initiated by Opa proteins. P.IA-triggered invasion requires clathrin-coated pit formation and the action of actin and Rho GTPases. However, in contrast to Opa-initiated invasion via heparan sulfate proteoglycans, microtubules, acidic sphingomyelinase, phosphatidylinositol 3-kinase, and myosin light chain kinase are not involved in this entry pathway. Nor are Src kinases required, as they are in invasion, e.g., via the CEACAM3 receptor. Invasion by PorB(IA) occurs in a wide spectrum of cell types, such as primary human epithelial and endothelial cells and in cancer cells of human and animal origin. Low-phosphate-dependent invasion is thus a pathway of gonococcal entry distinct from Opa-mediated invasion.

Identification of the iron-responsive genes of Neisseria gonorrhoeae by microarray analysis in defined medium

To ensure survival, most bacteria must acquire iron, a resource that is sequestered by mammalian hosts. Pathogenic bacteria have therefore evolved intricate systems to sense iron limitation and regulate gene expression appropriately. We used a pan-Neisseria microarray to examine genes regulated in Neisseria gonorrhoeae in response to iron availability in defined medium. Overall, 203 genes varied in expression, 109 up-regulated and 94 down-regulated by iron deprivation. In iron-replete medium, genes essential to rapid bacterial growth were preferentially expressed, while iron transport functions, and predominantly genes of unknown function, were expressed in low-iron medium. Of those TonB-dependent proteins encoded in the FA1090 genome with unknown ligand specificity, expression of three was not controlled by iron availability, suggesting that these receptors may not be high-affinity transporters for iron-containing ligands. Approximately 30% of the operons regulated by iron appeared to be directly under control of Fur. Our data suggest a regulatory cascade where Fur indirectly controls gene expression by affecting the transcription of three secondary regulators. Our data also suggest that a second MerR-like regulator may be directly responding to iron availability and controlling transcription independent of the Fur protein. Comparison of our data with those recently published for Neisseria meningitidis revealed that only a small portion of genes were found to be similarly regulated in these closely related pathogens, while a large number of genes derepressed during iron starvation were unique to each organism.

Acute septic arthritis

Acute septic arthritis may develop as a result of hematogenous seeding, direct introduction, or extension from a contiguous focus of infection. The pathogenesis of acute septic arthritis is multifactorial and depends on the interaction of the host immune response and the adherence factors, toxins, and immunoavoidance strategies of the invading pathogen. Neisseria gonorrhoeae and Staphylococcus aureus are used in discussing the host-pathogen interaction in the pathogenesis of acute septic arthritis. While diagnosis rests on isolation of the bacterial species from synovial fluid samples, patient history, clinical presentation, laboratory findings, and imaging studies are also important. Acute nongonococcal septic arthritis is a medical emergency that can lead to significant morbidity and mortality. Therefore, prompt recognition, rapid and aggressive antimicrobial therapy, and surgical treatment are critical to ensuring a good prognosis. Even with prompt diagnosis and treatment, high mortality and morbidity rates still occur. In contrast, gonococcal arthritis is often successfully treated with antimicrobial therapy alone and demonstrates a very low rate of complications and an excellent prognosis for full return of normal joint function. In the case of prosthetic joint infections, the hardware must be eventually removed by a two-stage revision in order to cure the infection.

The pilus-induced Ca2+ flux triggers lysosome exocytosis and increases the amount of Lamp1 accessible to Neisseria IgA1 protease

The IgA1 protease secreted by the pathogenic Neisseriae cleaves Lamp1, a major integral membrane glycoprotein of lysosomes, and significantly reduces its steady-state levels in an infected cell. IgA1 protease hydrolysis of Lamp1 is inefficient at the low pH of lysosomes, strongly suggesting that the enzyme is unlikely to reduce Lamp1 levels within lysosomes to any appreciable extent. We therefore explored the possibility that the protease may reach Lamp1 through an alternative route. We demonstrate that Neisseria pili induce a transient increase in the levels of cytosolic free Ca2+ in A431 human epithelial cells, as demonstrated previously for ME180 cells. This Ca2+ flux triggers lysosome exocytosis, quickly altering the cellular distribution of Lamp1 and increasing surface Lamp1 levels. Finally, we demonstrate that surface Lamp1 is cleaved by IgA1 protease secreted by adherent bacteria. We conclude that the pilus-induced Ca2+ flux increases the amount of Lamp1 that is cleavable by the IgA1 protease.

[Gonorrhea]

Gonorrhea is a common bacterial infection caused by Neisseria gonorrhoeae, a Gram-negative diplococcus that is transmitted almost exclusively by sexual contact or perinatally. It primarily affects the mucous membranes of the lower genital tract and less frequently those of the rectum, oropharynx, and conjunctivae. Ascending genital infection in women leads to the predominant complication, acute salpingitis, one of the most common causes of female infertility in the world. Since the 1990s, a remarkable surge of information ensued regarding the pathogenesis of gonorrhea and its agent. Gonorrhea has proven difficult to control in most populations and remains a prime example of the influence that social, behavioral, and demographic factors can have on the epidemiology of an infectious disease. The management of gonorrhea and other sexually transmitted infections requires both treatment of the patient as an individual and of his or her sexual partner(s) as a public health measure to interrupt the onward spread of infection and prevent long-term complications.

Charged tmRNA but not tmRNA-mediated proteolysis is essential for Neisseria gonorrhoeae viability

tmRNA, through its tRNA and mRNA properties, adds short peptide tags to abnormal proteins, targeting these proteins for proteolytic degradation. Although the conservation of tmRNA throughout the bacterial kingdom suggests that it must provide a strong selective advantage, it has not been shown to be essential for any bacterium. We report that tmRNA is essential in Neisseria gonorrhoeae. Although tagging per se appears to be required for gonococcal viability, tagging for proteolysis does not. This suggests that the essential roles of tmRNA in N.gonorrhoeae may include resolving stalled translation complexes and/or preventing depletion of free ribosomes. Although derivatives of N.gonorrhoeae expressing Escherichia coli tmRNA as their sole tmRNA were isolated, they appear to form colonies only after acquiring an extragenic suppressor(s).

The type 4 fimbrial subunit gene of pasteurella multocida

Colonisation of host tissue by Gram- negative bacteria is facilitated by various adhesins, one of which is type 4 fimbriae (pili). These structures have been associated with pathogenesis in several bacterial species, and have been shown to mediate colonisation of epithelial surfaces. Recently, type 4 fimbriae were identified and characterised from P. multocida strains A, B and D. The type 4 fimbrial subunit protein (PtfA) was identified as an 18-kDa protein which was isolated from whole membrane fractions. We report here the isolation and characterisation of the gene (ptfA) encoding the PtfA protein from P. multocida VP161 (serotype A:1). Part of the gene was cloned on a 2-kb genomic DNA fragment. The complete ptfA gene was obtained using inverse PCR. The gene and its flanking regions were characterised, and the deduced PtfA amino acid sequence was compared to type 4 subunit protein sequences from other bacterial species. The ptfA gene was amplified and sequenced from several P. multocida strains. Comparison of these sequences revealed variation within the type 4 subunit gene of P. multocida.

Bacterial and protozoal infections

The oral cavity is a common site for manifestations of systemic microbial diseases. Oral lesions may be typical of those seen elsewhere on the body, or the lesions may be modified by the local environment. The ease of examination within the oral cavity, however, and any site-specific features facilitates diagnosis of the systemic condition.

Incorporation of bacterial membrane proteins into liposomes: factors influencing protein reconstitution

Meningococcal and gonococcal outer membrane proteins were reconstituted into liposomes using detergent-mediated dialysis. The detergents octyl glucopyranoside (OGP), sodium cholate and Empigen BB were compared with respect to efficiency of detergent removal and protein incorporation. The rate of OGP removal was greater than for cholate during dialysis. Isopycnic density gradient centrifugation studies showed that liposomes were not formed and hence no protein incorporation occurred during dialysis from an Empigen BB containing reconstitution mixture. Cholate-mediated reconstitution yielded proteoliposomes with only 75% of the protein associated with the vesicles whereas all of the protein was reconstituted into the lipid bilayer during OGP-mediated reconstitution. Essentially complete protein incorporation was achieved with an initial protein-to-lipid ratio of 0.01:1 (w/w) in the reconstitution mixture; however, at higher initial protein-to-lipid ratios (0.02:1) only 75% protein incorporation was achieved. Reconstituted proteoliposomes were observed as large (>300 nm), multilamellar structures using cryo-electron microscopy. Size reduction of these proteoliposomes by extrusion did not result in significant loss of protein or lipid. Extruded proteoliposomes were unilamellar vesicles with mean diameter of about 100 nm.

Assessment, investigation, and management of acute monoarthritis

Trauma is the commonest cause of acute monoarticular joint pain and swelling in patients attending an accident and emergency (A&E) department. However, in a significant minority of patients there will be no history of trauma and consequently a different approach to assessment and investigation is required. Our aim is to offer an outline of how to assess, investigate, and manage a patient with monoarthritis. Despite advances in antibiotic treatment diagnostic delay partly explains why septic arthritis is still associated with considerable morbidity and mortality. It is therefore imperative that joint infection is considered above all other diagnoses. Arthrocentesis is a relatively safe procedure and doctors in A&E medicine are encouraged to develop the skills required to aspirate large joints. In the same way that the A&E department is often portrayed as the shop window of a hospital, the joint can reflect a wide variety of internal diseases. Connective tissue disease, inflammatory bowel disease, sarcoidosis, and vasculitis can all present with a monoarthritis. A non-specific reactive monoarthritis may be a feature of a wide variety of common and uncommon infections including, brucellosis, Lyme disease, and leptospirosis. Drugs are also associated with acute arthritis either through their metabolic consequences or as idiosyncratic drug reactions. The ability for the joint to reflect multisystem disease necessitates close liaison with specialists from other fields. A multidisciplinary approach to the management of these patients is strongly encouraged as some will have unusual diseases that require specialist advice. It is not difficult to appreciate how the patient with monoarthritis can present the clinician with a fascinating diagnostic and therapeutic challenge, which we hope this article will help to unravel.

Induction of the mtrCDE-encoded efflux pump system of Neisseria gonorrhoeae requires MtrA, an AraC-like protein

The mtr (multiple transferable resistance) gene complex in Neisseria gonorrhoeae encodes an energy-dependent efflux pump composed of the MtrC-MtrD-MtrE cell envelope proteins that serves to export structurally diverse antimicrobial, hydrophobic agents (HAs). Many of these agents have membrane-acting detergent activity. Using Triton X-100 (TX-100) as a representative HA, we found that the mtrCDE efflux pump operon could be induced to higher levels of expression when an HA-sensitive strain was exposed to sublethal concentrations of this non-ionic detergent and the structurally related spermicide, nonoxynol-9. This induction was at the level of mtrCDE gene transcription and was independent of the MtrR repressor, which normally decreases mtrCDE gene expression. However, the enhanced resistance of gonococci to TX-100 was dependent on the expression of a previously undescribed gonococcal protein that belonged to the AraC/XylS family of transcriptional activators. We have termed this protein MtrA to signify its likely role in the activation of mtrCDE gene expression. Taken together with previous studies dealing with the genetic control of mtrCDE gene expression, we propose that gonococci can modulate their resistance to HAs through both positive and negative transcriptional control processes. The action of these regulatory processes is probably of importance in determining the survival capacity of gonococci at mucosal surfaces that contain detergent-like HAs.

Gonococcal arthritis

Disseminated gonococcal infection is the most common systemic complication of acute gonorrhea and occurs in 0.5% to 3.0% of patients with untreated mucosal infection. It is also the most common cause of septic arthritis in patients less than 30 years of age. Fortunately, the incidence of gonorrhea is decreasing dramatically in the United States and Western Europe, although it is still high in developing countries. Increasing resistance to antibiotics requires continuous surveillance of antimicrobial susceptibilities to determine the efficacy of current therapeutic measures.

Influence of ovarian hormones on urogenital infection

Numerous studies have examined the influence of hormones on infectious diseases and there is now a wealth of data relating to the more specific effect of the sex hormones, oestrogen and progesterone, on urogenital infections. The interaction between these hormones and the immune system is complex and the variation of hormonal effect between species further complicates the true picture as related to humans. Although it is difficult therefore to draw general conclusions regarding predominant effects of specific hormones, there is the suggestion that oestrogen enhances the pathogenicity of many urogenital micro-organisms. Our understanding of the influential role played by sex hormones in disease pathogenesis is at an early stage and illustrates well the importance of drawing together and interpreting as a whole both epidemiological and molecular studies.

Biophysical and antigenic characterization of gonococcal protein I incorporated into liposomes

The major gonococcal outer membrane protein, protein I (Por), was reconstituted into liposomes composed of either 1-palmitoyl, 2-oleoyl phosphatidylcholine (POPC) or POPC:1-palmitoyl, 2-oleoyl phosphatidylethanolamine (POPE) (1:1 weight ratio) and the resulting proteoliposomes characterized with respect to their biophysical and antigenic properties. Isopycnic density gradient centrifugation studies established that essentially all of the protein was reconstituted into the lipid bilayer with no significant differences in incorporation seen as a function of lipid composition. Examination of Por orientation in these proteoliposomes revealed that over 80% of the protein was oriented facing outwards in the same 'hairpin loop' fashion found in the native bacterial membrane. Reconstituted Por proteoliposomes exhibited a mean vesicle diameter of > 0.5 micron but could be reduced by extrusion without significant loss of protein or lipid. These extruded systems were suitable for sterilization by terminal filtration. The antibody binding activities of various Por liposome formulations were determined using both anti-Por monoclonal antibodies and an immunized rabbit sera. No significant differences in antibody binding were observed as a function of proteoliposome lipid composition. However, consistently higher levels of antibody binding were obtained for Por liposomes prepared in this way compared with reconstituted systems prepared as described in earlier publications.