TULAREMIA: DIAGNOSIS, TREATMENT AND POSTEXPOSURE PROPHYLAXIS
TULAREMIA: DIAGNOSIS, TREATMENT AND POSTEXPOSURE PROPHYLAXISDiagnosisThe clinical presentation and laboratory features of tularemia are generally nonspecific. Radiographic findings include lobar consolidations, miliary infiltrates, hilar or mediastinal lymphadenopathy, or pleural effusions, but these, too, are nonspecific. As with the other diseases caused by the agents of bioterrorism, clinical suspicion is necessary for diagnosis. Physicians who suspect this disease should alert local or state public health authorities so that the appropriate epidemiologic and environmental investigations can be begun. The clinical microbiology laboratory should also be warned of the diagnosis, since isolation of the organism represents a clear hazard to laboratory personnel.Francisella tularensis may be directly identified in human tissues or body fluids using antigen detection assays (direct fluorescent antibodies or immunohistochemical stains). A diagnosis can also be made by recovery of the organism from cultures of blood, ulcers, conjunctival exudates, sputum, gastric aspirates, and pharyngeal washings, although these should only be attempted in Biosafety Level-3 containment facilities. The organism is quite fastidious, and growth may be delayed, so cultures should be held for 10 days before discarding. Culture may still be possible after the initiation of appropriate antimicrobial therapy. Most diagnoses of tularemia are made serologically, and a fourfold change in titer between acute and convalescent serum specimens or a single titer of at least 1:160 is diagnostic for infection. Serum titers usually do not reach diagnostic levels until 10 or more days after the onset of illness.
Treatment and Postexposure ProphylaxisStreptomycin has historically been the drug of choice for tularemia, but alternative therapies should be considered, since this antibiotic is not readily available. Gentamicin is an acceptable alternative, and treatment should be continued for 10 days. Ciprofloxacin, which has intracellular activity, has been used successfully to treat tularemia after 10 days of therapy. Doxycycline and chloramphenicol can also be used, but since these drugs are bacteriostatic, therapy should be continued for at least 14 days to reduce the risk of treatment failure and relapses.In a bioterrorist release, exposed persons should be prophylactically treated with a 2-week course of either oral ciprofloxacin (500 mg twice daily) or doxycycline (100 mg twice daily). These individuals should be instructed to begin a fever watch.
Infection ControlIsolation is not necessary for patients with tularemia, since person-to-person transmission has not been documented. Physicians should use standard precautions when caring for patients with tularemia.*216/348/5*
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