going shunt procedures for relief of hydrocephalus tend to have infections with bacteria that are ordinarily not pathogenic such as Staphylococcus epidermidis or micrococci; gram-negative enteric bacterial and Pseudomonas meningitis also com-plicate shunting procedures. Occasionally, sub-cutaneous or mucosal infections such as furunculosis, decubitus ulcers, omphalitis in neonates, and endometritis precede leptomeningitis. Rare Types of Meningitis. Mime polymorpha Meningitis. Mima polymorpha is a gram-negative pleomorphic bacillus that is easily confused on Gram stain with members of the Neisseria group and H. influenza. It can be separated from these organisms, however, by cultural and serologic techniques. Meningitis caused by Mima poly-morphia closely resembles meningitis caused by the more common pathogens and cannot be differentiated from them on clinical grounds. Separation of an image from Neisseria is of more than academic importance because the image may be resistant to penicillin and sulfonamides and respond only to the tetracyclines.
Listeria Meningitis. The most common clinical illness caused by Listeria is meningitis, and any patient with clinical and laboratory evidence of meningeal infection said to be caused by a diphtheroid should be assumed to harbor Listeria in the cerebrospinal fluid. Clinically, the illness cannot be distinguished from meningitis caused by other bacteria (see Listeriosis). Other Organisms. Bacteria that have caused infections usually in patients with antecedent head trauma or neurosurgical procedures include Cl. perfringens and Past. multocida, although any organism can occasionally produce infection in this setting.
Recurrent bouts of meningitis are most frequently related to remote as well as to recent head trauma. The individual episodes are usually caused by the same bacterial species that are also-treated with meningitis occurring in the absence of trauma, except that pneumococci of higher serologic types are isolated more commonly than H. influenzae and Neisseria. Bouts of meningitis may be separated by an interval of several years. Cerebrospinal fluid rhinorrhea owing to a defect in the cribriform plate is often associated with recurrent meningeal infection. All patients with repeated bouts of meningitis should be subjected to a vigorous search for communication between the subarachnoid space and the nasopharynx, and if roentgenographic techniques fail to disclose the defect, craniotomy should be considered. Other situations predisposing to recurrent meningeal infections include chronic mastoiditis or petrosal-is, congenital abnormalities of the cranial vault, and congenital dermoid sinus tracts.
Ventricular-mastoid shunts aimed at relief of hydrocephalus are also complicated by recurrent infections, which are often heralded by otitis media. Recurrent bouts of meningitis have been reported in children who have undergone splenectomy; this does not appear to be true of adults. Nor is there evidence that the incidence of meningitis is increased in children with hypo- or dysgamma-globulinemia.