Q Fever Detected by Nucleic Acid Amplification

A Loop-Mediated Isothermal Amplification (LAMP) method has been developed for the detection of a specific gene of Coxiella burnetii, the causative agent of Q fever.

It is difficult to distinguish Q fever from other febrile diseases because of the lack of specific clinical manifestations in humans and conventional serodiagnosis requires sera from the acute and convalescent stages of infection, which are unavailable at early diagnosis.

Microbiologists from the Chinese Center for Disease Control and Prevention (Beijing, China) developed the LAMP method, which is a simple, rapid, specific, and cost-effective nucleic acid amplification technique. Between 2007 and 2012, they obtained 24 pairs of blood samples from the acute phase and convalescence of patients with clinical assessment of Q fever. The specificity of the LAMP assay was determined using a total of 42 strains, with 22 strains of the family Rickettsiales, four strains of Anaplasma phagocytophilum, and Ehrlichia chaffeenisis.

A set of universal primers against the repetitive sequence IS1111a of the transposase gene (htpAB) of C. burnetii was designed using PrimerExplorer V4 software and all LAMP reactions were performed with the Loopamp Kit (Eiken Chemical Co., Ltd.; Tokyo, Japan). The primers were based on conserved sequences and synthesized by Sangon Biotech (Shanghai, China). Before being used to determine the specificity of the LAMP assay, each bacterial DNA sample was first prescreened by polymerase chain reaction (PCR) using universal prokaryotic bacterial primers.

The LAMP assay was 100-fold more sensitive than conventional PCR at detecting C. burnetii and a positive result was obtained only for C. burnetii. When testing 24 blood samples from acute stage of clinical assessment Q fever patients, the scientists detected a total of eight positive results by the LAMP assay and two positives by real time PCR. This included five males, age range 29 to 56 years old and 19 females, ages range 16 to 69 years old.

The authors concluded that they had developed a rapid, simple, sensitive, and cost-effective LAMP assay to detect C. burnetii infection in human and domestic animals. Compared with the real time PCR developed in their laboratory, the LAMP assay is a potential tool to support the diagnosis of Q fever in humans and animals in the field, especially in the rural areas of China because of its rapid and sensitive detection without the aid of sophisticated equipment or complicated operations. The study was published on May 16, 2013, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Chinese Center for Disease Control and Prevention
Eiken Chemical Co., Ltd.
Sangon Biotech