Clinical and epidemiological use of nested PCR targeting the repetitive element IS1111 associated with the transposase gene from Coxiella burnetii

ABSTRACT Q fever is a worldwide zoonosis caused by Coxiella burnetii—a small obligate intracellular Gram-negative bacterium found in a variety of animals. It is transmitted to humans by inhalation of contaminated aerosols from urine, feces, milk, amniotic fluid, placenta, abortion products, wool, and rarely by ingestion of raw milk from infected animals. Nested PCR can improve the sensitivity and specificity of testing while offering a suitable amplicon size for sequencing. Serial dilutions were performed tenfold to test the limit of detection, and the result was 10× detection of C. burnetti DNA with internal nested PCR primers relative to trans-PCR. Different biological samples were tested and identified only in nested PCR. This demonstrates the efficiency and effectiveness of the primers. Of the 19 samples, which amplify the partial sequence of C. burnetii, 12 were positive by conventional PCR and nested PCR. Seven samples—five spleen tissue samples from rodents and two tick samples—were only positive in nested PCR. With these new internal primers for trans-PCR, we demonstrate that our nested PCR assay for C. burnetii can achieve better results than conventional PCR.

Clinical and epidemiological use of nested PCR targeting the repetitive element IS1111 associated with the transposase gene from Coxiella burnetii.

Q fever is a worldwide zoonosis caused by Coxiella burnetii-a small obligate intracellular Gram-negative bacterium found in a variety of animals. It is transmitted to humans by inhalation of contaminated aerosols from urine, feces, milk, amniotic fluid, placenta, abortion products, wool, and rarely by ingestion of raw milk from infected animals. Nested PCR can improve the sensitivity and specificity of testing while offering a suitable amplicon size for sequencing. Serial dilutions were performed tenfold to test the limit of detection, and the result was 10× detection of C. burnetti DNA with internal nested PCR primers relative to trans-PCR. Different biological samples were tested and identified only in nested PCR. This demonstrates the efficiency and effectiveness of the primers. Of the 19 samples, which amplify the partial sequence of C. burnetii, 12 were positive by conventional PCR and nested PCR. Seven samples-five spleen tissue samples from rodents and two tick samples-were only positive in nested PCR. With these new internal primers for trans-PCR, we demonstrate that our nested PCR assay for C. burnetii can achieve better results than conventional PCR.

Molecular Identification of Q Fever in Patients with a Suspected Diagnosis of Dengue in Brazil in 2013-2014.

Q fever is an important cause of undifferentiated fever that is rarely recognized or reported in Brazil. The objective of this study was to look for the presence of Coxiella burnetii during a dengue fever outbreak in the municipality of Itaboraí, Rio de Janeiro, Brazil, where this bacterium had previously infected humans and domesticated animals. Blood samples from clinically suspected dengue fever patients were tested by polymerase chain reaction (PCR) for C. burnetii; the DNA was detected in nine (3.3%) of 272 patients. One was coinfected with dengue virus, which was also detected in another 166 (61.3%) patients. The nucleotide sequence of PCR amplification and DNA sequencing of the IS1111 transposase elements in the genome of C. burnetii exhibited 99% identity with the sequence in GenBank. The detection of C. burnetii in patients suspected of dengue fever indicates that awareness and knowledge of Q fever should be strengthened and that this bacterium is present in Brazil. Finally, because a negative molecular result does not completely rule out the diagnosis of Q fever and the serological assay based on seroconversion was not available, the actual number of this zoonosis is likely to be much higher than that reported in this study.