What Is BACTERIAL DISEASES? and the number of cells in the cerebrospinal fluid is always elevated and varies between 100 and 100,000 per cubic millimeter. Initially, polymorphonuclear leukocytes predominate; these are replaced by lymphocytes as the inflammatory process progresses. Early in the infection one may f i nd a plethora of bacteria with only a few cells. This is particularly true in pneumococcal and staphylococcal infections.
A low cerebrospinal fluid sugar is the hallmark of bacterial meningitis and distinguishes it from the viral meningitides. Usually, the value is below 40 mg. per 100 ml, and maybe close to 0. Patients who have diabetes mellitus or who are receiving intravenous infusions of glucose may have falsely high glucose values. However, the ratio of blood to cerebrospinal fluid sugar in these patients is always higher than the normal value of1.5 to 1. For example, a cerebrospinal fluid sugar of 150 mg. per 100 ml. in the presence of blood sugar of 500 mg. per 100 ml. is highly significant. The information obtained from blood sugar, which should be obtained routinely at the time of initial lumbar puncture, is frequently critical.
The protein content of the cerebrospinal fluid is generally elevated and may be as high as 800 mg. per 100 ml. Higher values are usually obtained in pneumococcal meningitis than in infections with other pathogens. What Is BACTERIAL DISEASES The development of subarachnoid block is usually heralded by very high CSF protein values (800 to 1500 mg. per 100 ml.).Other Cultures. Blood cultures should be obtained routinely in patients suspected of having meningitis; they are positive in approximately50 percent of cases. Occasionally, when the cerebrospinal fluid cultures are negative, the blood cultures may provide the only clue to the etiologic agent. Nose, throat, and ear cultures may not reflect the meningeal pathogen and are misleading too often to be of more than the ancillary value in diagnosis.
Roentgenographic Studies. All patients with meningitis should have roentgenograms of the chest, skull, mastoid, and paranasal sinuses as soon as their condition permits. Frequently these provide the clue to the portal of entry of the path-gen. Eradication of these foci with antimicrobial therapy or surgical drainage may be essential for control of the meningeal infection.