AVALIAÇÃO DE MÉTODOS DE DESCONTAMINAÇÃO PARA OBTENÇÃO DE CULTURAS PURAS DE LEPTOSPIRAS A PARTIR DE AMOSTRAS MISTAS COM Spirillum spp.

Abstract

It is challenging to obtain pure cultures of Leptospira from environmental samples, mainly due to the presence of accompanying microbiota that can contaminate cultures, highlighting bacteria of the genus Spirillum that have characteristics similar to leptospires. Thus, cannot be eliminated by the most common decontamination techniques during leptospires isolation process. The purpose of this study was to evaluate five decontamination methods to obtain pure cultures of Leptospira from mixed samples with Spirillum spp. We collected ten samples from untreated domestic sewage dumped of to streets in Macapa city – Brazilian Amazon, and submitted to bacteriological culture for Leptospira isolation. The presence of leptospires was confirmed by visualization under dark-field microscopy and by 16S PCR. In the samples in which Spirillum was observed, five methods of decontamination were tested: 1 – Membrane filtration (0.20 μm and 0.22 μm); 2- Culture in selective medium for Leptospira spp.; 3- Centrifugation; 4- Serial dilution and 5- Plating on solid EMJH medium. Out of all 10 samples, five were positive for leptospires and in three there was the simultaneous detection of leptospires and Spirillum . Plating on solid EMJH medium (5) was the most efficient method, decontaminating all three mixed cultures. Only one culture was decontaminated by the technique of culture in selective medium for Leptospira spp. (2), and the other methods were ineffective. In conclusion, plating on solid EMJH medium method can be used to obtain pure cultures of Leptospira spp. from environmental samples containing Spirillum spp. Keywords: Leptospira; decontamination; mixed cultures; Spirillum .