Figure 156.1 Thumb with skin ulcer of tularemia (Public Health Image Library, Centers for Disease Control and Prevention [CDC]).
Diagnosis of tularemia is based on positive tissue culture or, more commonly, serology. Growth of F. tularensis in culture, from lymphatic tissue, blood, surface swabs, or other infected tissue, is the definitive means of confirming the diagnosis of tularemia. Because F. tularensis has been associated with laboratory-acquired infections laboratory personnel should be notified of the diagnostic possibility to enhance the diagnostic yield and to ensure that safety procedures are followed. Since the organism grows poorly on standard media, it must be grown on media enriched with cysteine (e.g., modified Thayer–Martin media, chocolate agar) and may take upwards of 10 days of incubation for growth.
The diagnosis of tularemia is usually established by serologic testing; a ≥4-fold change in F. tularensis agglutinin titer between acute and convalescent sera confirms the diagnosis, whereas a single convalescent titer of ≥160 is consistent with recent or past infection. In patients with tularemia, antibodies appear approximately 2 to 3 weeks after infection and may be detected several years after recovery.
To date there have been no randomized controlled trials to determine the optimal antimicrobial therapy for tularemia treatment. In the past streptomycin has been the drug of choice in treating this infection. In one meta-analysis the use of streptomycin was associated with a 97% clinical cure rate compared to only 86% with gentamicin. In one series, involving only