Anthrax Meningoencephalitis

Infection with Bacillus anthracis is acquired through cutaneous contact, inhalation, or ingestion. The bacilli

FIGURE 6.1

Acute purulent leptomeningitis caused by P-hemolytic streptococci in a 71-year-old man. A. Thick yellow exudate fills the subarachnoid space over the lateral aspects of the cerebral hemispheres. B. Dense exudate of PNLs, a few lymphocytes and erythrocytes, and some fibrin fills the subarachnoid space (HE).

FIGURE 6.1

Acute purulent leptomeningitis caused by P-hemolytic streptococci in a 71-year-old man. A. Thick yellow exudate fills the subarachnoid space over the lateral aspects of the cerebral hemispheres. B. Dense exudate of PNLs, a few lymphocytes and erythrocytes, and some fibrin fills the subarachnoid space (HE).

FIGURE 6.2

Fulminant meningococcus meningitis. An 18-year-old male presented in the emergency room with a sudden onset of headaches, fever, and generalized malaise. Examination of the CSF revealed an increased cell count with PNLs, increased protein levels, and the presence of gram-negative meningococci. On the second day, he developed purpuric skin rashes and required assisted ventilation. Soon he went into septic shock, eventually became comatose and, on the fourth day of his illness, he died. At autopsy, both adrenal glands were hemorrhagic. A. The brain is markedly swollen, the leptomeninges clouded, and the blood vessels congested. Patchy and confluent hemorrhages fill the basal subarachnoid space. B. The subarachnoid space is filled with PNLs, red blood cells, macrophages, and fibroblasts. The exudate extends into the superficial cortical layers. C. The cerebral cortex is hemorrhagic and necrotic (HE).

FIGURE 6.2

Fulminant meningococcus meningitis. An 18-year-old male presented in the emergency room with a sudden onset of headaches, fever, and generalized malaise. Examination of the CSF revealed an increased cell count with PNLs, increased protein levels, and the presence of gram-negative meningococci. On the second day, he developed purpuric skin rashes and required assisted ventilation. Soon he went into septic shock, eventually became comatose and, on the fourth day of his illness, he died. At autopsy, both adrenal glands were hemorrhagic. A. The brain is markedly swollen, the leptomeninges clouded, and the blood vessels congested. Patchy and confluent hemorrhages fill the basal subarachnoid space. B. The subarachnoid space is filled with PNLs, red blood cells, macrophages, and fibroblasts. The exudate extends into the superficial cortical layers. C. The cerebral cortex is hemorrhagic and necrotic (HE).

produce an acute, fulminant meningitis or meningoencephalitis with a high mortality rate. Examination of the CSF, which is usually bloody, yields an elevated white cell count, a high protein level, a low glucose level, and the presence of gram-positive bacilli. Computed tomography (CT) scan and magnetic resonance imaging (MRI) reveal subarachnoid and parenchymal hemorrhages and, with the use of contrast material, enhance the leptomeninges.

The cerebral pathology is characterized by a purulent, hemorrhagic exudate in the subarachnoid space. Necrotizing vasculitis, inflammatory infiltrates, and multiple hemorrhages and infarcts characterize the parenchymal changes. The bacilli are readily demonstrated using Gram stain.

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