Rickettsia burneti and Brucella melitensis co-infection: a case report and literature review

Rickettsia is the pathogen of Q fever, Brucella ovis is the pathogen of brucellosis, and both of them are Gram-negative bacteria which are parasitic in cells. The mixed infection of rickettsia and Brucella ovis is rarely reported in clinic. Early diagnosis and treatment are of great significance to the treatment and prognosis of brucellosis and Q fever. Here, we report a case of co-infection Rickettsia burneti and Brucella melitensis. The patient is a 49-year-old sheepherder, who was hospitalized with left forearm trauma. Three days after admission, the patient developed fever of 39.0°C, accompanied by sweating, fatigue, poor appetite and headache. Indirect immunofluorescence (IFA) was used to detect Rickettsia burneti IgM. After 72 hours of blood culture incubation, bacterial growth was detected in aerobic bottles, Gram-negative bacilli were found in culture medium smear, the colony was identified as Brucella melitensis by mass spectrometry. Patients were treated with doxycycline (100 mg bid, po) and rifampicin (600 mg qd, po) for 4 weeks. After treatment, the symptoms disappeared quickly, and there was no sign of recurrence or chronic infection. Q fever and Brucella may exist in high-risk practitioners, so we should routinely detect these two pathogens to prevent missed diagnosis.