Pyogenic cocci 王淑鶯 微生物免疫學所 國立成功大學醫學院 分機 :

Neisseriaceae Name after the German physician A. L. S. Neisser, who originally described the organism responsible for gonorrhea Three genera: Neisseria, Eiknella and Kingella

Neisseria gonorrhoeae Neisseria meningitidis Human Pathogens Other species normally colonize mucosal surfaces of oropharynx and nasopharynx and occasionally anogenital mucosal membranes. These species have limited virulence and generally produce disease only in compromised patients.

Neisseria N. gonorrhoeae (gonococcus): gonorrhea N. meningitidis: meningitis Gram-negative coccid-shaped (resemble coffee bean), usually in pairs. oxidase-positive; most catalase-positive N. gonorrhoeae oxidizing glucose N. meningitidis oxidizing glucose and maltose Meningococci and gonococci grow best in medium containing complex organic substances (e.g. blood, hemin, and animal proteins), and in a humid atmosphere containing 5% CO 2 N. gonorrhoeae does not grow on blood agar, but grow on chocolate agar. Physiology and Structure

Grow best under aerobic conditions Meningococci and gonococci are rapidly killed by drying, sunlight, moist heat and many disinfectants. Poor survival at cooler temperature. Peptidoglycan sandwiched between inner and outer membrane Both meningococci and gonococci are encapsulated: menigococci have a polysaccharide capsule (infection caused by serogroup A, B, C, Y, W135); gonococci have a loose capsule-like structure.

Pili: extend from cytoplasmic membrane; enhancing attachment to host cells and resistance to phagocytosis; composed of pilins; antigenically different among strains (distinct forms of pilin that is highly variable in C-terminus) makes gonorrehea vaccine difficult. Porin proteins: integral membrane proteins that form channels for nutrients to pass into cells and waste to exit; PorA and PorB are expressed in N. meningtidis, but only PorB expressed in N. gonorrhoeae; mediate resistance to neutrophil and serum killing. Opa proteins: membrane proteins; mediate binding to epithelial and phagocytic cells; associated with opaque colonies which recovered in patients with localized infection (endocervcitis,etc); transparent colonies associated with pelvic inflammatory disease and disseminated disease Antigenic structure

Rmp proteins (reduction-modifiable proteins): stimulates antibodies that block serum bactericidal activity. Binding to human transferrin for iron that is essential for growth and metabolism (other bacteria use siderophore for iron binding) Lipooligosaccharide (LOS): composed of lipid A, core polysaccharide, but lack O-specific polysaccharide. Lipid A possess endotoxin activity. Rapid growth release outer membrane blebs: contain LOS and surface protein; enhance endotoxin-mediated toxicity and protect replicating bacteria IgA1 protease: cleave hinge region of IgA; create immunologically inactive Fc and Fab  -lactamases

Pathogenesis and Immunity Attachment to mucosal cells (requires pili) Invade into the cells and multiply (Opa mediates tighter association with and invasion of host cells; Por inhibits phagolysosome fusion) Pass through the cells into the subepithelial space Establish infection (LOS stimulates inflammatory response; Rmp blocks bactericidal activity) IgG3: predominant antibodies response to gonococcal infection Meningococcal disease occurs in patients lack specific antibodies (children younger than 2 years) Patients with deficiencies in C5, C6, C7 and C8 of complement system are 6000-fold greater risk for Meningococcal disease

Gonorrhea occurs naturally only in humans. Gonorrhea is transmitted by sexual contact, often by women and men with asymptomatic infections. The most common sexually transmitted disease (second to chlamydia) Women have a 50% risk of acquiring the infection with a single exposure to an infected man while men have a 20% risk in the same situation. 95% infected men and 50% infected women have acute symptoms. So, asymptomatic carriage is more common in women than in men. Rectal and pharyngeal infections are more commonly asymptomatic than genital infections. Epidemiology N. gonorrhoeae

Endemic meningococcal disease occurs worldwide. Epidemics occurs in developing countries. In Europe and USA, serogroups B, C, Y predominate in meningitis and meningococcemia. In developing country, serogroups A and W135 predominate. Serogroups Y and W135 commonly associated with meningococcal pneumonia. Humans are the only natural carriers. Transmitted by respiratory droplets among people in close contact (family members; soldiers in military barracks; direct contact with the respiratory secretions of an infected person.) Reduction of personal contacts in a population with a high carrier rate is important for prevention. N. meningitidis

Clinical Diseases of N. gonorrhoeae male: purulent urethral discharge after 2-5 days incubation period; 95% of infected men have acute symptoms; complications are rare, but epididymi ( 附睪炎 ), prostatitis ( 攝護腺炎 ), periurethral abscess may occur. female: cervix is the primary site of infection; vaginal discharge, dysuria, abdominal pain; 10-20% infected women with salpingitis ( 輸卵管炎 ), tuboovarian abscesses ( 輸卵管卵巢膿腫 ), pelvic inflammatory disease. Gonorrhea

Disseminated infection with septicemia and infection of skin and joints 1-3% of infected women and much lower percent of infected men Symptoms: fever, migratory arthralgias ( 移動性關節痛 ) and suppurative arthritis in wrists, knees and ankles, pustular ( 膿泡 ) rash over the extremities Gonococcemia Other N. gonorrohea syndromes Perihepatitis ( 肝周圍炎 ), purulent conjunctivitis ( 化膿性結膜炎 ), ophthalmia neonatorum, anorectal gonorrhea, pharyngitis

800 cases were reported in USA in 2010 Symptoms: begins suddenly with headache, meningeal signs and fever; young children have nonspecific signs like fever and vomiting Mortality: nearly 100% if untreated; <10% in patients treated promptly with appropriate antibiotics. Neurologic sequelae: uncommon; hearing deficit. Meningitis Clinical Diseases of N. meningitidis

A life-threating disease Thrombosis ( 血栓形成 ) of small blood vessels and multiorgan involvement High fever and hemorrhagic rash A milder septicemia with low-grade fever, arthritis, and petechial skin lesions that persist for days or weeks may be observed. Other syndromes pneumonia, arthritis, and urethritis. Meningococcemia

Laboratory Diagnosis N. gonorrhoeae Gram stain (gram-negative diplococci in PMNs): Sensitive (>90%) and specific (98%) for men with purulent urethritis. Less sensitive for asymptomatic men (<60%). Relatively insensitive for both symptomatic and asymptomatic women. * Negative results must be confirmed by culture. Culture: Avoid drying of specimen (genital or rectal) and low temperature. Direct inoculation of specimens onto prewarmed media is preferred. Inoculate both the selective media (e.g., modified Thayer-Martin) and non-selective media (e.g., chocolate blood agar; for strains that are sensitive to vancomycin).

Identification: N. gonorrhoeae is distinguished from other species by acid production from oxidation of glucose, but not from other sugars. Direct detection of N. gonorrhoeae in clinical specimens by PCR with specific primers.

Specimen: blood and cerebrospinal fluid (CSF). >10 7 bacteria/ml of CSF are normally found in untreated patients. Gram stain: gram-negative diplococci in PMNs. Culture: alternative blood culture methods are required because additives in the blood culture broths can be toxic for this organism. Identification: acid formation with glucose and maltose, but not others. N. meningitidis

Resistance to penicillin G (PPNG: penicillinase-producing N. gonorrhoeae) and tetracycline is common. Resistance to fluoroquinolones has also become prevalent. Ceftriaxone can be used for uncomplicated gonorrhea. Combined with 1-week dose of doxycycline or single dose of azithromycin for dual infections with Chlamydia. Chemoprophylaxis is ineffective except for newborn eye infections (1% silver nitrate, 1% tetracycline or 0.5% erythromycin). Protective immunity to reinfection does not develop due to the antigenic variation of gonococci. This makes development of effective vaccines difficult. Treatment, Prevention and Control

Rifampin, ceftriaxone, or ciprofloxacin can often eradicate the carrier state and serve as chemoprophylaxis for preventing N. meningitidis infection. Vaccination of specific capsular polysaccharides of groups A, C, Y, and W-135 is used for protecting susceptible persons against infection. - polysaccharide vaccine - polysaccharide-protein conjugate vaccine (11-18 years old) Outer membrane vesicle vaccines for group B (weak immunogen) are being developed recently.