Gram Negative Cocci: the Neisseria

Introduction The family Neisseriaceae comprises the genera - Neisseria - Moraxella - Kingella - Eikenella. Neisseria gonorrhea and Neisseria meningitidis are the most significant human pathogens.

General Characteristics of Neisseria spp. Aerobic, Gram-negative cocci, 0.6 to 1.0 um in diameter, often arranged in pairs (diplococci) with adjacent sides flattened (like coffee beans) Neisseria meningitidis is encapsulated whereas Neisseria gonorrhea is not Oxidase positive Most catalase positive Nonmotile Acid from oxidation of carbohydrates, not from fermentation

Neisseria gonorrhea infections have a high prevalence and low mortality whereas Neisseria meningitidis infections have a low prevalence and high mortality. Other species normally colonize mucosal surfaces of oropharynx and nasopharynx and occasionally anogenital mucosal membranes

They have pili and an outer membrane with highly branched basal oligosaccharides but no repeating O- antigen subunits. They release outer membrane fragments (blebs) during growth which contain LOS and may have a role in pathogenesis. Both of Neisseria gonorrhea and Neisseria meningitidis produce IgA1 protease.

Neisseria Associated Diseases (ophthalmia neonatorum)

Neisseria gonorrhea The gonococcus is an obligate human pathogen. They attach to mucosal cells via pili and a protein present in the outer membrane(Opa or protein II). Gonococci attach only to microvilli of nonciliated columnar epithelial cells, attachment to ciliated cells is not observed. Endocytosis follows attachment.

Gonococcal infections are acquired by sexual contact and usually affect mucous membranes of the urethra in men and the endocrvix in women. Individuals with inherited complement deficiencies have a markedly increased risk of developing systemic infection by Neisseria and are subject to recurring episodes of systemic gonococcal and meningococcal infections .

Pathogenesis of Neisseria gonorrhoeae Fimbriated cells attach to intact mucus membrane epithelium Capacity to invade intact mucus membranes or skin with abrasions Adherence to mucosal epithelium Penetration into and multiplication before passing through mucosal epithelial cells Establish infection in the sub-epithelial layer Most common sites of inoculation: Cervix (cervicitis) or vagina in the female Urethra (urethritis) or penis in the male

Gonococcal Virulence Factors Antiphagocytic capsule-like negative surface charge Only fimbriated (piliated) cells (formerly known as colony types T1 & T2) are virulent Outer membrane proteins (formerly Proteins I, II, & III) Por (porin protein) prevents phagolysosome fusion following phagocytosis and thereby promotes intracellular survival Opa (opacity protein) mediates firm attachment to epithelial cells and subsequent invasion into cells Rmp (reduction-modifiable protein) protects other surface antigens from bactericidal antibodies (Por protein, LOS) Acquisition of iron mediated through Tbp 1 and Tbp 2 (transferrin-binding proteins), Lbp (lactoferrin binding protein) & Hbp (hemoglobin-binding protein)

Gonococcal Virulence Factors (cont.) Llipooligosaccharide (LOS) (Lipid A plus core polysaccharide but no O-somatic antigen polysaccharide side chain) has endotoxin activity IgA1 protease Acquisition in last two decades of two types of antibiotic resistance: Plasmid-encoded beta-lactamase production Chromosomally-mediated changes in cellular permeability inhibit entry of penicillins, tetracycline, erythromycin, aminoglycosides

Clinical Manifestations Gonorrheal infection is generally limited to superficial mucosal surfaces lined with columnar epithelium. The areas most frequently involved are the cervix, urethra, rectum, pharynx and conjunctiva. Squamous epithelium (adult vagina) is not susceptible (gonorrhea in young girls may present as vulvovaginitis). Mucosal infections are usually characterized by a marked local neutrophilic response (purulent discharge)

The most common symptom of uncomplicated gonorrhea is a discharge that may range from a scanty, clear or cloudy fluid to one that is copious and purulent. Dysuria is often present. Endocervical infection is the most common form of uncomplicated gonorrhea in women manifesting as vaginal discharge and dysuria. About 50% of those women are asymptomatic

Rectal infection occurs in about one third of women with cervical infection resulting form autoinoculation with cervical discharge and are rarely symptomatic. Rectal infection in homosexual men is commonly symptomatic. Pharyngeal infection in men or women may be a focal source of gonococcemia. Ocular infection can have serious consequences (corneal scarring or perforation)

Disseminated infection result from gonococcal bacteremia. The most common form of disseminated gonococcal infection is the dermatitis –arthritis syndrome. It is characterized by fever, chills, skin lesions (macular, pustular, necrotic or hemorrhagic) and arthralgia (hands, feet, elbow) due to periarticular inflammation of the tendon sheaths. Occasionally a patient develops a septic joint with effusion. Rarely endocarditis or meningitis develop.

Gonococci may ascend from the endocervical canal through the endometrium to the Fallopian tubes and ultimately to the pelvic peritoneum resulting in endometiritis, salpingitis and finally peritonitis. Women usually present with pelvic and abdominal pain, fever, chills and cervical motion tenderness. This complex of signs and symptoms is referred to as pelvic inflammatory disease (PID).

Complications of PID include tubo - ovarian abscess, pelvic peritonitis or Fitz – Hugh and Curtis syndrome (inflammation of Glisson's capsule of the liver). As many as 15% of woman with uncomplicated cervical infection may develop PID which may have serious consequences including an increased probability of infertility and ectopic pregnancy.

Epidemiology of Gonorrhea Seriously underreported sexually-transmitted disease 350,000 reported cases in USA in 1998 Down from 700,00 cases in 1990 Found only in humans with strikingly different epidemiological presentations for females and males Asymptomatic carriage is major reservoir Transmission primarily by sexual contact Lack of protective immunity and therefore reinfection, partly due to antigenic diversity of strains Higher risk of disseminated disease in patients with late complement deficiencies

Epidemiology A very common infectious disease (2 unreported cases for each reported case). Highest rates are a among women 15-19 years and men 20-24 years of age. Gonorrhea is usually contracted from a sex partner who is either asymptomatic or has only minimal symptoms.

It is estimated that the efficiency of transmission after one exposure is about 35% from an infected woman to an uninfected man and 50-60% from an infected man to an uninfected woman. More than 90% of men with urethral gonorrhea will develop symptoms within days, fewer than 50% of woman will do so.

Differences Between Men & Women with Gonorrhea IN MEN: Urethritis; Epididymitis Most infections among men are acute and symptomatic with purulent discharge & dysuria after 2-5 day incubation period Male host seeks treatment early preventing serious sequelae, but not soon enough to prevent transmission to other sex partners The two bacterial agents primarily responsible for urethritis among men are N. gonorrhea and Chlamydia trachomatis

Differences Between Men & Women with Gonorrhea (cont.) IN WOMEN: Cervicitis; Vaginitis; Pelvic Inflammatory Disease (PID); Disseminated Gonococcal Infection (DGI) Women often asymptomatic or have atypical indications (subtle, unrecognized S/S); Often untreated until PID complications develop Pelvic Inflammatory Disease (PID) May also be asymptomatic, but difficult diagnosis accounts for many false negatives Can cause scarring of fallopian tubes leading to infertility or ectopic pregnancy

Differences Between Men & Women with Gonorrhea (cont.) IN WOMEN (cont.) : Disseminated Gonococcal Infection (DGI): Result of gonococcal bacteremia Often skin lesions Petechiae (small, purplish, hemorrhagic spots) Pustules on extremities Arthralgias (pain in joints) Tenosynovitis (inflammation of tendon sheath) Septic arthritis Occasional complications: Hepatitis; Rarely endocarditis or meningitis

Prevention & Treatment Penicillin no longer drug of choice due to: Continuing rise in the MIC Plasmid-encoded beta- lactamase production Chromosomally-mediated resistance Uncomplicated infection: ceftriaxone, cefixime or fluoroquinolone Combined with doxycycline or azithromycin for dual infections with Chlamydia

Chemoprophylaxis of newborns against ophthalmia neonatorum with 1% silver nitrate, 1% tetracycline, or 0.5% erythromycin eye ointments Treatment of newborns with opthalmia neonatorum with ceftriaxone Measures to limit epidemic include education, aggressive detection, and follow-up screening of sexual partners, use of condoms or spermicides with nonoxynol 9

General Overview of Neisseria meningitidis Encapsulated small, gram-negative diplococci Second most common cause (behind S. pneumoniae) of community-acquired meningitis in previously healthy adults; swift progression from good health to life-threatening disease Pathogenicity: Pili -mediated, receptor-specific colonization of nonciliated cells of nasopharynx Antiphagocytic polysaccharide capsule allows systemic spread in absence of specific immunity Toxic effects mediated by hyperproduction of lipooligosaccharide

Neisseria Meningitidis Meningococcal capsular polysaccharide provide the basis for grouping these organisms. Thirteen serogroups have been identified (A,B,C,H, I, J, K, L, 29 E, X, Z, Y and W135). Serogroups A, B, C, Y, and W135 account for about 90% of all infections A few serotypes are associated with most cases of meningococcal disease whereas other serotypes rarely caused disease.

Diseases Associated with Neisseria meningitidis Following dissemination of virulent organisms from the nasopharynx: Meningitis Septicemia (meningococcemia) with or without meningitis Meningoencephalitis Pneumonia Arthritis Urethritis

The human nasopharnx is the only known reservoir of N.meningitidis. Meningococci are spread via respiratory droplets and transmission requires aspiration of infective particles. They attach to the nonciliated columnar epithelial cells of the nasopharnx via pili and outer membrane proteins. They reach the blood stream and the events after blood stream invasion are unclear.

The integrity of the pharyngeal and respiratory epithelium may be important in protection from invasive disease. The presence of serum bactericidal IgG and IgM is probably the most important host factor in preventing invasive disease. Persons with complement deficiencies (C5, C6, C7 or C8) may develop meningococcemia despite protective antibody (6000 fold increase of risk).

Pathogenesis of Meningococcal Disease Specific receptors (GD1 ganglioside) for bacterial fimbriae on nonciliated columnar epithelial cells in nasopharynx of host Organisms are internalized into phagocytic vacuoles, avoid intracellular killing in absence of humoral immunity and complement system (patients with late complement deficiencies are particularly at risk) Replicate intracellularly and migrate to subepithelial space where excess membrane fragments are released Hyperproduction of endotoxin (lipid A of LOS) and blebbing into surrounding environment (e.g., subepithelial spaces, bloodstream) mediates most clinical manifestations including diffuse vascular damage (e.g., endothelial damage, vasculitis (inflammation of vessel walls), thrombosis (clotting), disseminated intravascular coagulation (DIC)

Skin Lesions of Meningococcemia NOTE: Petechiae have coalesced into hemorrhagic bullae.

Immunogenicity of Neisseria meningitidis Following colonization of the nasopharynx, protective humoral immunity develops against the same or closely related organisms of the same serogroup, but not against other serogroups Bactericidal activity of the complement system is required for clearance of the organisms Cross-reactive protective immunity acquired with colonization by closely related antigenic strains and with normal flora of other genera (e.g., E. coli K1); progressive disease can occur in absence of serogroup-specific immunity

Clinical Manifestations N. meningitides infection usually results from the blood borne dissemination (meningococcemia) usually following an asymptomatic or mildly symptomatic nasopharyngeal carrier state or a mild rhinopharyngitis. The mildest form is a transient bacteremic illness characterized by fever and malaise that resolves in 1-2 days. Acute meningococcemia is more serious and is often complicated by meningitis. The manifestations of meningococcal meningitis are similar to acute bacterial meningitis caused by organisms such as S. pneumoniae, H. influenzae and E. coli.

Manifestations result from both infection and increased intracranial pressure. Chills , fever , malaise and headache are the usual manifestations of infection. Headache, photophobia, vomiting and rarely papilledema may result from increased intracranial pressure. Signs of meningeal inflammation are also present. The onset of meningitis may be abrupt or insidious.

Infants with meningococcal meningitis rarely display signs of meningeal irritation and fever is typically absent in children younger than 2 months of age (apneic episodes, seizures and coma). Neurologic signs are common; convulsions, or signs of meningeal irritation such as cervical rigidity (Brudzinski sign) thoracolumbar rigidity, hamstring spasm (Kerning sign) and exaggerated reflexes are common. Petechiae or purpura occur from the first to the third day of illness in 30 -60% of patients.

Fulminant meningococcemia (Waterhouse – Friderichsen syndrome) occurs in 5-15% of patients with meningococcal disease and has a high mortality rate. It begins abruptly with high fever, chills, myalgias, weakness, nausea, vomiting and headache. Apprehension, restlessness, and frequently delirium occur within the next few hours.

Widespread purpuric and ecchymotic skin lesions appear suddenly. Typically, no signs of meningitis are present. Pulmonary insufficiency develops within a few hours and many patients die within 24 hours of being hospitalized despite appropriate antibiotic therapy and intensive care.

Diagnosis – Smears – Culture – Antigen Detection

Prevention and Treatment of Meningococcal Disease Penicillin is the drug of choice for treatment in adjunct with supportive therapy for meningeal symptoms Increasing MIC mediated by genetic alteration of target penicillin binding proteins is being monitored) Chloramphenicol or cephalosporins as alternatives Chemoprophylaxis of close contacts with rifampin or sulfadiazine (if susceptible) Polyvalent vaccine containing serogroups A, C, Y, and W135 is effective in people older than 2 years of age for immunoprophylaxis as an adjunct to chemoprophylaxis Serogroup B is only weakly immunogenic and protection must be acquired naturally from exposure to cross-reacting antigens

Epidemiology of Meningococcal Disease Humans are the only natural hosts Person-to-person transmission by aerosolization of respiratory tract secretions in crowded conditions Close contact with infectious person (e.g., family members, day care centers, military barracks, prisons, and other institutional settings) Highest incidence in children younger than 5 years and particularly those younger than 1 year of age as passive maternal antibody declines and as infants immune system matures Commonly colonize nasopharynx of healthy individuals; highest oral and nasopharyngeal carriage rates in school-age children, young adults and lower socioeconomic groups

Epidemiology N. meningitidis is normally present in the nasopharynx of 5-10 % of normal individuals at any given time, yet few develop disease. Carriage rates increase to 50% or more during epidemics. Disease occurs sporadically or in epidemics. Most epidemics are caused by group A strains, less so with B and C strains

Group A, C, Y and W132 capsular polysaccharide vaccines are available and can be used to control outbreaks. The group B capsular polysaccharide is a homopolymer of sialic acid and is not immunogenic in humans. House hold contacts of cases are at 500-800 fold greater attack rate, therefore should receive chemoprophylaxis.

Moraxella Gram negative diplococci, oxidase and catalase positive They are commensals of mucosal surfaces and occasionally give rise to opportunistic infections Most important species is M. catarrhalis It is associated with pneumonia, meningitis, endocarditis, conjunctivitis, sinusitis, and otitis. It is occasionally isolated from the blood of immunocompromised individuals.

Kingella and Eikenella Kingella are catalase negative, oxidase positive, and glucose fermenting coccobacilli Kingella kingae is associated with endocarditis and infection of bone, joints and tendons Eikenella corrodens is a small, oxidase positive, fastidious, capnophilic gram negative rod that is part of the gingival and bowel flora of 40-70% of humans It is found in mixed infections and those caused by human bites