infectious diseases
Anthrax
Diagnosis of Anthrax
Gram stain and culture Direct fluorescent antibody (DFA) test and polymerase chain reaction (PCR) assay Occupational and exposure history is important. Cultures and Gram stain of samples from clinically identified sites, including cutaneous or mucosal lesions, blood, pleural fluid, cerebrospinal fluid, ascites, or stool, should be done. Sputum examination and Gram stain are unlikely to identify inhalation anthrax because airspace disease is frequently absent. A PCR test and immunohistochemical methods (eg, DFA) can help. Nasal swab testing for spores in people potentially exposed to inhalation anthrax is not recommended because the negative predictive value is unknown. Although a positive nasal swab culture indicates exposure, a negative nasal swab does not mean that exposure has not occurred. Sputum examination and Gram stain are unlikely to identify inhalation anthrax because airspace disease is frequently absent. Chest x-ray (or CT) should be done if pulmonary symptoms are present. It typically shows widening of the mediastinum (because of enlarged hemorrhagic lymph nodes) and pleural effusion. Pneumonic infiltrates are uncommon. Lumbar Puncture (Spinal Tap) should be done if patients have meningeal signs or a change in mental status. If a lumbar puncture cannot be done, central nervous system imaging by CT with contrast or MRI with contrast should be done to document meningeal enhancement characteristics of meningitis and identify hemorrhagic parenchymal lesions characteristic of anthrax meningoencephalitis. An enzyme-linked immunosorbent assay (ELISA) can detect antibody in serum, but confirmation requires a 4-fold change in antibody titer from acute to convalescent specimens. 