DNA microarray-chip based diagnosis of Q-fever (Coxiella burnetii)

Abstract

Coxiella burnetii is an obligate intracellular bacterium causing Q-fever, a zoonotic disease that is ubiquitous throughout the world with the exception of New Zealand. Cattle, goats, sheep and ticks are the primary reservoirs, but many other species, including fish, birds, rodents and cats, are known to become infected. Especially in small ruminants, infection can lead to abortion associated with exceptionally high amounts of C. burnetii in amniotic fluids and the placenta. Furthermore, C. burnetii may be excreted in milk, urine and faeces of infected animals. Human infections frequently follow contact with infected sheep, especially during lambing, or via the inhalation of dried tick faeces during shearing. Most cases of human infection with C. burnetii are self-limiting, associated with fever, fatigue, headache and myalgia. Acute Q-fever is frequently accompanied by atypical pneumonia and ⁄ or hepatitis. Persistence of infection exceeding 6 months in duration is regarded as chronic Q-fever. Commonly, endocarditis is seen, but chronic hepatitis, osteomyelitis, septic arthritis or infection of aneurysm and vascular grafts can also occur. During pregnancy, Q-fever has been associated with premature birth, abortion and neonatal death. Diagnosis mostly relies on serology, but, especially in the early clinical stages, PCR offers substantial benefits for the identification of C. burnetii infection [1]. In our study, we investigated the suitability of a new rapid ‘low cost and density’ (LCD) DNA microarray chip for the detection of C. burnetii (Coxiella 2.5). Besides the commonly used IS1111 genomic target (Genebank accession number: M80806), we coated a recently described genomic marker proposed to be diagnostic of acute Q-fever (acute disease antigen A (adaA), CBU_0952, GenBank ID AAO90475.1) on the chip [2]. The results were compared with those of both conventional, gel-based and a real-time LightCyclerHyprobe– PCR assay in terms of specificity and sensitivity. Clinical materials of both human and animal origin were also used for evaluation.