Comparison of three protocols to preserve Leptospira spp. in cat urine for efficient DNA extraction and PCR amplification

ABSTRACT

Background: The pathogenic leptospira infection in mammalian species can cause a range of acute or chronic manifestations and may result in a carrier state. Previous studies have suggested that cats were resistant to acute leptospirosis however, the description of some clinical cases suggests that Leptospira spp. may also be pathogenic to this species. Recentstudies have shown that leptospires may be shed in the urine of infected cats. Endogenous substances present in urine mayinhibit PCR and allow leptospires to evade detection. This study aims to compare three protocols for sample processingto optimize the detection of pathogenic leptospires in cat urine.Materials, Methods & Results: Three protocols to optimize the detection of pathogenic leptospires in cat urine were tested.Aliquots of standard concentration of L. interrogans serovar Canicola culture were added to urine samples to achieveconcentrations of 1×105 to 1×102 leptospires/mL for each protocol. In protocols A and B the urine was neutralized by theaddition of phosphate-buffered saline (PBS), pH 7.4, in a proportion of 1 PBS 2.5 urine (v/v). In protocol A, PBS wasadded to neutralize the urine pH for the leptospiral organisms immediately after addition of leptospires. In protocol B,PBS was added just before DNA extraction. In protocol C, no PBS was added. DNA extraction was performed at 4, 24and 48 h after addition of the leptospires using a modified protocol. Samples were incubated at 37ºC for 10 min. Sampleswere then centrifuged (850 g) for 15 min, at 25ºC. The supernatants were transferred to another tube, and the pellets werediscarded. The supernatants were centrifuged (16060 g) for 20 min at 4ºC. The supernatants were then discarded, and thepellets resuspended and washed with 1000 µL of PBS. All the samples were centrifuged at 16060 g for an additional 20min at 25ºC. The supernatants were discarded and the pellets were resuspended in 100 µL of PBS and incubated at 94ºCfor...(AU)