Treatment This is in two phases, an intesive eradication component with high intravenous doses of ceftazidime (or several equivalent regimens) for 10 to 14 days, followed by an eradication phase that is necessary to prevent relapse, using trimethoprim/sulfamethoxazole alone or accompanied by doxycycline.
This potentially fatal respiratory disease caused by the gram-negative bacillus Legionella pneumophila, first came to medical notice in July 1976, when a large number of members of the American Legion fell ill at their annual convention in Philadelphia. The fatality rate was high. In addition to the obvious pulmonary infection, manifestations referable to the CNS and other organs were observed regularly. Lees and Tyrrell described patients with severe and diffuse cerebral involvement, and Baker and associates and Shetty and colleagues described others with cerebellar and brainstem syndromes. The clinical details have varied. One constellation consisted of headache, obtundation, acute confusion or delirium with high fever, and evidence of pulmonary distress; another took the form of tremor, nystagmus, cerebellar ataxia, extraocular muscle and gaze palsies, and dysarthria.
Other neurologic abnormalities have been observed, such as inappropriate ADH secretion, or a syndrome of more diffuse encephalomyelitis or transverse myelitis, similar to that observed with Mycoplasma infections. The CSF is usually normal and CT scans of the brain are negative, a circumstance that makes diagnosis difficult. Suspicion of the disease, based on exposure or on the presence of an atypical pneumonia, should prompt urine antigen and culture of blood and CSF. Serologic tests are available but require paired sera and have little impact on clinical decision making. In most patients the signs of CNS disorder resolve rapidly and completely, although residual impairment of memory and a cerebellar ataxia have been recorded. To date, the Legionella bacillus has only rarely been isolated from the brain or spinal fluid.
Treatment Treatment in adults has consisted of one of levofloxacin, moxifloxacin, or azithromycin; rifampin is sometimes used. In the past, erythromycin, 0.5 to 1.0 g was used intravenously q6h for a 7 to 10 days.
Reports of over 100 cases of encephalitis from catscratch disease have appeared in the medical literature and several have occurred on our services over the years, for which reason we do not consider it rare. The causative organism is a gram-negative bacillus now called Bartonella henselae (formerly Rochalimaea henselae). The illness begins as unilateral axillary or cervical adenopathy occurring after a seemingly innocuous scratch (rarely a bite) from an infected cat. The cases with which we are familiar began with an encephalopathy and high fever (higher temperature than with most of the other organisms that are capable of causing bacterial encephalitis), followed by seizures or status epilepticus. The organism has also been implicated in causing a focal cerebral vasculitis in HIV patients as well as optic neuritis and neuroretinitis in both immunocompromised and immunocompetent patients. Demonstration of elevated complement-fixing titers and detection of the organism by PCR or by silver staining from an excised lymph node are diagnostic. A single high antibody titer is probably inadequate for this purpose.
Treatment First-line treatment is with azithromycin or doxycycline, sometimes with rifampin in recalcitrant cases. Erythromycin is used less frequently. Most patients recover completely, but one of our patients and a few reported by others have died.