Lymphadenitis caused by nontuberculous mycobacteria has an excellent prognosis. Surgical excision of cervical lymphadenitis caused by nontuberculous mycobacteria is curative in >97% of cases.
The incidence of suppurative regional lymphadenitis reflects the incidence of predisposing conditions, such as dental disease, streptococcal pharyngitis, otitis media, impetigo, and other infections involving the face and scalp. There are no guidelines to prevent lymphadenitis caused by nontuberculous mycobacteria.
Meningitis, inflammation of the leptomeninges, can be caused by bacteria, viruses, or, rarely, fungi. The term aseptic meningitis refers principally to viral meningitis, but meningitis with negative cerebrospinal fluid (CSF) bacterial cultures may be seen with other infectious organisms (Lyme disease, syphilis, tuberculosis), parameningeal infections (brain abscess, epidural abscess, venous sinus empyema), chemical exposure (nonsteroidal anti-inflammatory drugs, intravenous immunoglobulin), autoimmune disorders, and other diseases.
The organisms commonly causing bacterial meningitis (Table 100-1) before the availability of current conjugate vaccines were Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. In the United States, the rates of H. influenzae type b and S. pneumoniae meningitis have declined substantially after the introduction of targeted vaccines. The bacteria causing neonatal meningitis are the same as those causing neonatal sepsis (see Chapter 65). Staphylococcal meningitis occurs primarily after neurosurgery or penetrating head trauma.
Partially treated meningitis refers to bacterial meningitis complicated by antibiotic treatment before the lumbar puncture, which may result in negative CSF cultures, although other CSF findings suggestive of bacterial infection persist. The etiology can sometimes be confirmed by polymerase chain reaction of the CSF.
Viral meningitis is caused principally by enteroviruses andparechoviruses. Fecal excretion and transmission are continuous and persist for several weeks. Enteroviruses, parechoviruses, and arboviruses (St. Louis, LaCrosse, West Nile,California encephalitis viruses) are the principal causes ofmeningoencephalitis (see Chapter 101). Other viruses thatcause meningitis include herpes simplex virus, Epstein-Barrvirus, cytomegalovirus, lymphocytic choriomeningitis virus,and human immunodeficiency virus (HIV). Mumps virus isa common cause of viral meningitis in unvaccinated children.Less frequent causes of meningitis include Borrelia burgdorferi (Lyme disease), Bartonella henselae (cat-scratch disease),Mycobacterium tuberculosis, Toxoplasma, fungi (Cryptococcus,
Histoplasma, Blastomycosis, and Coccidioides), and parasites(Angiostrongylus cantonensis, Naegleria fowleri, and Acanthamoeba).
The incidence of bacterial meningitis is highest among children under 1 year of age. Extremely high rates are found in Native Americans, Alaskan Natives, and Australian aboriginals, suggesting that genetic factors play a role in susceptibility. Other risk factors include acquired or congenital immunodeficiencies, hemoglobinopathies such as sickle cell disease, functional or anatomic asplenia, and crowding such as occurs in some households, day care centers, or college and military dormitories. A CSF leak (fistula), resulting from congenital anomaly or following a basilar skull fracture, increases the risk of meningitis, especially that caused by S. pneumoniae.