Francisella tularensis/Rickettsia spp. co-infections in patients with skin changes and lymphadenopathy

Introduction Tularemia and spotted fever group rickettsioses (SFG) can be transmitted by ticks and have a number of common clinical symptoms. Most characteristic are a maculopapular or vesicular rash or an eschar at the site of the tick or insect bite accompanied by painful lymph nodes. The aim of this study was to determine whether Rickettsia spp./Francisella tularensis mixed infections occurred in patients with similar symptoms who were diagnosed with either Rickettsia spp. or F. tularensis infection. Material and methods Thirty-six cases from 2011-2014, including 15 individuals with clinically and serologically recognized SFG and 21 with tularemia, were analyzed retrospectively using immunofluorescence for detection of Rickettsia spp. or ELISA for detection of F. tularensis. Results Of the 36 cases examined, specific high titers of antibodies to Rickettsia spp. were found in 1 (4.4%) patient with tularemia and specific high titers of antibodies to F. tularensis were detected in 1 (6.7%) patient with SFG. Conclusions The results of our study show that in infections with fever, enlarged lymph nodes and skin lesions after tick and insect bites, laboratory testing of both diseases - SFG rickettsiosis and tularemia - should be implemented. Identification of F. tularensis and Rickettsia spp. mixed infections is crucial in order to administer appropriate antibiotics and to avoid treatment failure and relapse.