Unlocking the Science of Rickettsiology
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Tests offered at ARRL
The ARRL diagnoses diseases using three standard approaches. Examination of the blood for antibodies to specific microorganisms (serology). The detection of a specific DNA segment from the microorganism (molecular). The isolation of the organism using a medium that will sustain and encourage the microorganism to grow (culture). These three areas can be broken down further. In the ARRL, serology is performed using an indirect microimmunofluorescence assay (IFA), an enzyme linked immunosorbent assay (ELISA) and an immunoblot system. The molecular assays are primarily performed by polymerase chain reaction (PCR) and in some instances sequencing is utilised to confirm results. The culture work is performed primarily in cell culture but artificial media is also utilised.
This includes the screening for rickettsia of the spotted fever group (SFG), typhus group (TG) and scrub typhus group (STG). Although STG infections are caused by the genus Orientia, these organisms are closely related to the rickettsia and hence are found in the same cluster. There are three tests offered for the diagnosis of these diseases, namely, an Indirect microimmunofluorescence assay (IFA), polymerase chain reaction (PCR) and culture. For the IFA, Clotted blood (serum) may be submitted for serological diagnosis. If possible a follow-up specimen should be sent a minimum of 7-10 days later to detect a change from negative to a positive antibody level (seroconversion) or if the first sample is positive, a significant increase in antibody levels will also confirm the diagnosis. The PCR involves the detection of a specific DNA targets of the bacterial genome. The culture assay involves the isolation of the organism in cell culture and can take up to six weeks.
Rickettsia
Q fever is caused by the organism Coxiella burnetii. There are three tests offered for the diagnosis of these diseases, namely, an Indirect microimmunofluorescence assay (IFA), polymerase chain reaction (PCR) and culture. For the IFA, Clotted blood (serum) may be submitted for serological diagnosis. If possible a follow-up specimen should be sent a minimum of 7-10 days later to detect a change from negative to a positive antibody level (seroconversion) or if the first sample is positive, a significant increase in antibody levels will also confirm the diagnosis. Q-fever serology involves testing the patient's serum against phase 2 C. burnetii ( acute Q-fever) and phase 1 C. burnetii (chronic Q-fever). The PCR involves the detection of 2 specific DNA targets of the C. burnetii genome. The culture assay involves the isolation of the organism in cell culture and can take up to six weeks.
Q fever
Lyme disease is caused by Borrelia species and is tick transmitted. Our laboratory offers serology, polymerase chain reaction (PCR) and culture for Lyme disease diagnosis. For the serology, serum is examined using three tests for the presence of specific antibody. Our laboratory uses the enzyme linked immunosorbent assay (ELISA) as the primary screening assay and the immunoblot as a secondary or confirmatory assay. PCR is used to directly identify Borrelia species DNA and cultures attempt to isolate the causative organisms and can tale up to six weeks.
Lyme Disease
Neoehrlichia
Neoehlichia species have been detected in 12.9% of Ixodes holocyclus ticks from Australia. Although Neoehlichia species in the northern hemisphere have been shown to cause diseases their pathogeniicity in Australia is currently unknown. As there is no cell cultured isolate for this agent the only diagnostic test that can be offered at this time is PCR.
These diseases are both tick transmitted and although there is evidence that some species exist in Australia the main human pathogens Anaplasma phagocytophilum and Ehrlichia chafeensis are yet to be identified in Australia. For these diseases our laboratory offers IFA, PCR and culture. Our IFA is specific for the above mentioned pathogens, however our PCR will detect most members of these genuses. The culture assays are designed to isolate most of these species.
Anaplasma / Ehrlichia
Babesia
Babesia species are not bacteria, they are in fact protozoa that can be transmitted by tick bite. These agents have been reported from Australia. Our laboratory is currently offering an IFA for the detection of this agent.
Bartonella bacteria cause several diseases in humans. The two most common agents are B. henselae (cat scratch disease) and B. quintana (Trench fever). Our laboratory is currently offering an IFA for the detection of these agents.
Bartonella
Whipples Disease
Whipple's disease is a rare, systemic infectious disease caused by the bacterium Tropheryma whipplei. Commonly considered a gastrointestinal disorder, Whipple's disease primarily causes malabsorption. Our laboratory offers PCR and an IFA test.