Fluorescence in situ hybridization for detecting Coxiella burnetii in tissue samples from chronic Q fever patients

Objective: Detection of the intracellular bacterium Coxiella burnetii, causative agent of chronic Q fever, is notoriously difficult. Diagnosis of and duration of antibiotic treatment for chronic Q fever is partly determined by detection of the bacterium with polymerase chain reaction (PCR). Fluorescence in situ hybridization (FISH) might be a promising technique for detecting C. burnetii in tissue samples from chronic Q fever patients, but its value in comparison with PCR is uncertain. We aim to assess the value of FISH for detecting C. burnetii in tissue of chronic Q fever patients. Methods: FISH and PCR were performed on tissue samples from Dutch chronic Q fever patients collected during surgery or autopsy. Sensitivity, specificity, and overall diagnostic accuracy were calculated. Additionally, data on patient and disease characteristics were collected from electronic medical records. Results: In total, 49 tissue samples from mainly vascular walls, heart valves, or placentas, obtained from 39 chronic Q fever patients, were examined by FISH and PCR. The sensitivity and specificity of FISH compared to PCR for detecting C. burnetii in tissue samples from chronic Q fever patients was 45.2% (95% confidence interval (CI), 27.3% - 64.0%) and 84.6% (95% CI, 54.6% - 98.1%), respectively. The overall diagnostic accuracy was 56.8% (95% CI, 42.2% - 72.3%). Two C. burnetii PCR negative placentas were FISH positive. Four FISH results (8.2%) were deemed inconclusive because of autofluorescence. Conclusion: With an overall diagnostic accuracy of 57.8%, we conclude that FISH has limited value in the routine diagnostics of chronic Q fever. (c) 2022 The Authors. Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases.

Automated summary

This study assesses the value of fluorescence in situ hybridization (FISH) for detecting Coxiella burnetii in tissue samples from chronic Q fever patients. The results indicate that FISH has limited sensitivity and specificity, and its value in routine diagnostics for chronic Q fever is limited.