The common pathogenic Neisseria species are meningococci and gonococci. Meningococci can be cultured in up to 15% of healthy persons in nonepidemic periods. Virulence is determined by the polysaccharide capsule and the potent endotoxic activity of the cell wall, which can cause cardiovascular collapse, shock, and disseminated intravascular coagulation. Persons who are complement deficient or asplenic are at risk for serious clinical infections. Diagnostic testing may include Gram stain, blood and cerebrospinal fluid cultures, enzyme-linked immunosorbent assay (ELISA), and PCR. An automated fluorescent multiplex PCR assay that can simultaneously detect N meningitidis, H influenzae, and S pneumoniae can be used to evaluate patients with suspected meningitis. This test provides extremely high sensitivity and a specificity of 100% for each organism.
The range of meningococcal infections includes meningitis, mild to severe upper respiratory tract infections, and, less often, endophthalmitis, endocarditis, pericarditis, arthritis, and purpura fulminans. Neisseria meningitidis serogroup B is the most common cause of bacterial meningitis in children and young adults. Meningitis with a petechial or purpuric exanthem is the classic presentation, although each may occur in isolation.
Historically, the treatment of choice for meningococcal meningitis has been high-dose penicillin or, in the case of allergy, chloramphenicol or a third-generation cephalosporin. Rifampin or minocycline is used as chemoprophylaxis for family members and intimate personal contacts of the infected individual. Polysaccharide vaccines are most effective in older children and adults.
Among women with gonococcal infections, 50% are asymptomatic, whereas 95% of men with gonococcal infections are symptomatic. Asymptomatic patients are infectious for several months, with a transmissibility rate of 20%–50%. Nonsexual transmission is rare. The key to prevention is identification and treatment of asymptomatic carriers and their sexual contacts.
The range of gonococcal infections includes cervicitis; urethritis; pelvic inflammatory disease; pharyngitis; conjunctivitis; ophthalmia neonatorum; and disseminated gonococcal disease with fever, polyarthralgias, and rash. Chlamydia trachomatis coexists with gonorrhea in 25%–50% of women with gonococcal cervicitis and 20%–33% of men with gonococcal urethritis. Diagnosis of gonococcal infections, as well as infections caused by many other bacteria, mycobacteria, viruses, and Mycoplasma, has been aided by the development of highly sensitive DNA probes that use PCR techniques.
Because penicillin-resistant and tetracycline-resistant gonococcal strains have become common in many areas of the United States, treatment should be tailored to their local prevalence. Tetracycline is effective for patients who are infected by susceptible strains, are allergic to penicillin, or have concurrent chlamydial infections. Ceftriaxone (via intramuscular injection) is the drug of choice for penicillinase-resistant strains; thus far, reduced susceptibility to this antibiotic has been extremely rare. Alternatives include oral cefixime, cefuroxime, azithromycin, and the fluoroquinolones. The macrolides and fluoroquinolones have the added benefit of excellent activity against concomitant C trachomatis infection. However, gonococcal isolates with reduced sensitivity to macrolides and fluoroquinolones have been reported with increasing frequency, and the US Centers for Disease Control and Prevention (CDC) recommends that clinicians no longer use fluoroquinolones as a first-line treatment for gonorrhea, leaving cephalosporins as the only class of antimicrobials available for treatment of gonorrhea in the United States.
Grad YH, Harris SR, Kirkcaldy RD, et al. Genomic epidemiology of gonococcal resistance to extended-spectrum cephalosporins, macrolides, and fluoroquinolones in the United States, 2000–2013. J Infec Dis. 2016; 214(10):1579–1587.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.