A Novel Real Time PCR Assay for the Detection of Babesia microti in a Highly Endemic Area Using Luminex Aries System

BACKGROUND: Babesiosis is a tick-borne infection of erythrocytes caused by parasites of the genus Babesia. In United States most of the reported cases occur in the Northeast and upper Midwestern states, New York being an endemic area. Majority of the cases in the United States is due to infection with Babesia microti. Most patients with babesiosis are asymptomatic or have a mild illness, but some may develop fatal illness. Current laboratory diagnosis of Babesiosis including parasitemia is by microscopic demonstration of intraerythrocytic Babesia parasites in blood films which requires specially trained personnel. We have developed a simple and rapid PCR assay for the detection of B. microti 18S rRNA gene (BMPCR) which can be used as an alternative screening assay. METHODS: BMPCR assay was developed based on Luminex Multicode technology using Luminex Aries instrument and in-house developed primers. Babesia positive clinical samples confirmed by NY State Department of Health and clinical samples negative for Babesia were used to determine accuracy. Specificity was evaluated using malaria positive samples, several bacterial isolates, selected B. microti strains and other Babesia species. Limit of Detection was determined using known copies of B. microti DNA. Reproducibility of the assay was assessed by testing samples on different days and runs by different analysts. RESULTS: Accuracy of the BMPCR assay was 100% for the 30 Babesia positive and 30 negative samples. All B. microti ATCC strains were positive by BMPCR. 95% LOD of the assay as determined by probit analysis was 1177 copies/50µl of blood. Sensitivity of the assay was higher than that of microscopic detection and specificity was 100%. No cross reactivity was observed with any of the malarial species tested. Babesia MO1, Babesia duncani and all bacterial isolates tested were negative by the BMPCR. Intra-run, inter-run and day to day reproducibility of the assay was 100%. CONCLUSION: The B. microti real time PCR assay developed by Northwell Health Laboratories is rapid, sensitive, specific and reproducible. With the sample to result turnaround time of 2.5 hours and hands on time of only 5 minutes per sample, BMPCR can be used as screening assay for B. microti in clinical laboratories. DISCLOSURES: All authors: No reported disclosures.