Detection of leptospires in urine by PCR for early diagnosis of leptospirosis

Abstract

We tested urine samples from patients at different stages of current leptospirosis and thereafter to determine whether use of the PCR for detection of leptospires in urine can be a valuable alternative to culturing. The procedure of DNA extraction and subsequent PCR applied to 15 freshly voided urine samples proved to be twice as sensitive as culturing. Overall, we were able to detect leptospires in approximately 90% (26 of 29) of the urine samples. Urine and serum samples were obtained from seven patients, before the eighth day of illness. Although it is generally assumed that leptospiruria starts approximately in the second week of illness, we were able to detect leptospires in all of these early urine samples. In contrast, only two of seven corresponding serum samples gave positive PCR results, which suggests that PCR analysis of urine can be more successful for early diagnosis of leptospirosis than PCR analysis of serum. Urine samples from six patients who had been treated with antibiotics at the time of illness were positive by PCR, implying that the patients were still shedding leptospires in their urine despite treatment. Some of these samples were even taken years after the infection, indicating that shedding of leptospires in urine may last much longer than is generally assumed. We conclude that detection of leptospires in urine with PCR is a promising approach for early diagnosis of leptospirosis and may also be useful in studying long-term shedding.